| mnemonic |
opcode (number) |
memory words |
description |
| halt |
0 |
1 |
halt
the program no longer executes,
and exits (using the Linux system-call)
with the integer on the TOS as the program's exit status |
| nop |
1 |
1 |
no operation
the PC is advanced to the next instruction |
| add |
2 |
1 |
addition
the two integers on the TOS are popped from the stack,
added together,
and the result left on the TOS |
| sub |
3 |
1 |
subtraction
the two integers on the TOS are popped from the stack,
the second subtracted from the first,
and the result left on the TOS |
| mult |
4 |
1 |
multiplication
the two integers on the TOS are popped from the stack,
multiplied together,
and the result left on the TOS |
| div |
5 |
1 |
division
the two integers on the TOS are popped from the stack,
the second divided from the first,
and the result left on the TOS |
| call |
6 |
2 |
function call
the word following the 'call' instruction holds the address of
the required function's first instruction.
The function's first instruction is the next instruction to
be executed |
| return |
7 |
2 |
function return
the flow of execution returns to the instruction immediately
following the 'call' instruction that called the current function.
The integer value on the TOS is the function's returned value
(even if the current function is of type void).
The value immediately following the return opcode
indicates where the function's returned value should be copied
before the function returns -
to the location of FP+value of the current function's stack frame. |
| jmp |
8 |
2 |
unconditional jump
the flow of execution continues at the address in the word immediately
following the 'jmp' instruction |
| jeq |
9 |
2 |
conditional jump
the value on the TOS is popped from the stack and,
iff the value is zero,
the flow of execution continues at the address in the word immediately
following the 'jeq' instruction |
| printi |
10 |
1 |
print integer
the value on the TOS is popped from the stack and
printed to stdout |
| prints |
11 |
2 |
print string
the NULL-byte terminated character string
whose address immediately follows the 'prints' instruction
is printed to stdout |
| pushc |
12 |
2 |
push integer constant
the integer constant in the word immediately following the 'pushc'
instruction is pushed onto the stack |
| pusha |
13 |
2 |
push absolute
the word immediately following the 'pusha' instruction
holds the address of the integer value to be pushed onto the stack |
| pushr |
14 |
2 |
push relative
the word immediately following the 'pushr' instruction
provides the offset to be added to the FP
to provide the address of the integer value to be pushed onto the stack |
| popa |
15 |
2 |
pop absolute
the word immediately following the 'popa' instruction
holds the address into which the value on the TOS should be popped |
| popr |
16 |
2 |
pop relative
the word immediately following the 'popr' instruction
provides the offset to be added to the FP
to provide the address into which the value on the TOS should be popped |
