fasm

Fake assembly

This is a fake assembly language. It is used for educational purpose only.

To run this program you need Golang installed in your machine. Then run:

$ go run . ./examples/a1.asm

The target file name must end with .asm.

How to access memory

We limit the memory to have only 1024 slots. Every slot is initialized with 0.

1. Constants

To use constants you just need to use a number without any prefix. Like:

123
321

Are all constants

2. Variables

A variable is a direct access to memory, you can do that by just adding the prefix $ and an index for the position that you want to access. Suppose that your memory look like this [4,3,6,7,8] so:

$1 # Here you are accessing the memory indexed by 1 so of this is 3
$0 # Here you are accessing the memory indexed by 0 so of this is 4

3. Reference

Reference is an indirect access to memory, where a variable will define the slot position that you want to access. Again suppose that the memory look like this [2,3,8,7] so:

&1 # Here you use the memory at '1'(value == 3) as an index, similar to memory[memory[1]] = 7
&0 # Here you use the memory at '0'(value == 2) as an index, similar to memory[memory[0]] = 8

Instructions

1. Operation

Write the result of the operation {C, $, &}1 {-, +, *, /} {C, $, &}2 to memory {$, &}0.

$0 = 232 + &12
&1 = $12 / 2

2. Label

To define a label you can do that by just

{label}:

Replace {label} with an appropriate value.

3. To

Change the code flow if the predicate is true the pattern is to {label} if {C, $, &}1 {==, !=, >, <, >=, <=} {C, $, &}1 {&&, ||} ....

to main if 1 == 1

some_label:
  $0 = $0 + 1
  to main if &1 <= &2 || $1 > 2

main:
  $0 = $0 - 1
  to some_label if $0 > 1 && $0 < 12

5. Write

Print a value. Suppose that your memory looks like this [1,2,3,4,5].

print 1 # Will print `$ 1`
print $1 # Will print `$ [ 1 ] 2`
print &1 # Will print `$ [ 1 -> 2 ] 3`

6. Read

Read a value from the input file. Will jump to the label provided if unable to read(optional).

read $0
read $0 end
read $0 end

end:
  write $0