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很少见的源码公开的msc51和z80的c编译器。

                .       as a 16-bit word expression,
                .       the high-order byte will be truncated.
                .       Multiple expressions must be


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        GENERAL ASSEMBLER DIRECTIVES


                expn    separated by commas.

           The  .byte  or .db directives are used to generate successive
        bytes of binary data in the object module.  


        1.4.6  .word and .dw Directives 

        Format:  

                .word   exp             ;Stores the binary value
                .dw     exp             ;of the expression in
                                        ;the next word.
        
                .word   exp1,exp2,expn  ;Stores the binary values
                .dw     exp1,exp2,expn  ;of the list of expressions
                                        ;in successive words.
        
        where:  exp,    represent expressions that will occupy two
                exp1,   bytes of data. Each expression will be
                .       calculated as a 16-bit word expression.
                .       Multiple expressions must be
                expn    separated by commas.

           The  .word  or .dw directives are used to generate successive
        words of binary data in the object module.  


        1.4.7  .blkb, .blkw, and .ds Directives 

        Format:  

                .blkb   N       ;reserve N bytes of space
                .blkw   N       ;reserve N words of space
                .ds     N       ;reserve N bytes of space

           The  .blkb  and .ds directives reserve byte blocks in the ob-
        ject module;  the .blkw directive reserves word blocks.  


        1.4.8  .ascii Directive 

        Format:  

                .ascii  /string/ 

        where:  string  is a string of printable ascii characters.  

                /  /    represent   the  delimiting  characters.   These
                        delimiters   may   be   any   paired    printing
                        characters,  as  long  as the characters are not
                        contained within  the  string  itself.   If  the


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        GENERAL ASSEMBLER DIRECTIVES


                        delimiting  characters  do not match, the .ascii
                        directive will give the (q) error.  

        The  .ascii  directive  places  one binary byte of data for each
        character in the string into the object module.  


        1.4.9  .ascis Directive 

        Format:  

                .ascis  /string/ 

        where:  string  is a string of printable ascii characters.  

                /  /    represent   the  delimiting  characters.   These
                        delimiters   may   be   any   paired    printing
                        characters,  as  long  as the characters are not
                        contained within  the  string  itself.   If  the
                        delimiting  characters  do not match, the .ascis
                        directive will give the (q) error.  

        The  .ascis  directive  places  one binary byte of data for each
        character in the  string  into  the  object  module.   The  last
        character in the string will have the high order bit set.  


        1.4.10  .asciz Directive 

        Format:  

                .asciz  /string/ 

        where:  string  is a string of printable ascii characters.  

                /  /    represent   the  delimiting  characters.   These
                        delimiters   may   be   any   paired    printing
                        characters,  as  long  as the characters are not
                        contained within  the  string  itself.   If  the
                        delimiting  characters  do not match, the .asciz
                        directive will give the (q) error.  

        The  .asciz  directive  places  one binary byte of data for each
        character in the string into the object module.   Following  all
        the  character  data  a  zero  byte is inserted to terminate the
        character string.  




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        GENERAL ASSEMBLER DIRECTIVES


        1.4.11  .radix Directive 

        Format:  

                .radix  character 

        where:  character  represents  a single character specifying the
                        default radix to be used for succeeding numbers.
                        The character may be any one of the following:  

                        B,b     Binary
        
                        O,o     Octal
                        Q,q
        
                        D,d     Decimal
                        'blank'
        
                        H,h     Hexidecimal
                        X,x


        1.4.12  .even Directive 

        Format:  

                .even 

           The .even directive ensures that the current location counter
        contains an even boundary value by adding 1 if the current loca-
        tion is odd.  


        1.4.13  .odd Directive 

        Format:  

                .odd 

           The  .odd directive ensures that the current location counter
        contains an odd boundary value by adding one if the current  lo-
        cation is even.  




