Writing R3X programs in assembly

A basic sketch

The basic structure of an R3X program is:

include 'libR3X/libR3X.pkg' ; Located in src/programs/
.text {
	; Text section
	function main
		; A main function is mandatory for programs, not for dynamic libraries.
	endfunction main
}
.data {
	; Data Section
}
.bss {
	; BSS Section
}

Text Section: This section contains code, which is to be executed.
Data Section: This section contains data, and hence cannot be written to.
BSS Section: This section contains uninitialised data. This region is both readable and writable. It is zeroed when the VM starts execution.
function: Functions are blocks of code, which can be called. The VM's BIOS calls the main function after initialisation .

Assembling

Assembling must be done using Flat Assembler, assuming you have set up the environment correctly, you just have to:

 
fasm myfile.asm

And you should get a 'myfile.exe' which can now be executed as by the Virtual Machine.

Dynamic Libraries

A basic sketch of a dynamic library is very similar to the program sketch, but a few things are different:

include 'libR3X/dynR3X.pkg'
.text {

}
.data {

}
.bss {

}

Unlike programs a main function is not required. But if you are addressing local variables, you must add R20 to the address. This is because dynamic libraries are designed to be loaded at any point, and hence need to be relocatable. Whenever, the VM calls a dynamic library function, it sets R20 to the load address of the library.