Browse Source

Now uses -ms macros

ceriel 31 years ago
parent
commit
5e2915512f
19 changed files with 647 additions and 667 deletions
  1. 1 3
      doc/em/.distr
  2. 0 3
      doc/em/READ_ME
  3. 73 89
      doc/em/app.codes.nr
  4. 10 12
      doc/em/app.exam.nr
  5. 134 137
      doc/em/assem.nr
  6. 4 6
      doc/em/cont.nr
  7. 34 43
      doc/em/descr.nr
  8. 42 43
      doc/em/dspace.nr
  9. 10 0
      doc/em/em.i
  10. 47 66
      doc/em/env.nr
  11. 25 34
      doc/em/intro.nr
  12. 11 16
      doc/em/ispace.nr
  13. 68 88
      doc/em/mach.nr
  14. 97 23
      doc/em/macr.nr
  15. 27 38
      doc/em/mapping.nr
  16. 9 9
      doc/em/mem.nr
  17. 3 8
      doc/em/title.nr
  18. 28 30
      doc/em/traps.nr
  19. 24 19
      doc/em/types.nr

+ 1 - 3
doc/em/.distr

@@ -1,9 +1,7 @@
-Makefile
+proto.make
 READ_ME
-addend.n
 app.codes.nr
 app.exam.nr
-app.int.nr
 assem.nr
 cont.nr
 descr.nr

+ 0 - 3
doc/em/READ_ME

@@ -3,7 +3,4 @@ DESCRIPTION OF A MACHINE ARCHITECTURE FOR USE WITH BLOCK STRUCTURED LANGUAGES
 
 The file em.i (text of the defining interpreter) was hand-edited from int/em.p
 
-To print, set NROFF and TBL in the Makefile and call  make.
-It uses the kun macro package which is also distributed.
-
 The directory int contains the interpreter.

+ 73 - 89
doc/em/app.codes.nr

@@ -1,4 +1,4 @@
-.BP
+.bp
 .AP "EM CODE TABLES"
 The following table is used by the assembler for EM machine
 language.
@@ -10,65 +10,66 @@ Each line describes a range of interpreter opcodes by
 specifying for which instruction the range is used, the type of the
 opcodes (mini, shortie, etc..) and range for the instruction
 argument.
-.A
+.QQ
 The first field on each line gives the EM instruction mnemonic,
 the second field gives some flags.
 If the opcodes are minis or shorties the third field specifies
 how many minis/shorties are used.
 The last field gives the number of the (first) interpreter
 opcode.
-.N 1
+.LP
 Flags :
-.IS 3
-.N 1
+.IP ""
 Opcode type, only one of the following may be specified.
-.PS - 5 "  "
-.PT \-
+.RS
+.IP \-
 opcode without argument
-.PT m
+.IP m
 mini
-.PT s
+.IP s
 shortie
-.PT 2
+.IP 2
 opcode with 2-byte signed argument
-.PT 4
+.IP 4
 opcode with 4-byte signed argument
-.PT 8
+.IP 8
 opcode with 8-byte signed argument
-.PT u
+.IP u
 opcode with 2-byte unsigned argument
-.PE
+.RE
+.IP ""
 Secondary (escaped) opcodes.
-.PS - 5 "  "
-.PT e
+.RS
+.IP e
 The opcode thus marked is in the secondary opcode group instead
 of the primary
-.PE
+.RE
+.IP ""
 restrictions on arguments
-.PS - 5 "  "
-.PT N
+.RS
+.IP N
 Negative arguments only
-.PT P
+.IP P
 Positive and zero arguments only
-.PE
+.RE
+.IP ""
 mapping of arguments
-.PS - 5 "  "
-.PT w
+.RS
+.IP w
 argument must be divisible by the wordsize and is divided by the
 wordsize before use as opcode argument.
-.PT o
+.IP o
 argument ( possibly after division ) must be >= 1 and is
 decremented before use as opcode argument
-.PE
-.IE
+.RE
+.LP
 If the opcode type is 2,4 or 8 the resulting argument is used as
 opcode argument (least significant byte first).
-.N
 If the opcode type is mini, the argument is added
 to the first opcode \- if in range \- .
 If the argument is negative, the absolute value minus one is
 used in the algorithm above.
-.N
+.br
 For shorties with positive arguments the first opcode is used
 for arguments in the range 0..255, the second for the range
 256..511, etc..
@@ -78,30 +79,32 @@ for arguments in the range \-1..\-256, the second for the range
 The byte following the opcode contains the least significant
 byte of the argument.
 First some examples of these specifications.
-.PS - 5
-.PT "aar mwPo 1 34"
+.IP "aar mwPo 1 34"
+.br
 Indicates that opcode 34 is used as a mini for Positive
 instruction arguments only.
 The w and o indicate division and decrementing of the
 instruction argument.
-Because the resulting argument must be zero ( only opcode 34 may be used
-), this mini can only be used for instruction argument 2.
+Because the resulting argument must be zero ( only opcode 34 may be used),
+this mini can only be used for instruction argument 2.
 Conclusion: opcode 34 is for "AAR 2".
-.PT "adp sP 1 41"
+.IP "adp sP 1 41"
+.br
 Opcode 41 is used as shortie for ADP with arguments in the range
 0..255.
-.PT "bra sN 2 60"
+.IP "bra sN 2 60"
+.br
 Opcode 60 is used as shortie for BRA with arguments \-1..\-256,
 61 is used for arguments \-257..\-512.
-.PT "zer e\- 145"
+.IP "zer e\- 145"
+.br
 Escaped opcode 145 is used for ZER.
-.PE
+.LP
 The interpreter opcode table:
-.N 1
-.IS 3
+.DS
 .so itables
-.IE
-.P
+.DE
+.PP
 The table above results in the following dispatch tables.
 Dispatch tables are used by interpreters to jump to the
 routines implementing the EM instructions, indexed by the next opcode.
@@ -110,60 +113,41 @@ of eight consecutive opcodes, preceded by the first opcode number
 on that line.
 Routine names consist of an EM mnemonic followed by a suffix.
 The suffices show the encoding used for each opcode.
-.N
+.LP
 The following suffices exist:
-.N 1
-.VS 1 0
-.IS 4
-.PS - 11
-.PT .z
-no arguments
-.PT .l
-16-bit argument
-.PT .L
-32-bit argument
-.PT .u
-16-bit unsigned argument
-.PT .lw
-16-bit argument divided by the wordsize
-.PT .Lw
-32-bit argument divided by the wordsize
-.PT .p
-positive 16-bit argument
-.PT .P
-positive 32-bit argument
-.PT .pw
-positive 16-bit argument divided by the wordsize
-.PT .Pw
-positive 32-bit argument divided by the wordsize
-.PT .n
-negative 16-bit argument
-.PT .N
-negative 32-bit argument
-.PT .nw
-negative 16-bit argument divided by the wordsize
-.PT .Nw
-negative 32-bit argument divided by the wordsize
-.PT .s<num>
-shortie with <num> as high order argument byte
-.PT .w<num>
-shortie with argument divided by the wordsize
-.PT .<num>
-mini with <num> as argument
-.PT .<num>W
-mini with <num>*wordsize as argument
-.PE 1
+.TS
+tab(:);
+l l.
+.z:no arguments
+.l:16-bit argument
+.L:32-bit argument
+.u:16-bit unsigned argument
+.lw:16-bit argument divided by the wordsize
+.Lw:32-bit argument divided by the wordsize
+.p:positive 16-bit argument
+.P:positive 32-bit argument
+.pw:positive 16-bit argument divided by the wordsize
+.Pw:positive 32-bit argument divided by the wordsize
+.n:negative 16-bit argument
+.N:negative 32-bit argument
+.nw:negative 16-bit argument divided by the wordsize
+.Nw:negative 32-bit argument divided by the wordsize
+.s<num>:shortie with <num> as high order argument byte
+.w<num>:shortie with argument divided by the wordsize
+.<num>:mini with <num> as argument
+.<num>W:mini with <num>*wordsize as argument
+.TE
+.LP
 <num> is a possibly negative integer.
-.VS
-.IE
+.LP
 The dispatch table for the 256 primary opcodes:
-.N 1
+.sp 1
 .so dispat1
-.N 2
+.sp 2
 The list of secondary opcodes (escape1):
-.N 1
+.sp 1
 .so dispat2
-.N 2
+.sp 2
 Finally, the list of opcodes with four byte arguments (escape2).
-.N 1
+.sp 1
 .so dispat3

+ 10 - 12
doc/em/app.exam.nr

@@ -1,7 +1,7 @@
-.BP
+.bp
 .AP "AN EXAMPLE PROGRAM"
-.A 1 0
-.NA
+.PP
+.na
 .ta 4n 8n 12n 16n 20n
 .nf
  1	program example(output);
@@ -45,12 +45,12 @@
 39		test(r)
 40	end.
 .fi
-.AD
-.BP
+.ad
+.bp
 The EM code as produced by the Pascal-VU compiler is given below. Comments
 have been added manually.  Note that this code has already been  optimized.
-.A 1 0
-.NA
+.LP
+.na
 .nf
 .ta 1n 24n
 	mes 2,2,2	; wordsize 2, pointersize 2
@@ -231,14 +231,13 @@ have been added manually.  Note that this code has already been  optimized.
 	end 0
 	mes 5	; reals were used
 .fi
-.AD
-.A 1 0
+.ad
+.PP
 The compact code corresponding to the above program is listed below.
 Read it horizontally, line by line, not column by column.
 Each number represents a byte of compact code, printed in decimal.
 The first two bytes form the magic word.
-.N 1
-.IS 3
+.LP
 .Dr 33
  173   0 159 122 122 122 255 242   1 161 250 124 116  46 112   0
  255 156 245  40   2 245   0 128 120 155 249 123 115 117 109 160
@@ -274,4 +273,3 @@ The first two bytes form the magic word.
  116   8 122  69 120  20 249 124  95 104 108 116   8 122 152 120
  159 124 160 255 159 125 255
 .De
-.IE