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        GENERAL ASSEMBLER DIRECTIVES


        1.4.14  .area Directive 

        Format:  

                .area   name    [(options)] 

        where:  name    represents the symbolic name of the program sec-
                        tion.   This  name  may  be  the  same  as   any
                        user-defined  symbol  as  the area names are in-
                        dependent of all symbols and labels.  

                options specify the type of program or data area:  
                        ABS     absolute (automatically invokes OVR) 
                        REL     relocatable 
                        OVR     overlay 
                        CON     concatenate 
                        PAG     paged area 


           The .area directive provides a means of defining and separat-
        ing multiple programming and data sections.   The  name  is  the
        area  label used by the assembler and the linker to collect code
        from various separately assembled modules into one section.  The
        name may be from 1 to 8 characters in length.  

           The options are specified within parenthesis and separated by
        commas as shown in the following example:  

                .area  TEST  (REL,CON)  ;This section is relocatable
                                        ;and concatenated with other
                                        ;sections of this program area.
        
                .area  DATA  (REL,OVR)  ;This section is relocatable
                                        ;and overlays other sections
                                        ;of this program area.
        
                .area  SYS   (ABS,OVR)  ;(CON not allowed with ABS)
                                        ;This section is defined as
                                        ;absolute. Absolute sections
                                        ;are always overlayed with
                                        ;other sections of this program
                                        ;area.
        
                .area  PAGE  (PAG)      ;This is a paged section. The
                                        ;section must be on a 256 byte
                                        ;boundary and its length is
                                        ;checked by the linker to be
                                        ;no larger than 256 bytes.
                                        ;This is useful for direct page
                                        ;areas.



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        GENERAL ASSEMBLER DIRECTIVES


           The  default  area type is REL|CON;  i.e.  a relocatable sec-
        tion which is concatenated with other sections of code with  the
        same area name.  The ABS option indicates an absolute area.  The
        OVR and CON options indicate if program  sections  of  the  same
        name  will overlay each other (start at the same location) or be
        concatenated with each other (appended to each other).  

           Multiple  invocations  of  the  .area directive with the same
        name must specify the same options or leave  the  options  field
        blank,  this  defaults  to  the previously specified options for
        this program area.  
        The   ASxxxx   assemblers   automatically  provide  two  program
        sections:  

                '.  .ABS.'      This dumby section contains all absolute
                                symbols and their values.  

                '_CODE'         This  is  the default program/data area.
                                This program area is of type (REL,CON). 
        The  ASxxxx  assemblers  also automatically generate two symbols
        for each program area:  

                's_<area>'      This is the starting address of the pro-
                                gram area.  

                                indent  -16  'l_<area>'      This is the
                                length of the program area.  


        1.4.15  .org Directive 

        Format:  

                .org    exp 

        where:  exp     is  an absolute expression that becomes the cur-
                        rent location counter.  

        The  .org directive is valid only in an absolute program section
        and will give a (q) error if used in a relocatable program area.
        The  .org  directive specifies that the current location counter
        is to become the specified absolute value.  




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        GENERAL ASSEMBLER DIRECTIVES


        1.4.16  .globl Directive 

        Format:  

                .globl  sym1,sym2,...,symn 

        where:  sym1,           represent legal symbolic names. When
                sym2,...        When multiple symbols are specified,
                symn            they are separated by commas.

           A  .globl directive may also have a label field and/or a com-
        ment field.  

           The  .globl directive is provided to define (and thus provide
        linkage to) symbols not  otherwise  defined  as  global  symbols
        within  a  module.   In  defining  global  symbols the directive
        .globl J is similar to:  

              J == expression or J::  

           Because  object  modules  are linked by global symbols, these
        symbols are vital to a program.  All internal symbols  appearing
        within  a  given program must be defined at the end of pass 1 or
        they will be considered undefined.  The assembly directive  (-g)
        can  be  be  invoked to make all undefined symbols global at the
        end of pass 1.  


        1.4.17  .if, .else, and .endif Directives 

        Format:  

                .if     expr
                .                       ;}
                .                       ;} range of true condition
                .                       ;}
                .else
                .                       ;}
                .                       ;} range of false condition
                .                       ;}
                .endif

           The  conditional  assembly directives allow you to include or
        exclude blocks of source code durin