Ben-Avrahami / Assembler-OpenU

Open University Semester 2022 A System Programming in C language Project-Assembler

Assembler-OpenU

The final assignment (#14) of the C course (20465) at The Open University.

Semester 2022 A

Done by Ben Avrahami and Gal Ben Artzi

The Project was graded 100!

Getting Started

The project was coded and compiled using Ubuntu, but it may run on all Linux versions.

Usage

Use makefile to compile the project like this:

make

After preparing assembly files with an .as extension, open terminal and pass file names as arguments (without the file extensions) as following:

As for the files x.as, y.as, hello.as we will run:

assembler x y hello

The assembler will generate output files with the same filenames and the following extensions:

• .ob - Object file

• .ent - Entries file

• .ext - Externals file

An example of input and output files can be found under the 'tests' folder.

Directives

A directive line of the following structure:

1. An optional preceding label. e.g. PLACE1: .

2. A directive: .data, .string, .struct, .entry or .extern.

3. Operands according to the type of the directive.

   .data

   This directive allocates memory in the data image for storing received integers later in memory (also increases the data counter and updates the symbol table). The parameters of .data are valid integers (separated by a comma).
   e.g. LABEL1: .data +7, -56, 4, 9.

   .string

   This direcive receives a string as an operand and stores it in the data image. It stores all characters by their order in the string, encoded ny their ASCII values. e.g. STRING1: .string "abcdef" is a valid directive.

   .entry

   This directive outputs a received name of a label to the symbol table, so that later it will be recognized by other assembly files (and they would be able to use it). e.g.

   ; file1.as
   .entry HELLO
   HELLO: add #1, r1 
   

   .extern

   This directive receives a name of a label as a parameter and declares the label as being external (defined in another file) and that the current file shall use it.
   This way, the directive .extern HELLO in file2.as will match the .entry directive in the previous example.