+ 134 - 137
doc/em/assem.nr

@@ -1,6 +1,6 @@
-.BP
-.SN 11
-.S1 "EM ASSEMBLY LANGUAGE"
+.bp
+.P1 "EM ASSEMBLY LANGUAGE"
+.PP
 We use two representations for assembly language programs,
 one is in ASCII and the other is the compact assembly language.
 The latter needs less space than the first for the same program
@@ -16,7 +16,8 @@ The last part lists the EM instructions with the type of
 arguments allowed and an indication of the function.
 Appendix A gives a detailed description of the effect of all
 instructions in the form of a Pascal program.
-.S2 "ASCII assembly language"
+.P2 "ASCII assembly language"
+.PP
 An assembly language program consists of a series of lines, each
 line may be blank, contain one (pseudo)instruction or contain one
 label.
@@ -25,13 +26,13 @@ Upper case is used in this
 document merely to distinguish keywords from the surrounding prose.
 Comment is allowed at the end of each line and starts with a semicolon ";".
 This kind of comment does not exist in the compact form.
-.A
+.QQ
 Labels must be placed all by themselves on a line and start in
 column 1.
 There are two kinds of labels, instruction and data labels.
 Instruction labels are unsigned positive integers.
 The scope of an instruction label is its procedure.
-.A
+.QQ
 The pseudoinstructions CON, ROM and BSS may be preceded by a
 line containing a
 1\-8 character data label, the first character of which is a
@@ -46,13 +47,13 @@ These labels are considered as a special case and handled
 more efficiently in compact assembly language (see below).
 Note that a data label on its own or two consecutive labels are not
 allowed.
-.P
+.PP
 Each statement may contain an instruction mnemonic or pseudoinstruction.
 These must begin in column 2 or later (not column 1) and must be followed
 by a space, tab, semicolon or LF.
 Everything on the line following a semicolon is
 taken as a comment.
-.P
+.PP
 Each input file contains one module.
 A module may contain many procedures,
 which may be nested.
@@ -62,14 +63,15 @@ collection of instructions and pseudoinstructions and finally an END
 statement.
 Pseudoinstructions are also allowed between procedures.
 They do not belong to a specific procedure.
-.P
+.PP
 All constants in EM are interpreted in the decimal base.
 The ASCII assembly language accepts constant expressions
 wherever constants are allowed.
 The operators recognized are: +, \-, *, % and / with the usual
 precedence order.
 Use of the parentheses ( and ) to alter the precedence order is allowed.
-.S3 "Instruction arguments"
+.P3 "Instruction arguments"
+.PP
 Unlike many other assembly languages, the EM assembly
 language requires all arguments of normal and pseudoinstructions
 to be either a constant or an identifier, but not a combination
@@ -87,7 +89,7 @@ It is not allowed to add or subtract from instruction labels or procedure
 identifiers,
 which certainly is not a severe restriction and greatly aids
 optimization.
-.P
+.PP
 Instruction arguments can be constants,
 data labels, data labels offsetted by a constant, instruction
 labels and procedure identifiers.
@@ -98,7 +100,7 @@ that fit in a word.
 Arguments used as offsets to pointers should fit in a
 pointer-sized integer.
 Finally, arguments to LDC should fit in a double-word integer.
-.P
+.PP
 Several instructions have two possible forms:
 with an explicit argument and with an implicit argument on top of the stack.
 The size of the implicit argument is the wordsize.
@@ -109,7 +111,7 @@ integers on top of the stack are to be compared.
 on top of the stack that specifies the size of the integers to
 be compared.
 Thus the following two sequences are equivalent:
-.N 1
+.KS
 .TS
 center, tab(:) ;
 l r 30 l r.
@@ -118,16 +120,18 @@ LDL:\-14:LDL:\-14
 ::LOC:4
 CMI:4:CMI:
 ZEQ:*1:ZEQ:*1
-.TE 1
+.TE
+.KE
 Section 11.1.6 shows the arguments allowed for each instruction.
-.S3 "Pseudoinstruction arguments"
+.P3 "Pseudoinstruction arguments"
+.PP
 Pseudoinstruction arguments can be divided in two classes:
 Initializers and others.
 The following initializers are allowed: signed integer constants,
 unsigned integer constants, floating-point constants, strings,
 data labels, data labels offsetted by a constant, instruction
 labels and procedure identifiers.
-.P
+.PP
 Constant initializers in BSS, HOL, CON and ROM pseudoinstructions
 can be followed by a letter I, U or F.
 This indicator
@@ -142,10 +146,9 @@ As in instruction arguments, initializers include expressions of the form:
 \&"LABEL+offset" and "LABEL\-offset".
 The offset must be an unsigned decimal constant.
 The 'IUF' indicators cannot be used in the offsets.
-.P
+.PP
 Data labels are referred to by their name.
-.P
-
+.PP
 Strings are surrounded by double quotes (").
 Semicolon's in string do not indicate the start of comment.
 In the ASCII representation the escape character \e (backslash)
@@ -153,7 +156,6 @@ alters the meaning of subsequent character(s).
 This feature allows inclusion of zeroes, graphic characters and
 the double quote in the string.
 The following escape sequences exist:
-.DS
 .TS
 center, tab(:);
 l l l.
@@ -166,7 +168,6 @@ backslash:\e:\e\e
 double quote:":\e"
 bit pattern:\fBddd\fP:\e\fBddd\fP
 .TE
-.DE
 The escape \fB\eddd\fP consists of the backslash followed by 1,
 2, or 3 octal digits specifying the value of
 the desired character.
@@ -176,17 +177,18 @@ the backslash is ignored.
 Example: CON "hello\e012\e0".
 Each string element initializes a single byte.
 The ASCII character set is used to map characters onto values.
-.P
+.PP
 Instruction labels are referred to as *1, *2, etc.  in both branch
 instructions and as initializers.
-.P
+.PP
 The notation $procname means the identifier for the procedure
 with the specified name.
 This identifier has the size of a pointer.
-.S3 Notation
+.P3 Notation
+.PP
 First, the notation used for the arguments, classes of
 instructions and pseudoinstructions.
-.IS 2
+.DS
 .TS
 tab(:);
 l l l.
@@ -204,9 +206,10 @@ l l l.
 <...>+:\&=:one or more of <...>
 [...]:\&=:optional ...
 .TE
-.IE
-.S3 "Pseudoinstructions"
-.S4 "Storage declaration"
+.DE
+.P3 "Pseudoinstructions"
+.P4 "Storage declaration"
+.PP
 Initialized global data is allocated by the pseudoinstruction CON,
 which needs at least one argument.
 Each argument is used to allocate and initialize a number of
@@ -215,7 +218,7 @@ The number of bytes to be allocated and the alignment depend on the type
 of the argument.
 For each argument, an integral number of words,
 determined by the argument type, is allocated and initialized.
-.P
+.PP
 The pseudoinstruction ROM is the same as CON,
 except that it guarantees that the initialized words
 will not change during the execution of the program.
@@ -223,7 +226,7 @@ This information allows optimizers to do
 certain calculations such as array indexing and
 subrange checking at compile time instead
 of at run time.
-.P
+.PP
 The pseudoinstruction BSS allocates
 uninitialized global data or large blocks of data initialized
 by the same value.
@@ -239,14 +242,14 @@ the second byte by 1 etc. in assembly language.
 The assembler/loader adds the base address of
 the HOL block to these numbers to obtain the
 absolute address in the machine language.
-.P
+.PP
 The scope of a HOL block starts at the HOL pseudo and
 ends at the next HOL pseudo or at the end of a module
 whatever comes first.
 Each instruction falls in the scope of at most one
 HOL block, the current HOL block.
 It is not allowed to have more than one HOL block per procedure.
-.P
+.PP
 The alignment restrictions are enforced by the
 pseudoinstructions.
 All initializers are aligned on a multiple of their size or the wordsize
@@ -257,52 +260,51 @@ Switching to another type of fragment or placing a label forces
 word-alignment.
 There are three types of fragments in global data space: CON, ROM and
 BSS/HOL.
-.N 1
-.IS 2
-.PS - 4
-.PT "BSS <cst1>,<val>,<cst2>"
+.IP "BSS <cst1>,<val>,<cst2>"
+.br
 Reserve <cst1> bytes.
 <val> is the value used to initialize the area.
 <cst1> must be a multiple of the size of <val>.
 <cst2> is 0 if the initialization is not strictly necessary,
 1 if it is.
-.PT "HOL <cst1>,<val>,<cst2>"
+.IP "HOL <cst1>,<val>,<cst2>"
+.br
 Idem, but all following absolute global data references will
 refer to this block.
 Only one HOL is allowed per procedure,
 it has to be placed before the first instruction.
-.PT "CON <val>+"
+.IP "CON <val>+"
+.br
 Assemble global data words initialized with the <val> constants.
-.PT "ROM <val>+"
+.IP "ROM <val>+"
+.br
 Idem, but the initialized data will never be changed by the program.
-.PE
-.IE
-.S4 "Partitioning"
+.P4 "Partitioning"
+.PP
 Two pseudoinstructions partition the input into procedures:
-.IS 2
-.PS - 4
-.PT "PRO <pro>[,<cst>]"
+.IP "PRO <pro>[,<cst>]"
+.br
 Start of procedure.
 <pro> is the procedure name.
 <cst> is the number of bytes for locals.
 The number of bytes for locals must be specified in the PRO or
 END pseudoinstruction.
 When specified in both, they must be identical.
-.PT "END  [<cst>]"
+.IP "END  [<cst>]"
+.br
 End of Procedure.
 <cst> is the number of bytes for locals.
 The number of bytes for locals must be specified in either the PRO or
 END pseudoinstruction or both.
-.PE
-.IE
-.S4 "Visibility"
+.P4 "Visibility"
+.PP
 Names of data and procedures in an EM module can either be
 internal or external.
 External names are known outside the module and are used to link
 several pieces of a program.
 Internal names are not known outside the modules they are used in.
 Other modules will not 'see' an internal name.
-.A
+.QQ
 To reduce the number of passes needed,
 it must be known at the first occurrence whether
 a name is internal or external.
@@ -312,47 +314,51 @@ If the first occurrence of a name is a reference,
 the name is considered to be external.
 If the first occurrence is in one of the following pseudoinstructions,
 the effect of the pseudo has precedence.
-.IS 2
-.PS - 4
-.PT "EXA <dlb>"
+.IP "EXA <dlb>"
+.br
 External name.
 <dlb> is known, possibly defined, outside this module.
 Note that <dlb> may be defined in the same module.
-.PT "EXP <pro>"
+.IP "EXP <pro>"
+.br
 External procedure identifier.
 Note that <pro> may be defined in the same module.
-.PT "INA <dlb>"
+.IP "INA <dlb>"
+.br
 Internal name.
 <dlb> is internal to this module and must be defined in this module.
-.PT "INP <pro>"
+.IP "INP <pro>"
+.br
 Internal procedure.
 <pro> is internal to this module and must be defined in this module.
-.PE
-.IE
-.S4 "Miscellaneous"
+.P4 "Miscellaneous"
+.PP
 Two other pseudoinstructions provide miscellaneous features:
-.IS 2
-.PS - 4
-.PT "EXC <cst1>,<cst2>"
+.IP "EXC <cst1>,<cst2>"
+.br
 Two blocks of instructions preceding this one are
 interchanged before being processed.
 <cst1> gives the number of lines of the first block.
 <cst2> gives the number of lines of the second one.
 Blank and pure comment lines do not count.
 This instruction is obsolete. Its use is strongly discouraged.
-.PT "MES <cst>[,<par>]*"
+.IP "MES <cst>[,<par>]*"
+.br
 A special type of comment.
 Used by compilers to communicate with the
 optimizer, assembler, etc. as follows:
-.VS 1 0
-.PS - 4
-.PT "MES 0"
+.RS
+.IP "MES 0"
+.br
 An error has occurred, stop further processing.
-.PT "MES 1"
+.IP "MES 1"
+.br
 Suppress optimization.
-.PT "MES 2,<cst1>,<cst2>"
+.IP "MES 2,<cst1>,<cst2>"
+.br
 Use wordsize <cst1> and pointer size <cst2>.
-.PT "MES 3,<cst1>,<cst2>,<cst3>,<cst4>"
+.IP "MES 3,<cst1>,<cst2>,<cst3>,<cst4>"
+.br
 Indicates that a local variable is never referenced indirectly.
 Used to indicate that a register may be used for a specific
 variable.
@@ -361,51 +367,57 @@ and offset from LB if negative.
 <cst2> gives the size of the variable.
 <cst3> indicates the class of the variable.
 The following values are currently recognized:
-.PS
-.PT 0
-The variable can be used for anything.
-.PT 1
-The variable is used as a loopindex.
-.PT 2
-The variable is used as a pointer.
-.PT 3
-The variable is used as a floating point number.
-.PE 0
+.br
+0\0\0\0The variable can be used for anything.
+.br
+1\0\0\0The variable is used as a loopindex.
+.br
+2\0\0\0The variable is used as a pointer.
+.br
+3\0\0\0The variable is used as a floating point number.
+.br
 <cst4> gives the priority of the variable,
 higher numbers indicate better candidates.
-.PT "MES 4,<cst>,<str>"
+.IP "MES 4,<cst>,<str>"
+.br
 Number of source lines in file <str> (for profiler).
-.PT "MES 5"
+.IP "MES 5"
+.br
 Floating point used.
-.PT "MES 6,<val>*"
+.IP "MES 6,<val>*"
+.br
 Comment.  Used to provide comments in compact assembly language.
-.PT "MES 7,....."
+.IP "MES 7,....."
+.br
 Reserved.
-.PT "MES 8,<pro>[,<dlb>]..."
+.IP "MES 8,<pro>[,<dlb>]..."
+.br
 Library module. Indicates that the module may only be loaded
 if it is useful, that is, if it can satisfy any unresolved
 references during the loading process.
 May not be preceded by any other pseudo, except MES's.
-.PT "MES 9,<cst>"
+.IP "MES 9,<cst>"
+.br
 Guarantees that no more than <cst> bytes of parameters are
 accessed, either directly or indirectly.
-.PT "MES 10,<cst>[,<par>]*
+.IP "MES 10,<cst>[,<par>]*
+.br
 This message number is reserved for the global optimizer.
 It inserts these messages in its output as hints to backends.
 <cst> indicates the type of hint.
-.PT "MES 11"
+.IP "MES 11"
+.br
 Procedures containing this message are possible destinations of
 non-local goto's with the GTO instruction.
 Some backends keep locals in registers,
 the locals in this procedure should not be kept in registers and
 all registers containing locals of other procedures should be
 saved upon entry to this procedure.
-.PE 1
-.VS
+.RE
+.IP ""
 Each backend is free to skip irrelevant MES pseudos.
-.PE
-.IE
-.S2 "The Compact Assembly Language"
+.P2 "The Compact Assembly Language"
+.PP
 The assembler accepts input in a highly encoded form.
 This
 form is intended to reduce the amount of file transport between the
@@ -414,16 +426,14 @@ and back ends, and also reduces the amount of storage required for storing
 libraries.
 Libraries are stored as archived compact assembly language, not machine
 language.
-.P
+.PP
 When beginning to read the input, the assembler is in neutral state, and
 expects either a label or an instruction (including the pseudoinstructions).
 The meaning of the next byte(s) when in neutral state is as follows, where
 b1, b2
 etc. represent the succeeding bytes.
-.N 1
-.DS
 .TS
-tab(:) ;
+tab(:);
 rw17 4 l.
 0:Reserved for future use
 1\-129:Machine instructions, see Appendix A, alphabetical list
@@ -433,38 +443,31 @@ rw17 4 l.
 180\-239:Instruction labels 0 \- 59  (180 is local label 0 etc.)
 240\-244:See the Common Table below
 245\-255:Not used
-.TE 1
-.DE 0
+.TE
 After a label, the assembler is back in neutral state; it can immediately
 accept another label or an instruction in the next byte.
 No linefeeds are used to separate lines.
-.P
+.PP
 If an opcode expects no arguments,
 the assembler is back in neutral state after
 reading the one byte containing the instruction number.
 If it has one or
 more arguments (only pseudos have more than 1), the arguments follow directly,
 encoded as follows:
-.N 1
-.IS 2
 .TS
 tab(:);
 r l.
 0\-239:Offsets from \-120 to 119
-
 240\-255:See the Common Table below
-.TE 1
+.TE
 Absence of an optional argument is indicated by a special
 byte.
-.IE 2
-.NE 7
-.CS
-Common Table for Neutral State and Arguments
-.CE
 .TS
 tab(:);
+c s s s
 c c s c
 l4 l l4 l.
+Common Table for Neutral State and Arguments
 class:bytes:description
 
