SAL-8 is an interpreted 8-bit simple assembly-like language designed to be embedded in games or other projects. More specifically, it was created for games which revolve around solving programming challenges.
This is a cross-platform C99 implementation of SAL-8, in the form of a library. A simple main.c file for generating an executable is also included.
SAL-8 is an 8-bit language. Therefore, 8-bit numbers (0-255) are the only available data type.
All of the instructions are executed by a virtual machine. Each virtual machine gives the programmer access to two types of resources: a stack, and multiple registers.
- a register simply holds an 8-bit number
- the stack can hold multiple 8-bit numbers, but only the last one is directly accessible.
The registers can be directly referenced, while the stack can be manipulated via the PUSH and POP operations.
The number of registers and the stack size can be specified when creating a virtual machine. However, the usual values are 4 registers and a stack size of 8. These usual values are also used by the provided main.c file.
There is also a special register called CMP, which stores the result of the last CMP operation:
- 0, if the operands are equal
- 1, if the left operand is below the right one
- 2, if the left operand is above the right one
To run a SAL-8 file with the executable, simply pass the path to the file as the first argument.
sal8 <FILE>Each instruction is written on a separate line, and has the following form.
<OP> [LEFT] [, RIGHT]
The list of all operations is listed in a table below.
Comments are preceded by the # character.
# Single-line comment.Labels can be created in the following way.
<label_name>:
To refer to a label, simply write the label name without :.
To refer to a register, use the Rn syntax, where n is the register number (e.g. R0, R3).
Legend:
- R - register
- N - 8-bit number (0-255)
- L - label
The result is stored in the left register (if applicable).
| OP | Left | Right | Description |
|---|---|---|---|
| ADD | R | R/N | Adds the right number/register to the left register |
| AND | R | R/N | Applies the bitwise AND operator on the left register and the right number/register |
| CMP | R/N | R/N | Compares a register/number value with another register/number value, and stores the result in the CMP register |
| DIV | R | R/N | Divides the left register value by the right number/register value |
| IN | R | - | Reads an 8-bit number from STDIN (or IO interface), and stores it in the left register (if there is no more input, the VM is halted) |
| JA | L | - | Checks the CMP register, and jumps to the specified label if the left operand is above the right |
| JAE | L | - | Similar to JA, but also jumps if the two operands are equal |
| JB | L | - | Similar to JA, but jumps only if the first operand is below the first |
| JBE | L | - | Similar to JB, but also jumps if the two operands are equal |
| JE | L | - | Similar to JA, but jumps only if the operands are equal |
| JMP | L | - | Jumps to the specified label |
| MOD | R | R/N | Applies the mod operator between the left register and right number/register |
| MOV | R | R | Copies the right register value in the left register |
| MUL | R | R/N | Multiplies the left register value by the right number/register value |
| NOT | R | - | Applies the bitwise NOT operator on the left register value |
| OR | R | R/N | Applies the bitwise OR operator on the left register value and right number/register value |
| OUT | R/N | - | Writes the left register/number value to STDOUT (or IO interface) |
| SHL | R | R/N | Applies the left shift operator on the left register value, with the right register/number value as the shift count |
| SHR | R | R/N | Similar to SHL, but shifts to the right |
| POP | R | - | Pops the stack and stores the popped element in the left register |
| PUSH | R/N | - | Pushes the left register/number value onto the stack |
| SUB | R | R/N | Subtracts the right register/number value from the left register |
| XOR | R | R/N | Applies the bitwise XOR operator on the left register value and the right register/number value |
Reads numbers and outputs them.
_loop:
IN R0 # Read a number and store it in the first register. If there is no more input, or the input is invalid, the VM will be halted.
OUT R0 # Output the number stored in the first register.
JMP _loop # Jump back.Reads a number n and prints all numbers from n to 0 (inclusive).
IN R0
ADD R0, 1 # The number is first subtracted, so add 1 to the initial number.
loop:
SUB R0, 1 # 0 needs to be included. Subtracting 1 from 0 gives 255. So, first subtract, print, and then check.
OUT R0
CMP R0, 0
JA loopReads 8 numbers and prints them in reverse order.
MOV R0, 0
_input_loop:
IN R1
PUSH R1 # Read each number and push it onto the stack.
ADD R0, 1
CMP R0, 8
JB _input_loop
MOV R0, 8
_output_loop:
POP R1 # Pop each number from the stack and output it.
OUT R1
SUB R0, 1
CMP R0, 0
JA _output_loop
This project was created by The Exom Developers. It is licensed under the MIT license.