Editing Simplified Instructional Computer (section)

== SIC Assembly Syntax ==
SIC uses a special assembly language with its own operation codes that hold the hex values needed to assemble and execute programs. A sample program is provided below to get an idea of what a SIC program might look like. In the code below, there are three columns. The first column represents a forwarded symbol that will store its location in memory. The second column denotes either a SIC instruction (opcode) or a constant value (BYTE or WORD). The third column takes the symbol value obtained by going through the first column and uses it to run the operation specified in the second column. This process creates an object code, and all the object codes are put into an object file to be run by the SIC machine.

<CODE><pre>
       COPY   START  1000
       FIRST  STL    RETADR
       CLOOP  JSUB   RDREC
              LDA    LENGTH
              COMP   ZERO
              JEQ    ENDFIL
              JSUB   WRREC
              J      CLOOP
       ENDFIL LDA    EOF
              STA    BUFFER
              LDA    THREE
              STA    LENGTH
              JSUB   WRREC
              LDL    RETADR
              RSUB
       EOF    BYTE   C'EOF'
       THREE  WORD   3
       ZERO   WORD   0
       RETADR RESW   1
       LENGTH RESW   1
       BUFFER RESB   4096
       .
       .      SUBROUTINE TO READ RECORD INTO BUFFER
       .
       RDREC  LDX    ZERO
              LDA    ZERO
       RLOOP  TD     INPUT
              JEQ    RLOOP
              RD     INPUT
              COMP   ZERO
              JEQ    EXIT
              STCH   BUFFER,X
              TIX    MAXLEN
              JLT    RLOOP
       EXIT   STX    LENGTH
              RSUB
       INPUT  BYTE   X'F1'
       MAXLEN WORD   4096
       .
       .      SUBROUTINE TO WRITE RECORD FROM BUFFER
       .
       WRREC  LDX    ZERO
       WLOOP  TD     OUTPUT
              JEQ    WLOOP
              LDCH   BUFFER,X
              WD     OUTPUT
              TIX    LENGTH
              JLT    WLOOP
              RSUB
       OUTPUT BYTE   X'06'
              END    FIRST
</pre></CODE>

If you were to assemble this program, you would get the object code depicted below. The beginning of each line consists of a record type and hex values for memory locations. For example, the top line is an 'H' record, the first 6 hex digits signify its relative starting location, and the last 6 hex digits represent the program's size. The lines throughout are similar, with each 'T' record consisting of 6 hex digits to signify that line's starting location, 2 hex digits to indicate the size (in bytes) of the line, and the object codes that were created during the assembly process.

<CODE><pre>
       HCOPY 00100000107A
       T0010001E1410334820390010362810303010154820613C100300102A0C103900102D
       T00101E150C10364820610810334C0000454F46000003000000
       T0020391E041030001030E0205D30203FD8205D2810303020575490392C205E38203F
       T0020571C1010364C0000F1001000041030E02079302064509039DC20792C1036
       T002073073820644C000006
       E001000
</pre></CODE>