 <ilb>:240:b1:Instruction label b1  (Not used for branches)
@@ -486,7 +489,7 @@ class:bytes:description
 <end>:255::Delimiter for argument lists or
 :::indicates absence of optional argument
 .TE 1
-.P
+.PP
 The bytes specifying the value of a 16, 32 or 64 bit constant
 are presented in two's complement notation, with the least
 significant byte first. For example: the value of a 32 bit
@@ -494,25 +497,22 @@ constant is ((s4*256+b3)*256+b2)*256+b1, where s4 is b4\-256 if
 b4 is greater than 128 else s4 takes the value of b4.
 A <string> consists of a <cst> immediately followed by
 a sequence of bytes with length <cst>.
-.P
+.PP
 .ne 8
 The pseudoinstructions fall into several categories, depending on their
 arguments:
-.N 1
 .DS
- Group 1 \- EXC, BSS, HOL have a known number of arguments
- Group 2 \- EXA, EXP, INA, INP have a string as argument
- Group 3 \- CON, MES, ROM have a variable number of various things
- Group 4 \- END, PRO have a trailing optional argument.
-.DE 1
+Group 1 \- EXC, BSS, HOL have a known number of arguments
+Group 2 \- EXA, EXP, INA, INP have a string as argument
+Group 3 \- CON, MES, ROM have a variable number of various things
+Group 4 \- END, PRO have a trailing optional argument.
+.DE
 Groups 1 and 2
 use the encoding described above.
 Group 3 also uses the encoding listed above, with an <end> byte after the
 last argument to indicate the end of the list.
 Group 4 uses
 an <end> byte if the trailing argument is not present.
-.N 2
-.IS 2
 .TS
 tab(|);
 l s l
@@ -523,18 +523,17 @@ Example  ASCII|Example compact
 
 2||182
 1||181
- LOC|10|69 130
- LOC|\-10|69 110
- LOC|300|69 245 44 1
- BRA|*19|18 139
+\0LOC|10|69 130
+\0LOC|\-10|69 110
+\0LOC|300|69 245 44 1
+\0BRA|*19|18 139
 300||241 44 1
 .3||242 3
- CON|4,9,*2,$foo|151 124 129 240 2 249 123 102 111 111 255
- CON|.35|151 242 35 255
-.TE 0
-.IE 0
-.S2 "Assembly language instruction list"
-.P
+\0CON|4,9,*2,$foo|151 124 129 240 2 249 123 102 111 111 255
+\0CON|.35|151 242 35 255
+.TE
+.P2 "Assembly language instruction list"
+.PP
 For each instruction in the list the range of argument values
 in the assembly language is given.
 The column headed \fIassem\fP contains the mnemonics defined
@@ -558,7 +557,7 @@ are indicated by letters:
 .ds z \fBz\fP
 .ds o \fBo\fP
 .ds - \fB\-\fP
-.N 1
+.sp
 .TS
 tab(:);
 c s l l
@@ -579,8 +578,8 @@ l l 15 l l.
 \&\*b:ilb:>= 0:label number
 \&\*r:cst:0,1,2:register number
 \&\*-:::no argument
-.TE 1
-.P
+.TE
+.PP
 The * at the rationale for \*w indicates that the argument
 can either be given as argument or on top of the stack.
 If the argument is omitted, the argument is fetched from the
@@ -589,8 +588,7 @@ it is assumed to be a wordsized unsigned integer.
 Instructions that check for undefined integer or floating-point
 values and underflow or overflow
 are indicated below by (*).
-.N 1
-.VS 0 0
+.sp 1
 .DS
 .ta 12n
 GROUP 1 \- LOAD
@@ -687,7 +685,7 @@ GROUP 7 \- INCREMENT/DECREMENT/ZERO
   ZER \*w :	Load \*w zero bytes
 .DE
 
-.DS				\" ???
+.DS
 GROUP 8 \- CONVERT    (stack:	source, source size, dest. size (top))
 
   CII \*- :	Convert integer to integer (*)
@@ -744,7 +742,7 @@ GROUP 12 \- COMPARE
   TGT \*- :	True if greater, i.e. iff top of stack > 0
 .DE
 
-.DS				\" ???
+.DS
 GROUP 13 \- BRANCH
 
   BRA \*b :	Branch unconditionally to label \*b
@@ -801,5 +799,4 @@ GROUP 15 \- MISCELLANEOUS
   SIM \*- :	Store 16 bit ignore mask
   STR \*r :	Store register (0=LB, 1=SP, 2=HP)
   TRP \*- :	Cause trap to occur (Error number on stack)
-.DE 0
-.VS
+.DE

