Computer simulator

This is the simple computer system simulator which started as a course project at Peter the Great St.Petersburg Polytechnic University.

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User interface

Instructions Table

Here's a set of possible mnemonics for the machine codes that the computer recognizes:

Operation	Code	Mnemonic
Load	0b0001	LOD
Store	0b1000	STO
Add	0b0010	ADD
Subtract	0b0011	SUB
Add with Carry	0b0100	ADC
Subtract with Borrow	0b0101	SBB
Jump	0b0110	JMP
Jump If Zero	0b1010	JZ
Jump If Not Zero	0b1001	JNZ
Halt	0b0111	HLT

Examples

There are examples of programs for the simulator below:

First example:

;  Multiply 8-bit values 0xA7 and 0x1C
BEGIN:  LOD A, [RESULT+1] ; Load  byte at address RESULT+1 into accumulator
        ADD A, [NUM1+1]   ; Add byte at address NUM1+1 to accumulator
        STO [RESULT+1], A ; Store contents of accumulator at address RESULT+1

        LOD A, [RESULT]   ; Load  byte at address RESULT into accumulator
        ADC A, [NUM1]     ; Add with carry byte at address NUM1 to accumulator
        STO [RESULT], A   ; Store contents of accumulator at address RESULT

        LOD A, [NUM2+1]   ; Load  byte at address NUM2+1 into accumulator
        ADD A, [DEC]      ; Add byte at address DEC to accumulator
        STO [NUM2+1], A   ; Store contents of accumulator at address NUM2+1

        JNZ BEGIN         ; Jump if not zero to the instruction at BEGIN
        HLT               ; Halt
        
DEC:    FF                ; On the 28 (0x1C) time through value 1 will be added
                          ;  to 0xFF and the result will be zero, so
                          ;  the JNZ instruction will not jump back to BEGIN
                          ;  Instead, the next instruction is a Halt.

NUM1:   00, A7
NUM2:   00, 1C
RESULT: 00, 00            ; 16-bit value goes here

Second example

; Add two 8-bit numbers together and subtract a third
       LOD A, [NUM1]
       ADD A, [NUM1+1]
       SUB A, [NUM1+2]
       STO [SAVE], A
       HLT

NUM1: 45, A9, 8E
SAVE: 00 ; Final result goes here

NOTE: don't try to place labels before or between instructions: it doesn't work temporarily. Type labels only after all commands.