Intermediate Script Object

ISO is a minimal stack-oriented instruction format intended for embedded applications. It has a very simple Forth-like syntax, enough to write any programs sufficiently.

Examples

Each statement consists of a block followed by literal value(s), depending on the type of block.

Annotations are done by using the REM block

REM "This is a comment and does not do anything"

Pushing two numbers to the stack and adding them together

NUM 1 2
ADD

Defining and calling a function

FUN "SUBTRACT","C","A","B"
    VAR "A" GET REM "Arguments are passed by reference."
    VAR "B" GET REM "VAR returns the pointer and GET pushes the value from that address"
    SUB
    VAR "C" SET
    RET         REM "Must return at end of the function or else it will fall through"

NUM 0 1 2       REM "0 is a placeholder value"
RUN "SUBTRACT"  REM "Call the SUBTRACT subroutine"
POP POP         REM "Pop arguments from the stack, leaving only the result"

Interfacing with the host

ISO uses interrupts in order to communicate with the host program. Interrupts simply halts the VM and allows the host to perform any necessary actions before resuming.

As an example, assume 0x1234 is the print interrupt routine

POS GBL "Text" SET REM "Assigns current stack pointer to global variable"
NUM "Hello World!" 0

GBL "Text" GET     REM "Push pointer to the stack"
NUM 0x1234 INT     REM "Request host to print characters from that address"
...                REM "VM resumes executing instructions"

In C this may look like:

do {
    iso_vm_run(&vm);
    do_io_stuff(&vm); /* Sets INT back to 0 */
} while (!vm.INT);

Blocks (mnemonics)

Most blocks directly translates to bytecode with a few exceptions.

Table of blocks and their corresponding opcode:

NUM [0x00 - 0x0F] INT [0x10]
JMP [0x20] JMC [0x21] CEQ [0x22] CNE [0x23] CLS [0x24] CLE [0x25]
ADD [0x40] SUB [0x41] MUL [0x42] DIV [0x43] POW [0x44] MOD [0x45]
NOT [0x50] AND [0x51] BOR [0x52] XOR [0x53] LSH [0x54] RSH [0x55]

Floating point extension:

FPU [0x60 - 0x6F]
FTU [0x70] UTF [0x71] FEQ [0x72] FNE [0x73] FLS [0x74] FLE [0x75]
FAD [0x80] FSU [0x81] FMU [0x82] FDI [0x83] FPO [0x84] FMO [0x85]
SIN [0x90] COS [0x91] TAN [0x92] SQR [0x93] LOG [0x94] EXP [0x95]

Macros

Not every block directly translates to a single instruction. Some are macros which help organize the program structure.

List of built-in macros:

REM RAW
SEC REC
GBL VAR
FUN PTR
RUN RET

License

This software is free to use. You can modify it and redistribute it under the terms of the MIT license. Check LICENSE for further details.