+ 4 - 6
doc/em/cont.nr

@@ -1,6 +1,4 @@
-.MS T A 0
-.ME
-.BP
-.MS B A 0
-.ME
-.CT
+.de PT
+..
+.bp
+.Ct

+ 34 - 43
doc/em/descr.nr

@@ -1,69 +1,62 @@
-.SN 7
-.BP
-.S1 "DESCRIPTORS"
+.bp
+.P1 "DESCRIPTORS"
+.PP
 Several instructions use descriptors, notably the range check instruction,
 the array instructions, the goto instruction and the case jump instructions.
 Descriptors reside in data space.
 They may be constructed at run time, but
 more often they are fixed and allocated in ROM data.
-.P
+.PP
 All instructions using descriptors, except GTO, have as argument
 the size of the integers in the descriptor.
 All implementations have to allow integers of the size of a
 word in descriptors.
 All integers popped from the stack and used for indexing or comparing
 must have the same size as the integers in the descriptor.
-.S2 "Range check descriptors"
+.P2 "Range check descriptors"
+.PP
 Range check descriptors consist of two integers:
-.IS 2
-.PS 1 4 "" .
-.PT
+.IP 1.
 lower bound	signed
-.PT
+.IP 2.
 upper bound	signed
-.PE
-.IE
+.LP
 The range check instruction checks an integer on the stack against
 these bounds and causes a trap if the value is outside the interval.
 The value itself is neither changed nor removed from the stack.
-.S2 "Array descriptors"
+.P2 "Array descriptors"
+.PP
 Each array descriptor describes a single dimension.
 For multi-dimensional arrays, several array instructions are
 needed to access a single element.
 Array descriptors contain the following three integers:
-.IS 2
-.PS 1 4 "" .
-.PT
+.IP 1.
 lower bound		signed
-.PT
+.IP 2.
 upper bound \- lower bound	unsigned
-.PT
+.IP 3.
 number of bytes per element	unsigned
-.PE
-.IE
+.LP
 The array instructions LAR, SAR and AAR have the pointer to the start
 of the descriptor as operand on the stack.
-.sp
+.LP
 The element A[I] is fetched as follows:
-.IS 2
-.PS 1 4 "" .
-.PT
+.IP 1.
 Stack the address of A  (e.g., using LAE or LAL)
-.PT
+.IP 2.
 Stack the value of I (n-byte integer)
-.PT
+.IP 3.
 Stack the pointer to the descriptor (e.g., using LAE)
-.PT
+.IP 4.
 LAR n (n is the size of the integers in the descriptor and I)
-.PE
-.IE
+.LP
 All array instructions first pop the address of the descriptor
 and the index.
 If the index is not within the bounds specified, a trap occurs.
 If ok, (I~\-~lower bound) is multiplied
 by the number of bytes per element (the third word).  The result is added
 to the address of A and replaces A on the stack.
-.A
+.QQ
 At this point LAR, SAR and AAR diverge.
 AAR is finished.  LAR pops the address and fetches the data
 item,
@@ -71,21 +64,19 @@ the size being specified by the descriptor.
 The usual restrictions for memory access must be obeyed.
 SAR pops the address and stores the
 data item now exposed.
-.S2 "Non-local goto descriptors"
+.P2 "Non-local goto descriptors"
+.PP
 The GTO instruction provides a way of returning directly to any
 active procedure invocation.
 The argument of the instruction is the address of a descriptor
 containing three pointers:
-.IS 2
-.PS 1 4 "" .
-.PT
+.IP 1.
 value of PC after the jump
-.PT
+.IP 2.
 value of SP after the jump
-.PT
+.IP 3.
 value of LB after the jump
-.PE
-.IE
+.LP
 GTO replaces the loads PC, SP and LB from the descriptor,
 thereby jumping to a procedure
 and removing zero or more frames from the stack.
@@ -94,7 +85,8 @@ dynamically enclosing procedure,
 because some EM implementations will need to backtrack through
 the dynamic chain and use the implementation dependent data
 in frames to restore registers etc.
-.S2 "Case descriptors"
+.P2 "Case descriptors"
+.PP
 The case jump instructions CSA and CSB both
 provide multiway branches selected by a case index.
 Both fetch two operands from the stack:
@@ -106,7 +98,7 @@ Therefore, the descriptors for CSA and CSB,
 as shown in figure 4, are different.
 All pointers in the table must be addresses of instructions in the
 procedure executing the case instruction.
-.P
+.PP
 CSA selects the new PC by indexing.
 If the index, a signed integer, is greater than or equal to
 the lower bound and less than or equal to the upper bound,
@@ -116,23 +108,22 @@ The table does not contain the value of the upper bound,
 but the value of upper-lower as an unsigned integer.
 The default instruction pointer is used when the index is out of bounds.
 If the resulting PC is 0, then trap.
-.P
+.PP
 CSB selects the new PC by searching.
 The table is searched for an entry with index value equal to the case index.
 That entry or, if none is found, the default entry contains the
 new PC.
 When the resulting PC is 0, a trap is performed.
-.P
+.PP
 The choice of which case instruction to use for
 each source language case statement
 is up to the front end.
 If the range of the index value is dense, i.e
 .DS
 (highest value \- lowest value) / number of cases
-.DE 1
+.DE
 is less than some threshold, then CSA is the obvious choice.
 If the range is sparse, CSB is better.
-.N 2
 .Dr 30
    |--------------------|        |--------------------|  high address
    | pointer for upb    |        |    pointer n-1     |

+ 42 - 43
doc/em/dspace.nr

@@ -1,6 +1,6 @@
-.BP
-.SN 4
-.S1 "DATA ADDRESS SPACE"
+.bp
+.P1 "DATA ADDRESS SPACE"
+.PP
 The data address space is divided into three parts, called 'areas',
 each with its own addressing method:
 global data area,
@@ -9,24 +9,24 @@ and heap data area.
 These data areas must be part of the same
 address space because all data is accessed by
 the same type of pointers.
-.P
+.PP
 Space for global data is reserved using several pseudoinstructions in the
 assembly language, as described in
 the next paragraph and chapter 11.
 The size of the global data area is fixed per program.
-.A
+.QQ
 Global data is addressed absolutely in the machine language.
 Many instructions are available to address global data.
 They all have an absolute address as argument.
 Examples are LOE, LAE and STE.
-.P
+.PP
 Part of the global data area is initialized by the
 compiler, the
 rest is not initialized at all or is initialized
 with a value, typically \-32768 or 0.
 Part of the initialized global data may be made read-only
 if the implementation supports protection.
-.P
+.PP
 The local data area is used as a stack,
 which grows from high to low addresses
 and contains some data for each active procedure
@@ -44,14 +44,14 @@ Variables in other active procedures are addressed by following
 the chain of statically enclosing procedures using the LXL or LXA instruction.
 The variables in dynamically enclosing procedures can be
 addressed with the use of the DCH instruction.
-.A
+.QQ
 Many instructions have offsets to LB as argument,
 for instance LOL, LAL and STL.
 The arguments of these instructions range from \-1 to some
 (negative) minimum
 for the access of local storage and from 0 to some (positive)
 maximum for parameter access.
-.P
+.PP
 The procedure call instructions CAL and CAI each create a new frame
 on the stack.
 Each procedure has an assembly-time parameter specifying
@@ -62,7 +62,7 @@ Each procedure, therefore, starts with a stack with the local variables
 already allocated.
 The return instructions RET and RTT remove a frame.
 The actual parameters must be removed by the calling procedure.
-.P
+.PP
 RET may copy some words from the stack of
 the returning procedure to an unnamed 'function return area'.
 This area is available for 'READ-ONCE' access using the LFR instruction.
@@ -86,7 +86,7 @@ area is twice the pointer size,
 because we want to be able to handle 'procedure instance
 identifiers' which consist of a procedure identifier and the LB
 of a frame belonging to that procedure.
-.P
+.PP
 The heap data area grows upwards, to higher numbered
 addresses.
 It is initially empty.
@@ -96,7 +96,8 @@ The heap pointer may be manipulated
 by the LOR and STR instructions.
 The heap can only be addressed indirectly,
 by pointers derived from previous values of HP.
-.S2 "Global data area"
+.P2 "Global data area"
+.PP
 The initial size of the global data area is determined at assembly time.
 Global data is allocated by several
 pseudoinstructions in the EM assembly
@@ -109,7 +110,7 @@ under certain conditions, several blocks are allocated
 in a single fragment.
 This guarantees that the bytes of these blocks
 are consecutive.
-.P
+.PP
 Global data is addressed absolutely in binary
 machine language.
 Most compilers, however,
@@ -124,7 +125,7 @@ It is the task of the assembler/loader to
 translate these labels into absolute addresses.
 These labels may also be used
 in CON and ROM pseudoinstructions to initialize pointers.
-.P
+.PP
 The pseudoinstruction CON allocates initialized data.
 ROM acts like CON but indicates that the initialized data will
 not change during execution of the program.
@@ -134,7 +135,7 @@ data.
 The pseudoinstruction HOL is similar to BSS,
 but it alters the meaning of subsequent absolute addressing in
 the assembly language.
-.P
+.PP
 Another type of global data is a small block,
 called the ABS block, with an implementation defined size.
 Storage in this type of block can only be addressed
@@ -146,7 +147,7 @@ update this counter.
 A pointer at location 4 points to a string containing the
 current source file name.
 The instruction FIL can be used to update the pointer.
-.P
+.PP
 All numeric arguments of the instructions that address
 the global data area refer to locations in the
 ABS block unless
@@ -158,7 +159,7 @@ Thus LOE 0 loads the zeroth word of the most recent HOL, unless no HOL has
 appeared in the current file so
 far, in which case it loads the zeroth word of the
 ABS fragment.
-.P
+.PP
 The global data area is highly fragmented.
 The ABS block and each HOL and BSS block are separate fragments.
 The way fragments are formed from CON and ROM blocks is more complex.
@@ -169,12 +170,11 @@ allocated consecutively in a single fragment, unless
 these CON pseudos are separated in the assembly language program
 by a data label definition or one or more of the following pseudos:
 .DS
-
-     ROM, BSS, HOL and END
-
+ROM, BSS, HOL and END
 .DE
 An analogous rule holds for ROM pseudos.
-.S2 "Local data area"
+.P2 "Local data area"
+.PP
 The local data area consists of a sequence of frames, one for
 each active procedure.
 Below the frame of the current procedure resides the
@@ -183,17 +183,15 @@ Frames are generated by procedure calls and are
 removed by procedure returns.
 A procedure frame consists of six 'zones':
 .DS
-
-  1.  The return status block
-  2.  The local variables and compiler temporaries
-  3.  The register save block
-  4.  The dynamic local generators
-  5.  The operand stack.
-  6.  The parameters of a procedure one level deeper
-
+1.  The return status block
+2.  The local variables and compiler temporaries
+3.  The register save block
+4.  The dynamic local generators
+5.  The operand stack.
+6.  The parameters of a procedure one level deeper
 .DE
 A sample frame is shown in Figure 1.
-.P
+.PP
 Before a procedure call is performed the actual
 parameters are pushed onto the stack of the calling procedure.
 The exact details are compiler dependent.
@@ -216,11 +214,11 @@ These instructions assume that this parameter contains the LB of
 the statically enclosing procedure.
 Procedures that do not have a dynamically enclosing procedure
 do not need a static link at offset 0.
-.P
+.PP
 Two instructions are available to perform procedure calls, CAL
 and CAI.
 Several tasks are performed by these call instructions.
-.A
+.QQ
 First, a part of the status of the calling procedure is
 saved on the stack in the return status block.
 This block should contain the return address of the calling
@@ -235,12 +233,12 @@ The stack frames need not be contiguous then and the first
 status save area can contain the parameter base AB,
 which has the value of SP just after the last parameter has
 been pushed.
-.A
+.QQ
 Second, the LB is changed to point to the
 first word above the local variables.
 The new LB is a copy of the SP after the return status
 block has been pushed.
-.A
+.QQ
 Third, the amount of local storage needed by the procedure is
 reserved.
 The parameters and local storage are accessed by the same instructions.
@@ -256,28 +254,28 @@ The initial value of the allocated words is
 not defined, but implementations that check for undefined
 values will probably initialize them with a
 special 'undefined' pattern, typically \-32768.
-.A
+.QQ
 Fourth, any EM implementation is allowed to reserve a variable size
 block beneath the local variables.
 This block could, for example, be used to save a variable number
 of registers.
-.A
+.QQ
 Finally, the address of the entry point of the called procedure
 is loaded into the Program Counter.
-.P
+.PP
 The ASP instruction can be used to allocate further (dynamic)
 local storage.
 The base address of such storage must be obtained with a LOR~SP
 instruction.
 This same instruction ASP may also be used
 to remove some words from the stack.
-.P
+.PP
 There is a version of ASP, called ASS, which fetches the number
 of bytes to allocate from the stack.
 It can be used to allocate space for local
 objects whose size is unknown at compile time,
 so called 'dynamic local generators'.
-.P
+.PP
 Control is returned to the calling procedure with a RET instruction.
 Any return value is then copied to the 'function return area'.
 The frame created by the call is deallocated and the status of
@@ -293,7 +291,7 @@ Violating this restriction might result in hard to detect
 errors.
 The calling procedure has to remove the parameters from the stack.
 This can be done with the aforementioned ASP instruction.
-.P
+.PP
 Each procedure frame is a separate fragment.
 Because any fragment may be placed anywhere in memory,
 procedure frames need not be contiguous.
@@ -345,7 +343,8 @@ procedure frames need not be contiguous.
 .Df
 Figure 1. A sample procedure frame and parameters.
 .De
-.S2 "Heap data area"
+.P2 "Heap data area"
+.PP
 The heap area starts empty, with HP
 pointing to the low end of it.
 HP always contains a word address.
@@ -360,7 +359,7 @@ are allocated to the heap.
 The heap may not grow into a part of memory that is already allocated.
 When this is attempted, the STR instruction will cause a trap to occur.
 In this case, HP retains its old value.
-.P
+.PP
 The only way to address the heap is indirectly.
 Whenever an object is allocated by increasing HP,
 then the old HP value must be saved and can be used later to address
@@ -370,7 +369,7 @@ is no longer part of the heap, then an attempt to access
 the object is not allowed.
 Furthermore, if the heap pointer is increased again to above
 the object address, then access to the old object gives undefined results.
-.P
+.PP
 The heap is a single fragment.
 All bytes have consecutive addresses.
 No limits are imposed on the size of the heap as long as it fits

