SIC Assembler

2-Pass Assembler with support for USE and Literals

Purpose

The purpose of this project is to implement both pass 1 and pass 2 of the SIC assembler. The program uses a hash table to maintain a list of valid mnemonics and a separate hash table to store labeled instructions with their computed addresses. The program parses instructions based off a grammar in order to differentiate between labeled and unlabeled instructions, and directives and instructions, as well as different types of operands. Pass 1 iterates through the file and transforms it into an intermediate format that is then iterated through by Pass 2.

This assembler supports the following assembler features:

BASE (input2.txt and input3.txt)
USE blocks (input5.txt)
Literals/LTORG (input6.txt)

Source files

Source files are located at src/main/kotlin/so/roth/cop3404/assembler. The important files and directories are:

grammar\                 Contains data classes that model the SIC instructions
AddressAssigner.kt       Contains pass 1 logic
ObjectCodeAssembler.kt   Performs pass 2 logic
Main.kt			 Main method

Input

The program requires an input file to be passed in as the first argument. The input file is the SIC program that is to be assembled. The input program will need to adhere to the following format:

Col 1-8    Label (optional)
Col 9      Blank
Col 10     + or * (optional)
Col 11-17  Mnemonic
Col 18     Blank
Col 19     #, @, = (optional)
Col 20-29  Operand
Col 30-31  Blank
Col 32-80  Comments (optional)

The test files for the program are located at src/test/resources/input.txt.

src/test/resources/input1.txt - Error handling
src/test/resources/input2.txt - General purpose testing
src/test/resources/input3.txt - General purpose testing
src/test/resources/input4.txt - SIC loader source code
src/test/resources/input5.txt - USE blocks
src/test/resources/input6.txt - Literals / LTORG

Output

The program will output two files: pgm.lst and pgm.asm. If there were any assembler errors, they will be reported in the .lst file and a message will be displayed in the console.

The following errors will also be reported:

Instructions without labels
Invalid mnemonics
Invalid operands
Duplicate labels
Unresolvable label operands
Missing BASE

There are sample corresponding output .lst and .obj files for each of the six input files in the src/test/resources/ directory.

How to execute

The project was developed using Gradle, but can be built with the Kotlin compiler directly. The compiler is automatically installed locally during the first make, which will output a JAR that can be executed on the JVM.