PL/0 Machine

This is one of my most favorite projects that I've done. A compiler made in class that targets the pl/0 educational programming language. Compiles down to a custom 'interpreted' assembly ran by a virtual machine (vm) made in class.

Features

Variable Declarations

Constants

Constants can be declared but not reassigned.

const u = 5;

Variables

variables can be declared and reassigned and even assigned to each other.

var x, y;
y := 5;
y := 6;
x := 8;

x := y + 2;

Functions

Functions are declared by procedure and their name. They can be called later with the keyword "call"

procedure functionname;
    ...
;

call functionname

Recursive calls

Functions can be called within themselves and all their variables and other information will persist on the call stack.

procedure recursiveFunction;

    call recursiveFunction;

;

Comments

As always needed for documentation, comments.

/*this is a comment*/
begin
    ...
end.

 

How to run

• Compile the compiler.c and the vm.c program

$ gcc compiler.c -o compiler

$ gcc vm.c -o vm

• Run the compiler with the desired input file

$ ./compiler <input file>

• This will create a "tokens.txt" file and an "elf.text" file
• Run the vm executable along with the elf.text file that was created earlier

$ ./vm elf.text

And you should get a runnable program that shows each instruction executed and a cool representation of the call stack, and other machine code info.

 

Pictures

Showing the assembly code generated by the compiler
And a short example of the code trace when ran by the Virtual Machine

 

Contributors

• Romsev Charles
• Brandon Sheridan