+ 10 - 0
doc/em/em.i

@@ -1,3 +1,10 @@
+.bp
+.AP "EM INTERPRETER"
+.nf
+.ft CW
+.lg 0
+.nr x \w'        '
+.ta \nxu +\nxu +\nxu +\nxu +\nxu +\nxu +\nxu +\nxu +\nxu +\nxu
 
 { This  is an interpreter for EM.  It serves as  the official machine
   definition.  This interpreter must run on a machine which supports
@@ -1666,3 +1673,6 @@ case insr of
   writeln('halt with exit status: ',exitstatus:1);
   doident;
 end.
+.ft P
+.lg 1
+.fi

+ 47 - 66
doc/em/env.nr

@@ -1,56 +1,43 @@
-.SN 8
-.VS 1 0
-.BP
-.S1 "ENVIRONMENT INTERACTIONS"
+.bp
+.P1 "ENVIRONMENT INTERACTIONS"
+.PP
 EM programs can interact with their environment in three ways.
 Two, starting/stopping and monitor calls, are dealt with in this chapter.
 The remaining way to interact, interrupts, will be treated
 together with traps in chapter 9.
-.S2 "Program starting and stopping"
+.P2 "Program starting and stopping"
+.PP
 EM user programs start with a call to a procedure called
 _m_a_i_n.
 The assembler and backends look for the definition of a procedure
 with this name in their input.
 The call passes three parameters to the procedure.
 The parameters are similar to the parameters supplied by the
-UNIX
-.FS
-UNIX is a Trademark of Bell Laboratories.
-.FE
+.UX
 operating system to C programs.
-These parameters are often called
-.BW argc ,
-.B argv
-and
-.BW envp .
+These parameters are often called \fBargc\fP, \fBargv\fP and \fBenvp\fP.
 Argc is the parameter nearest to LB and is a wordsized integer.
 The other two are pointers to the first element of an array of
 string pointers.
-.N
-The
-.B argv
-array contains
-.B argc
+The \fBargv\fP array contains \fBargc\fP
 strings, the first of which contains the program call name.
-The other strings in the
-.B argv
+The other strings in the \fBargv\fP
 array are the program parameters.
-.P
-The
-.B envp
+.PP
+The \fBenvp\fP
 array contains strings in the form "name=string", where 'name'
 is the name of an environment variable and string its value.
-The
-.B envp
+The \fBenvp\fP
 is terminated by a zero pointer.
-.P
+.PP
 An EM user program stops if the program returns from the first
 invocation of _m_a_i_n.
 The contents of the function return area are used to procure a
 wordsized program return code.
 EM programs also stop when traps and interrupts occur that are
 not caught and when the exit monitor call is executed.
-.S2 "Input/Output and other monitor calls"
+.P2 "Input/Output and other monitor calls"
+.PP
 EM differs from most conventional machines in that it has high level i/o
 instructions.
 Typical instructions are OPEN FILE and READ FROM FILE instead
@@ -58,7 +45,7 @@ of low level instructions such as setting and clearing
 bits in device registers.
 By providing such high level i/o primitives, the task of implementing
 EM on various non EM machines is made considerably easier.
-.P
+.PP
 I/O is initiated by the MON instruction, which expects an iocode on top
 of the stack.
 Often there are also parameters which are pushed on the
@@ -68,45 +55,35 @@ Some i/o functions also provide results, which are returned on the stack.
 In the list of monitor calls we use several types of parameters and results,
 these types consist of integers and unsigneds of varying sizes, but never
 smaller than the wordsize, and the two pointer types.
-.N 1
+.LP
 The names of the types used are:
-.IS 4
-.PS - 10
-.PT int
-an integer of wordsize
-.PT int2
-an integer whose size is the maximum of the wordsize and 2
-bytes
-.PT int4
-an integer whose size is the maximum of the wordsize and 4
-bytes
-.PT intp
-an integer with the size of a pointer
-.PT uns2
-an unsigned integer whose size is the maximum of the wordsize and 2
-.PT unsp
-an unsigned integer with the size of a pointer
-.PT ptr
-a pointer into data space
-.PE 1
-.IE 0
+.DS
+.TS
+tab(:);
+l l.
+int:an integer of wordsize
+int2:an integer whose size is the maximum of the wordsize and 2 bytes
+int4:an integer whose size is the maximum of the wordsize and 4 bytes
+intp:an integer with the size of a pointer
+uns2:an unsigned integer whose size is the maximum of the wordsize and 2
+unsp:an unsigned integer with the size of a pointer
+ptr:a pointer into data space
+.TE
+.DE
+.LP
 The table below lists the i/o codes with their results and
 parameters.
 This list is similar to the system calls of the UNIX Version 7
 operating system.
-.A
+.QQ
 To execute a monitor call, proceed as follows:
-.IS 2
-.N 1
-.PS a 4 "" )
-.PT
+.IP a)
 Stack the parameters, in reverse order, last parameter first.
-.PT
+.IP b)
 Push the monitor call number (iocode) onto the stack.
-.PT
+.IP c)
 Execute the MON instruction.
-.PE 1
-.IE
+.LP
 An error code is present on the top of the stack after
 execution of most monitor calls.
 If this error code is zero, the call performed the action
@@ -117,9 +94,12 @@ This construction enables programs to test for failure with a
 single instruction (~TEQ or TNE~) and still find out the cause of
 the failure.
 The result name 'e' is reserved for the error code.
-.N 1
+.ne 5
+.LP
 List of monitor calls.
-.DS B
+.LP
+.nf
+.na
 .ta 4n 13n 29n 52n
 nr	name	parameters	results	function
 
@@ -191,22 +171,23 @@ nr	name	parameters	results	function
 			e:int	Execute a file
 60	Umask	mask:int2	oldmask:int2	Set file creation mode mask
 61	Chroot	string:ptr	e:int	Change root directory
-.DE 1
+.fi
+.ad
+.LP
 Codes 0, 11, 13, 17, 31, 32, 38, 39, 40, 45, 49, 50, 52,
 55, 57, 58, 62, and 63 are
 not used.
-.P
+.PP
 All monitor calls, except fork and sigtrp
 are the same as the UNIX version 7 system calls.
-.P
+.PP
 The sigtrp entry maps UNIX signals onto EM interrupts.
 Normally, trapno is in the range 0 to 252.
 In that case it requests that signal signo
 will cause trap trapno to occur.
 When given trap number \-2, default signal handling is reset, and when given
 trap number \-3, the signal is ignored.
-.P
+.PP
 The flag returned by fork is 1 in the child process and 0 in
 the parent.
 The pid returned is the process-id of the other process.
-.VS

+ 25 - 34
doc/em/intro.nr

@@ -1,48 +1,42 @@
-.BP
-.S1 "INTRODUCTION"
+.bp
+.P1 "INTRODUCTION"
+.PP
 EM is a family of intermediate languages designed for producing
 portable compilers.
-The general strategy is for a program called
-.B front end
+The general strategy is for a program called \fBfront end\fP
 to translate the source program to EM.
-Another program,
-.B back
-.BW end
+Another program, \fBback end\fP,
 translates EM to target assembly language.
 Alternatively, the EM code can be assembled to a binary form
 and interpreted.
 These considerations led to the following goals:
-.IS 2 10
-.PS 1 4
-.PT
+.IP 1
 The design should allow translation to,
 or interpretation on, a wide range of existing machines.
 Design decisions should be delayed as far as possible
 and the implications of these decisions should
 be localized as much as possible.
-.N
+.br
 The current microcomputer technology offers 8, 16 and 32 bit machines
 with various sizes of address space.
 EM should be flexible enough to be useful on most of these
 machines.
 The differences between the members of the EM family should only
 concern the wordsize and address space size.
-.PT
+.IP 2
 The architecture should ease the task of code generation for
 high level languages such as Pascal, C, Ada, Algol 68, BCPL.
-.PT
+.IP 3
 The instruction set used by the interpreter should be compact,
 to reduce the amount of memory needed
 for program storage, and to reduce the time needed to transmit
 programs over communication lines.
-.PT
+.IP 3
 It should be designed with microprogrammed implementations in
 mind; in particular, the use of many short fields within
 instruction opcodes should be avoided, because their extraction by the
 microprogram or conversion to other instruction formats is inefficient.
-.PE
-.IE
-.A
+.PP
 The basic architecture is based on the concept of a stack. The stack
 is used for procedure return addresses, actual parameters, local variables,
 and arithmetic operations.
@@ -61,7 +55,7 @@ stack.
 For all types except pointers,
 these instructions have the object size
 as argument.
-.P
+.PP
 There are no visible general registers used for arithmetic operands
 etc. This is in contrast to most third generation computers, which usually
 have 8 or 16 general registers. The decision not to have a group of
@@ -69,11 +63,11 @@ general registers was fully intentional, and follows W.L. Van der
 Poel's dictum that a machine should have 0, 1, or an infinite
 number of any feature. General registers have two primary uses: to hold
 intermediate results of complicated expressions, e.g.
-.IS 5 0 1
+.DS
 ((a*b + c*d)/e + f*g/h) * i
-.IE 1
+.DE
 and to hold local variables.
-.P
+.PP
 Various studies
 have shown that the average expression has fewer than two operands,
 making the former use of registers of doubtful value. The present trend
@@ -81,11 +75,9 @@ toward structured programs consisting of many small
 procedures greatly reduces the value of registers to hold local variables
 because the large number of procedure calls implies a large overhead in
 saving and restoring the registers at every call.
-.P
+.PP
 Although there are no general purpose registers, there are a
 few internal registers with specific functions as follows:
-.IS 2
-.N 1
 .TS
 tab(:);
 l 1 l l l.
@@ -94,9 +86,8 @@ LB:\-:Local Base:Points to base of the local variables
 :::in the current procedure.
 SP:\-:Stack Pointer:Points to the highest occupied word on the stack.
 HP:\-:Heap Pointer:Points to the top of the heap area.
-.TE 1
-.IE
-.A
+.TE
+.PP
 Furthermore, reverse Polish code is much easier to generate than
 multi-register machine code, especially if highly efficient code is
 desired.
@@ -106,7 +97,7 @@ An EM machine can
 achieve high performance by keeping part of the stack
 in high speed storage (a cache or microprogram scratchpad memory) rather
 than in primary memory.
-.P
+.PP
 Again according to van der Poel's dictum,
 all EM instructions have zero or one argument.
 We believe that instructions needing two arguments
@@ -116,11 +107,11 @@ circumstances as well.
 Moreover, these two instructions together often
 have a shorter encoding than the single
 instruction before.
-.P
+.PP
 This document describes EM at three different levels:
 the abstract level, the assembly language level and
 the machine language level.
-.A
+.QQ
 The most important level is that of the abstract EM architecture.
 This level deals with the basic design issues.
 Only the functional capabilities of instructions are relevant, not their
@@ -128,14 +119,14 @@ format or encoding.
 Most chapters of this document refer to the abstract level
 and it is explicitly stated whenever
 another level is described.
-.A
+.QQ
 The assembly language is intended for the compiler writer.
 It presents a more or less orthogonal instruction
 set and provides symbolic names for data.
 Moreover, it facilitates the linking of
 separately compiled 'modules' into a single program
 by providing several pseudoinstructions.
-.A
+.QQ
 The machine language is designed for interpretation with a compact
 program text and easy decoding.
 The binary representation of the machine language instruction set is
@@ -144,7 +135,7 @@ Frequent instructions have a short opcode.
 The encoding is fully byte oriented.
 These bytes do not contain small bit fields, because
 bit fields would slow down decoding considerably.
-.P
+.PP
 A common use for EM is for producing portable (cross) compilers.
 When used this way, the compilers produce
 EM assembly language as their output.
@@ -156,7 +147,7 @@ machine language instructions is irrelevant.
 On the other hand, when writing an interpreter for EM machine language
 programs, the interpreter must deal with the machine language
 and not with the symbolic assembly language.
-.P
+.PP
 As mentioned above, the
 current microcomputer technology offers 8, 16 and 32 bit
 machines with address spaces ranging from

