Yet another Little ASM

yla is an custom Assembly-like language, implemented from scratch in C++. Name inspired on my-little-asm deverloped by @alexdantas witch was also deverloped as System Software class assigment at UnB. So far, it has an assembler (to create machine code), a linker, a loader and a simulator.

This is an example on how Assembly languages work - a set of human-readable instructions that are translated into machine code. Normally the language would be designed for some hardware to execute, but in our case we simulate it step by step.

With our basic instruction set we can potentially write any existing program out there - also called Turing-completeness.

We have a parser that reads each instruction on the text file and converts them into integers - indexing all 14 possible instructions.

First, make sure to compile everything by doing:

$ make

Sample code

SECTION TEXT
ROT: INPUT N1
    COPY N1, N4 ; Comentary
    COPY N2, N3
    COPY N3, N3 + 1
    OUTPUT N3 + 1
    STOP

SECTION DATA
N1: SPACE
N3: SPACE  4        ; Array of size 4
N2: CONST  -0x10    ; Look ma, hex constant!

Language definition

yla follows a MIPS Assembly-like syntax.

Highlights:

• 14 instructions.
• ; starts comment until the end of line.
• Labels references memory addresses.
• Accumulator register (ACC) implied on arithmetic instructions.
• Files with .asm extension.

Code is divided in two sections:

• Text section (for actual code)
• Data section (for variables and constants)

Instructions

Name	Instruction	Description
Add	ADD	ACC <- ACC + MEM[OP]
Subtract	SUB	ACC <- ACC - MEM[OP]
Multiply	MULT	ACC <- ACC * MEM[OP]
Divide	DIV	ACC <- ACC / MEM[OP]
Jump Unconditional	JMP	PC <- OP
Jump if Negative	JMPN	If ACC < 0 then PC <- OP
Jump if Positive	JMPP	If ACC > 0 then PC <- OP
Jump if Zero	JMPZ	If ACC = 0 then PC <- OP
Copy	COPY	MEM[OP2] <- MEM[OP1]
Load from Memory	LOAD	ACC <- MEM[OP]
Store into Memory	STORE	MEM[OP] <- ACC
Store Input	INPUT	MEM[OP] <- STDIN
Output Memory	OUTPUT	STDOUT <- MEM[OP]
Stop Execution	STOP	stops program

Note:

• MEM[OP] means memory address specified by operand and PC is the program counter (current instruction address).

Directives

Name	Effect
SECTION TEXT	Signals begin of instructions.
SECTION DATA	Start of data definitions.
SPACE	Saves an empty space on memory for data storage.
SPACE N	Saves an empty array in memory of size N.
CONST X	Saves a constant of value X in memory.
CONST X	Saves a constant of value X in memory.