+ 11 - 16
doc/em/ispace.nr

@@ -1,6 +1,5 @@
-.SN 3
-.BP
-.S1 "INSTRUCTION ADDRESS SPACE"
+.bp
+.P1 "INSTRUCTION ADDRESS SPACE"
 The instruction space of the EM machine contains
 the code for procedures.
 Tables necessary for the execution of this code, for example, procedure
@@ -10,14 +9,14 @@ the execution of a program, so that it may be
 protected.
 No further restrictions to the instruction address space are
 necessary for the abstract and assembly language level.
-.P
+.PP
 Each procedure has a single entry point: the first instruction.
 A special type of pointer identifies a procedure.
 Pointers into the instruction
 address space have the same size as pointers into data space and
 can, for example, contain the address of the first instruction
 or an index in a procedure descriptor table.
-.A
+.QQ
 There is a single EM program counter, PC, pointing
 to the next instruction to be executed.
 The procedure pointed to by PC is
@@ -28,35 +27,31 @@ The calling procedure remains 'active' and is resumed whenever the called
 procedure returns.
 Note that a procedure has several 'active' invocations when
 called recursively.
-.P
+.PP
 Each procedure must return properly.
 It is not allowed to fall through to the
 code of the next procedure.
 There are several ways to exit from a procedure:
-.IS 3
-.PS
-.PT
+.IP -
 the RET instruction, which returns to the
 calling procedure.
-.PT
+.IP -
 the RTT instruction, which exits a trap handling routine and resumes
 the trapping instruction (see next chapter).
-.PT
+.IP -
 the GTO instruction, which is used for non-local goto's.
 It can remove several frames from the stack and transfer
 control to an active procedure.
 (see also MES~11 in paragraph 11.1.4.4)
-.PE
-.IE
-.P
+.PP
 All branch instructions can transfer control
 to any label within the same procedure.
 Branch instructions can never jump out of a procedure.
-.P
+.PP
 Several language implementations use a so called procedure
 instance identifier, a combination of a procedure identifier and
 the LB of a stack frame, also called static link.
-.P
+.PP
 The program text for each procedure, as well as any tables,
 are fragments and can be allocated anywhere
 in the instruction address space.

+ 68 - 88
doc/em/mach.nr

@@ -1,6 +1,6 @@
-.BP
-.SN 10
-.S1 "EM MACHINE LANGUAGE"
+.bp
+.P1 "EM MACHINE LANGUAGE"
+.PP
 The EM machine language is designed to make program text compact
 and to make decoding easy.
 Compact program text has many advantages: programs execute faster,
@@ -11,16 +11,18 @@ that it is feasible to use interpreters as long as EM hardware
 machines are not available.
 This chapter is irrelevant when back ends are used to
 produce executable target machine code.
-.S2 "Instruction encoding"
+.P2 "Instruction encoding"
+.PP
 A design goal of EM is to make the
 program text as compact as possible.
 Decoding must be easy, however.
 The encoding is fully byte oriented, without any small bit fields.
 There are 256 primary opcodes, two of which are an escape to
 two groups of 256 secondary opcodes each.
-.A
+.QQ
 EM instructions without arguments have a single opcode assigned,
 possibly escaped:
+.ta 12n 24n
 .Dr 6
          |--------------|
          |    opcode    |
@@ -37,7 +39,7 @@ Several instructions have an address from the global data area
 as argument.
 Other instructions have different opcodes for positive
 and negative arguments.
-.N 1
+.LP
 There is always an opcode that takes the next two bytes as argument,
 high byte first:
 .Dr 6
@@ -94,7 +96,7 @@ several different encodings are available.
 It is the task of the assembler to select the shortest of these.
 The savings by these mini and shortie
 opcodes are considerable, about 55%.
-.P
+.PP
 Further improvements are possible:
 the arguments of
 many instructions are a multiple of the wordsize.
@@ -106,26 +108,24 @@ The arguments of some other instructions
 rarely or never assume the value 0, but start at 1.
 The value 1 is then encoded as 0,
 2 as 1 and so on.
-.P
+.PP
 Assigning opcodes to instructions by the assembler is completely
 table driven.
 For details see appendix B.
-.S2 "Procedure descriptors"
+.P2 "Procedure descriptors"
+.PP
 The procedure identifiers used in the interpreter are indices
 into a table of procedure descriptors.
 Each descriptor contains:
-.IS 6
-.PS - 4
-.PT 1.
+.IP 1.
 the number of bytes to be reserved for locals at each
 invocation.
-.N
+.br
 This is a pointer-sized integer.
-.PT 2.
+.IP 2.
 the start address of the procedure
-.PE
-.IE
-.S2 "Load format"
+.P2 "Load format"
+.PP
 The EM machine language load format defines the interface between
 the EM assembler/loader and the EM machine itself.
 A load file consists of a header, the program text to be executed,
@@ -133,7 +133,7 @@ a description of the global data area and the procedure descriptor table,
 in this order.
 All integers in the load file are presented with the
 least significant byte first.
-.P
+.PP
 The header has two parts: the first half (eight 16-bit integers)
 aids in selecting
 the correct EM machine or interpreter.
@@ -141,68 +141,59 @@ Some EM machines, for instance, may have hardware floating point
 instructions.
 .N
 The header entries are as follows (bit 0 is rightmost):
-.IS 2
-.VS 1 0
-.PS 1 4 "" :
-.PT
+.IP 1:
 magic number (07255)
-.PT
+.IP 2:
 flag bits with the following meaning:
-.PS - 7 "" :
-.PT bit 0
+.RS
+.IP "bit 0"
 TEST; test for integer overflow etc.
-.PT bit 1
+.IP "bit 1"
 PROFILE; for each source line: count the number of memory
 cycles executed.
-.PT bit 2
+.IP "bit 2"
 FLOW; for each source line: set a bit in a bit map table if
 instructions on that line are executed.
-.PT bit 3
+.IP "bit 3"
 COUNT; for each source line: increment a counter if that line
 is entered.
-.PT bit 4
+.IP "bit 4"
 REALS; set if a program uses floating point instructions.
-.PT bit 5
+.IP "bit 5"
 EXTRA; more tests during compiler debugging.
-.PE
-.PT
+.RE
+.IP 3:
 number of unresolved references.
-.PT
+.IP 4:
 version number; used to detect obsolete EM load files.
-.PT
+.IP 5:
 wordsize ; the number of bytes in each machine word.
-.PT
+.IP 6:
 pointer size ; the number of bytes available for addressing.
-.PT
+.IP 7:
 unused
-.PT
+.IP 8:
 unused
-.PE
-.IE
+.LP
 The second part of the header (eight entries, of pointer size bytes each)
 describes the load file itself:
-.IS 2
-.PS 1 4 "" :
-.PT
+.IP 1:
 NTEXT; the program text size in bytes.
-.PT
+.IP 2:
 NDATA; the number of load-file descriptors (see below).
-.PT
+.IP 3:
 NPROC; the number of entries in the procedure descriptor table.
-.PT
+.IP 4:
 ENTRY; procedure number of the procedure to start with.
-.PT
+.IP 5:
 NLINE; the maximum source line number.
-.PT
+.IP 6:
 SZDATA; the address of the lowest uninitialized data byte.
-.PT
+.IP 7:
 unused
-.PT
+.IP 8:
 unused
-.PE
-.IE
-.VS
-.P
+.PP
 The program text consists of NTEXT bytes.
 NTEXT is always a multiple of the wordsize.
 The first byte of the program text is the
@@ -212,7 +203,7 @@ Pointers into the program text are found in the procedure descriptor
 table where relocation is simple and in the global data area.
 The initialization of the global data area allows easy
 relocation of pointers into both address spaces.
-.P
+.PP
 The global data area is described by the NDATA descriptors.
 Each descriptor describes a number of consecutive words (of~wordsize)
 and consists of a sequence of bytes.
@@ -220,7 +211,7 @@ While reading the descriptors from the load file, one can
 initialize the global data area from low to high addresses.
 The size of the initialized data area is given by SZDATA,
 this number can be used to check the initialization.
-.N
+.br
 The header of each descriptor consists of a byte, describing the type,
 and a count.
 The number of bytes used for this (unsigned) count depends on the
@@ -232,31 +223,22 @@ At load time an interpreter can
 perform any conversion deemed necessary, such as
 reordering bytes in integers
 and pointers and adding base addresses to pointers.
-.A
+.QQ
 In the following pictures we show a graphical notation of the
 initializers.
 The leftmost rectangle represents the leading byte.
-.N 1
-.VS 1 0
-.DS
-.PS - 4 " "
+.LP
 Fields marked with
-.N 1
-.PT n
-contain a pointer-sized integer used as a count
-.PT m
-contain a one-byte integer used as a count
-.PT b
-contain a one-byte integer
-.PT w
-contain a wordsized integer
-.PT p
-contain a data or instruction pointer
-.PT s
-contain a null terminated ASCII string
-.PE 1
-.DE 0
-.VS
+.TS
+tab(:);
+l l.
+n:contain a pointer-sized integer used as a count
+m:contain a one-byte integer used as a count
+b:contain a one-byte integer
+w:contain a wordsized integer
+p:contain a data or instruction pointer
+s:contain a null terminated ASCII string
+.TE
 .Dr 6
     -------------------
     | 0 |      n      |           repeat last initialization n times
@@ -316,8 +298,7 @@ contain a null terminated ASCII string
     | 8 | m |        s      |     initialized float of size m
     -------------------------
 .De
-.PS - 8
-.PT type~0:
+.IP type~0: 10
 If the last initialization initialized k bytes starting
 at address \fIa\fP, do the same initialization again n times,
 starting at \fIa\fP+k, \fIa\fP+2*k, .... \fIa\fP+n*k.
@@ -328,43 +309,43 @@ pointer,
 in all other descriptors the first byte is followed by a one-byte count.
 This descriptor must be preceded by a descriptor of
 another type.
-.PT type~1:
+.IP type~1: 10
 Reserve m words, not explicitly initialized (BSS and HOL).
-.PT type~2:
+.IP type~2: 10
 The m bytes following the descriptor header are
 initializers for the next m bytes of the
 global data area.
 m is divisible by the wordsize.
-.PT type~3:
+.IP type~3: 10
 The m words following the header are initializers for the next m words of the
 global data area.
-.PT type~4:
+.IP type~4: 10
 The m data address space pointers following the header are
 initializers for the next
 m data pointers in the global data area.
 Interpreters that represent EM pointers by
 target machine addresses must relocate all data pointers.
-.PT type~5:
+.IP type~5: 10
 The m instruction address space pointers following the header are
 initializers for the next
 m instruction pointers in the global data area.
 Interpreters that represent EM instruction pointers by
 target machine addresses must relocate these pointers.
-.PT type~6:
+.IP type~6: 10
 The m bytes following the header form
 a signed integer number with a size of m bytes,
 which is an initializer for the next m bytes
 of the global data area.
 m is governed by the same restrictions as for
 transfer of objects to/from memory.
-.PT type~7:
+.IP type~7: 10
 The m bytes following the header form
 an unsigned integer number with a size of m bytes,
 which is an initializer for the next m bytes
 of the global data area.
 m is governed by the same restrictions as for
 transfer of objects to/from memory.
-.PT type~8:
+.IP type~8: 10
 The header is followed by an ASCII string, null terminated, to
 initialize, in global data,
 a floating point number with a size of m bytes.
@@ -372,8 +353,7 @@ m is governed by the same restrictions as for
 transfer of objects to/from memory.
 The ASCII string contains the notation of a real as used in the
 Pascal language.
-.PE
-.P
+.PP
 The NPROC procedure descriptors on the load file consist of
 an instruction space address (of~pointer~size) and
 an integer (of~pointer~size) specifying the number of bytes for

+ 97 - 23
doc/em/macr.nr

@@ -1,39 +1,113 @@
-.SS 10
-.if n .LL 78
-.RP
-.MS T E
-\!.TL '%'''
-.ME
-.MS T O
-\!.TL '''%'
-.ME
-.MS B
-.sp 1
-.ME
-.SM S1 B
-.SM S2 B
+.LP
+.if n \{\
+.nr LL 78
+.ll 78 \}
+.tr ~ 
 .\" below are three simple macros to get the drawings right
 .\" added by Dick Grune
 .de Dr				\" Drawing $1 (size)
-.N 1
-.NE \\$1
-.NA
+.sp 1
+.ne \\$1
+.na
 .ft CW				\" constant spacing
 .lg 0				\" no ligatures
 ..
 .de Df				\" Drawing Footer
-.N 1
+.br
+.sp 1
 .ft R
-.CS
+.ce 1000
 .lg 1
 ..
 .de De				\" Drawing End $1 (lines)
-.Df				\" if it hasn't happened yet
-.CE
-.AD
-.N \\$1
+.br
+.ft R
+.lg 1
+.ce 0
+.ad
+.sp \\$1
 ..
 .\" macro for exponents, added by Ceriel Jacobs
 .de Ex				\" Exponent $1 $2 [$3]
 \\$1\v'-0.5m'\s-2\\$2\s+2\v'0.5m'\\$3
 ..
+.\" QQ is like PP, but without space
+.				\" use .PP, with PD 0.
+.de QQ
+.nr xx \\n(PD
+.nr PD 0
+.PP
+.nr PD \\n(xx
+..
+.nr N1 0
+.nr N2 0
+.nr N3 0
+.nr N4 0
+.nr N5 0
+.nr A5 0
+.af A5 A
+.de P1
+.nr N2 0
+.nr N1 \\n(N1+1
+.ds Tl "\\n(N1. \\$1
+.Ca 0
+.sp
+.LP
+\\fB\\n(N1.  \\$1\\fP
+.sp
+..
+.de P2
+.nr N3 0
+.nr N2 \\n(N2+1
+.ds Tl "\\n(N1.\\n(N2 \\$1
+.ne 5
+.Ca 2
+.sp
+.LP
+\\fB\\n(N1.\\n(N2  \\$1\fP
+..
+.de P3
+.nr N4 0
+.nr N3 \\n(N3+1
+.ds Tl "\\n(N1.\\n(N2.\\n(N3 \\$1
+.Ca 4
+.LP
+\\fI\\n(N1.\\n(N2.\\n(N3  \\$1\fP
+..
+.de P4
+.nr N4 \\n(N4+1
+.ds Tl "\\n(N1.\\n(N2.\\n(N3.\\n(N4 \\$1
+.ne 5
+.Ca 6
+.LP
+\\fI\\n(N1.\\n(N2.\\n(N3.\\n(N4  \\$1\fP
+..
+.de AP
+.nr N5 \\n(N5+1
+.nr A5 \\n(N5
+.ds Tl "\\n(A5. \\$1
+.ne 5
+.Ca 0
+.LP
+\\fB\\n(A5.  \\$1\\fP
+.sp
+..
+.de Ca
+.da Cc
+.if \\$1=0 \!.sp \\\\n(PDu
+\!\l\&\\$1n\ \&\\*(Tl \l\&|\\\\n(LLu-\w\&\ \\n(PN\&u.\&\ \\n(PN
+\!.br
+.da
+..
+.de Ct
+.Cc
+.rm Cc
+..
+.de PT
+.lt \\n(LLu
+.pc %
+.nr PN \\n%-1
+.if \\n(PN%2=1 .tl '''\\n(PN'
+.if (\\n(PN%2=0)&(\\n(PN) .tl '\\n(PN'''
+.lt \\n(.lu
+..

+ 27 - 38
doc/em/mapping.nr

@@ -1,12 +1,12 @@
-.SN 5
-.BP
-.S1 "MAPPING OF EM DATA MEMORY ONTO TARGET MACHINE MEMORY"
+.bp
+.P1 "MAPPING OF EM DATA MEMORY ONTO TARGET MACHINE MEMORY"
+.PP
 The EM architecture is designed to be implemented
 on many existing and future machines.
 EM memory is highly fragmented to make
 adaptation to various memory architectures possible.
 Format and encoding of pointers is explicitly undefined.
-.P
+.PP
 This chapter gives solutions to some of the
 anticipated problems.
 First, we describe a possible memory layout for machines
@@ -53,11 +53,9 @@ The most straightforward layout is shown in figure 2.
 Figure 2.  Memory layout showing typical register
 positions during execution of an EM program.
 .De
-.N 1
+.sp 1
 The base registers for the various memory pieces can be stored
 in target machine registers or memory.
-.IS
-.N 1
 .TS
 tab(;);
 l 1 l l l.
@@ -65,8 +63,8 @@ PB;:;program base;points to the base of the instruction address space.
 EB;:;external base;points to the base of the data address space.
 HB;:;heap base;points to the base of the heap area.
 ML;:;memory limit;marks the high end of the addressable data space.
-.TE 1
-.IE
+.TE
+.LP
 The stack grows from high
 EM addresses to low EM addresses, and the heap the
 other way.
@@ -74,7 +72,7 @@ The memory between SP and HP is not accessible,
 but may be allocated later to the stack or the heap if needed.
 The local data area is allocated starting at the high end of
 memory.
-.P
+.PP
 Because EM address 0 is not mapped onto target
 address 0, a problem arises when pointers are used.
 If a program pushed a constant, say 6, onto the stack,
@@ -86,7 +84,7 @@ This particular problem is solved by explicitly declaring
 the format of a pointer to be undefined,
 so that using a constant as a pointer is completely illegal.
 However, the general problem of mapping pointers still exists.
-.P
+.PP
 There are two possible solutions.
 In the first solution, EM pointers are represented
 in the target machine as true EM addresses,
@@ -100,7 +98,7 @@ facilities, EB can be kept in a target machine register,
 and the relocation can indeed be done on
 every reference to the data address space
 at a modest cost in speed.
-.P
+.PP
 The other solution consists of having EM pointers
 refer to the true target machine address.
 Thus the instruction LAE 6 (Load Address of External 6)
@@ -112,7 +110,7 @@ However, the problem is not completely solved,
 because a front end may have to initialize a pointer
 in CON or ROM data to point to a global address.
 This pointer must also be relocated by the back end or the interpreter.
-.P
+.PP
 Although the EM stack grows from high to low EM addresses,
 some machines have hardware PUSH and POP
 instructions that require the stack to grow upwards.
@@ -144,17 +142,13 @@ Figure 3. Two possible memory implementations.
 Numbers within the boxes are EM addresses.
 The other numbers are physical addresses.
 .De
-.A 1 0
+.LP
 So, we have two different EM memory implementations:
-.IS
-.PS - 4
-.PT A~\-
+.IP "A~\-"
 stack downwards
-.PT B~\-
+.IP "B~\-"
 stack upwards
-.PE
-.IE
-.P
+.PP
 For each of these two possibilities we give the translation of
 the EM instructions to push the third byte of a global data
 block starting at EM address 40 onto the stack and to load the
@@ -164,22 +158,20 @@ The target machine used is a PDP-11 augmented with push and pop instructions.
 Registers 'r0' and 'r1' are used and suffer from sign extension for byte
 transfers.
 Push $40 means push the constant 40, not word 40.
-.P
+.PP
 The translation of the EM instructions depends on the pointer representation
 used.
 For each of the two solutions explained above the translation is given.
-.P
+.PP
 First, the translation for the two implementations using EM addresses as
 pointer representation:
-.DS
+.KS
 .TS
 tab(:), center;
 l s l s l s
-_ s _ s _ s
 l 2 l 6 l 2 l 6 l 2 l.
 EM:type A:type B
-
-
+_
 LAE:40:push:$40:push:$40
 
 ADP:3:pop:r0:pop:r0
@@ -194,20 +186,17 @@ LOI:1:pop:r0:pop:r0
 
 LOE:40:push:eb+40:push:eb-41
 .TE
-.DE
-.P
+.KE
+.PP
 The translation for the two implementations, if the target machine address is
 used as pointer representation, is:
-.N 1
-.DS
+.KS
 .TS
 tab(:), center;
 l s l s l s
-_ s _ s _ s
 l 2 l 6 l 2 l 6 l 2 l.
 EM:type A:type B
-
-
+_
 LAE:40:push:$eb+40:push:$eb-40
 
 ADP:3:pop:r0:pop:r0
@@ -221,12 +210,12 @@ LOI:1:pop:r0:pop:r0
 
 LOE:40:push:eb+40:push:eb-41
 .TE
-.DE
-.P
+.KE
+.PP
 The translation presented above is not intended to be optimal.
 Most machines can handle these simple cases in one or two instructions.
 It demonstrates, however, the flexibility of the EM design.
-.P
+.PP
 There are several possibilities to implement EM on machines with
 address spaces larger than 64k bytes.
 For EM with two byte pointers one could allocate instruction and
@@ -236,7 +225,7 @@ but the base registers PB and EB may be loaded in hardware registers
 wider than 16 bits, if available.
 EM implementations can also make efficient use of a machine
 with separate instruction and data space.
-.P
+.PP
 EM with 32 bit pointers allows one to make use of machines
 with large address spaces.
 In a virtual, segmented memory system one could use a separate

+ 9 - 9
doc/em/mem.nr

@@ -1,13 +1,13 @@
-.BP
-.SN 2
-.S1 MEMORY
+.bp
+.P1 MEMORY
+.PP
 The EM machine has two distinct address spaces,
 one for instructions and one for data.
 The data space is divided up into 8-bit bytes.
 The smallest addressable unit is a byte.
 Bytes are numbered consecutively from 0 to some maximum.
 All sizes in EM are expressed in bytes.
-.P
+.PP
 Some EM instructions can transfer objects containing several bytes
 to and/or from memory.
 The size of all objects larger than a word must be a multiple of
@@ -26,7 +26,7 @@ location \fIm\fP and the wordsize is 2,
 \fIm\fP must be a multiple of 2 and the bytes at
 locations \fIm\fP, \fIm\fP\|+\|1,\fIm\fP\|+\|2 and
 \fIm\fP\|+\|3 are overwritten.
-.P
+.PP
 The size of almost all objects in EM
 is an integral number of words.
 Only two operations are allowed on
@@ -42,11 +42,11 @@ EM provides a way to sign-extend a small integer.
 Popping a small object from the stack removes a word
 from the stack, stores the least significant byte(s)
 of this word in memory and discards the rest of the word.
-.P
+.PP
 The format of pointers into both address spaces is explicitly undefined.
 The size of a pointer, however, is fixed for a member of EM, so that
 the compiler writer knows how much storage to allocate for a pointer.
-.P
+.PP
 A minor problem is raised by the undefined pointer format.
 Some languages, notably Pascal, require a special,
 otherwise illegal, pointer value to represent the nil pointer.
@@ -59,12 +59,12 @@ but it is hard to imagine an implementation
 for which the current solution is inadequate,
 especially because the first word in the EM data space
 is special and probably not the target of any pointer.
-.P
+.PP
 The next two chapters describe the EM memory
 in more detail.
 One describes the instruction address space,
 the other the data address space.
-.P
+.PP
 A design goal of EM has been to allow
 its implementation on a wide range of existing machines,
 as well as allowing a new one to be built in hardware.

+ 3 - 8
doc/em/title.nr

@@ -1,6 +1,4 @@
-.po 0
-.TP 1
-.ll 79n
+.LP
 \&
 .sp 10
 .ce 4
@@ -25,12 +23,9 @@ Abstract
 .ti +5
 EM is a family of intermediate languages
 designed for producing portable compilers.
-A program called
-.B front end
+A program called \fBfront end\fP
 translates source programs to EM.
-Another program,
-.B back
-.BW end ,
+Another program, \fBback end\fP,
 translates EM to the assembly language of the target machine.
 Alternatively, the EM program can be assembled to a highly
 efficient binary format for interpretation.

+ 28 - 30
doc/em/traps.nr

@@ -1,13 +1,12 @@
-.SN 9
-.VS 1 0
-.BP
-.S1 "TRAPS AND INTERRUPTS"
+.bp
+.P1 "TRAPS AND INTERRUPTS"
+.PP
 EM provides a means for the user program to catch all traps
 generated by the program itself, the hardware, or external conditions.
 This mechanism uses five instructions: LIM, SIM, SIG, TRP and RTT.
 This section of the manual may be omitted on the first reading since it
 presupposes knowledge of the EM instruction set.
-.P
+.PP
 The action taken when a trap occurs is determined by the value
 of an internal EM trap register.
 This register contains a pointer to a procedure.
@@ -26,7 +25,7 @@ Two consecutive SIGs are a no-op.
 When a trap occurs, the trap register is reset to its initial
 condition, to prevent recursive traps from hanging the machine up,
 e.g. stack overflow in the stack overflow handling procedure.
-.P
+.PP
 The runtime systems for some languages need to ignore some EM
 traps.
 EM offers a feature called the ignore mask.
@@ -37,24 +36,24 @@ If a certain bit is 1 the corresponding trap never
 occurs and processing simply continues.
 The actions performed by the offending instruction are
 described by the Pascal program in appendix A.
-.N
+.br
 If the bit is 0, traps are not ignored.
 The instructions LIM and SIM allow copying and replacement of
 the ignore mask.~
-.P
+.PP
 The TRP instruction generates a trap, the trap number being found on the
 stack.
 This is, among other things,
 useful for library procedures and runtime systems.
 It can also be used by a low level trap procedure to pass the trap to a
 higher level one (see example below).
-.P
+.PP
 The RTT instruction returns from the trap procedure and continues after the
 trap.
 In the list below all traps marked with an asterisk ('*') are
 considered to be fatal and it is explicitly undefined what happens when
 restarting after the trap.
-.P
+.PP
 The way a trap procedure is called is completely compatible
 with normal calling conventions. The only way a trap procedure
 differs from normal procedures is the return. It has to use RTT instead
@@ -62,25 +61,20 @@ of RET. This is necessary because the complete runtime status is saved on the
 stack before calling the procedure and all this status has to be reloaded.
 Error numbers are in the range 0 to 252.
 The trap numbers are divided into three categories:
-.IS 4
-.N 1
-.PS - 10
-.PT ~~0\-~63
+.IP "\0\00\-\063" 12
 EM machine errors, e.g. illegal instruction.
-.PS - 8
-.PT ~0\-15
+.RS
+.IP "\00\-15" 8
 maskable
-.PT 16\-63
+.IP "16\-63" 8
 not maskable
-.PE
-.PT ~64\-127
+.RE
+.IP "\064\-127" 12
 Reserved for use by compilers, run time systems, etc.
-.PT 128\-252
+.IP "128\-252" 12
 Available for user programs.
-.PE 1
-.IE
+.LP
 EM machine errors are numbered as follows:
-.DS I 5
 .TS
 tab(@);
 n l l.
@@ -108,15 +102,16 @@ n l l.
 26@EBADLIN@Argument of LIN too high
 27@EBADGTO@GTO descriptor error
 .TE
-.DE 0
-.P
+.PP
 As an example,
 suppose a subprocedure has to be written to do a numeric
 calculation.
 When an overflow occurs the computation has to be stopped and
 the higher level procedure must be resumed.
 This can be programmed as follows using the mechanism described above:
-.DS B
+.LP
+.KS
+.nf
 .ta 1n 24n
 	mes 2,2,2	; set sizes
 ersave
@@ -150,10 +145,12 @@ msave
 jmpbuf
 	con *1,0,0
 	end
-.DE 0
-.VS
-.DS
+.KE
+.KS
+.LP
 Example of catch procedure
+.LP
+.nf
 .ta 1n 24n
 	pro $catch,0	; Local procedure that must catch the overflow trap
 	lol 2	; Load trap number
@@ -168,4 +165,5 @@ Example of catch procedure
 	trp	; call other trap procedure
 	rtt	; if other procedure returns, do the same
 	end
-.DE
+.KE
+.fi

+ 24 - 19
doc/em/types.nr

@@ -1,6 +1,6 @@
-.SN 6
-.BP
-.S1 "TYPE REPRESENTATIONS"
+.bp
+.P1 "TYPE REPRESENTATIONS"
+.PP
 The representations used for typed objects are not precisely
 specified by EM.
 Sometimes we only specify that a typed object occupies a
@@ -15,7 +15,7 @@ on the same object(s).
 For example, the instruction ZER pushes signed and
 unsigned integers with the value zero and empty sets.
 ZER has as only argument the size of the object.
-.A
+.QQ
 The representation of floating point numbers is a good example,
 it allows widely varying implementations.
 The only ways to create floating point numbers are via
@@ -26,13 +26,14 @@ be converted to human readable output.
 Implementations may use base 10, base 2 or any other
 base for exponents, and have freedom in choosing the range of
 exponent and mantissa.
-.A
+.QQ
 Other types are more precisely described.
 In the following paragraphs a description will be given of the
 restrictions imposed on the representation of the types used.
 A number \fBn\fP used in these paragraphs indicates the size of
 the object in \fIbits\fP.
-.S2 "Unsigned integers"
+.P2 "Unsigned integers"
+.PP
 The range of unsigned integers is 0..
 .Ex 2 "\fBn\fP" -1.
 A binary representation is assumed.
@@ -47,20 +48,21 @@ This of course means that some sequences of instructions have
 unpredictable effects.
 For example:
 .DS
-   LOC 258 ; STL 0 ; LAL 0 ; LOI 1      ( wordsize >=2 )
+LOC 258 ; STL 0 ; LAL 0 ; LOI 1      ( wordsize >=2 )
 .DE
 The value on the stack after executing this sequence
 can be anything,
 but will most likely be 1 or 2.
-.A
+.QQ
 Conversion between unsigned integers of different sizes have to
 be done with explicit convert instructions.
 One cannot simply pad an unsigned integer with zero's at either end
 and expect a correct result.
-.A
+.QQ
 We assume existence of at least single word unsigned arithmetic
 in any implementation.
-.S2 "Signed Integers"
+.P2 "Signed Integers"
+.PP
 The range of signed integers is
 .Ex \-2 "\fBn\fP\-1" ~..
 .Ex 2 "\fBn\fP\-1" \-1,
@@ -75,29 +77,31 @@ range
 In other words, the most significant bit is used as sign bit.
 The convert instructions between signed and unsigned integers
 of the same size can be used to catch errors.
-.A
+.QQ
 The value 
 .Ex \-2 "\fBn\fP\-1" 
 is used for undefined
 signed integers.
 EM implementations should trap when this value is used in an
 operation on signed integers.
-The instruction mask, accessed with SIM and LIM \-~see chapter 9~\- ,
+The instruction mask, accessed with SIM and LIM \-~see chapter 9~\-,
 can be used to disable such traps.
-.A
+.QQ
 We assume existence of at least single word signed arithmetic
 in any implementation.
-.S2 "Floating point values"
+.P2 "Floating point values"
+.PP
 Floating point values must have a signed mantissa and a signed
 exponent.
 Although no base is specified, base 2 is the normal choice,
 because the FEF instruction pushes the exponent in base 2.
-.A
+.QQ
 The implementation of floating point arithmetic is optional.
 The compilers currently in use have runtime parameters for the
 size of the floating point values they should use.
 Common choices are 4 and/or 8 bytes.
-.S2 Pointers
+.P2 Pointers
+.PP
 EM has two kinds of pointers: for instruction and for data
 space.
 Each kind can only be used for its own space, conversion between
@@ -109,13 +113,14 @@ One can of course not expect to be able to address two megabyte
 of memory using a 2-byte pointer.
 Normally, a 2-byte pointer allows up to 65536 bytes of
 addressable memory.
-.A
+.QQ
 Pointer representation has one restriction.
 The pointer with the same representation as the integer zero of
 the same size should be invalid.
 Some languages and/or runtime systems represent the nil
 pointer as zero.
-.S2 "Bit sets"
+.P2 "Bit sets"
+.PP
 All bit sets of size \fBn\fP are subsets of the set
 {~i~|~i>=0,~i<\fBn\fP~}.
 A bit set contains a bit for each element showing its
@@ -129,7 +134,7 @@ The relation between a set with size of
 a word and an unsigned integer word is that
 the value of the unsigned integer is the summation of the
 2\v'-0.5m'i\v'0.5m' where i is in the set.
-.A
+.QQ
 Example: a 2-word bit set (wordsize 2) containing the
 elements 1, 6, 8, 15, 18, 21, 27 and 28 is composed of two
 integers, e.g. at addresses 40 and 42.