SIC/XE Assembler

Overview

• SIC/XE is a hypothetical architecture introduced in System Software: An Introduction to Systems Programming, by Leland Beck to explain the concepts of assemblers, compilers, and operating systems [1; 2].
• The sicasm.c program implements a two-pass assembler for the SIC (Simplified Instructional Computer) machine architecture.
• The sicxeasm.c program implements a two-pass assembler for the SIC/XE (Simplified Instructional Computer with Extra Equipment) machine architecture.
• Both programs read an assembly language program for the SIC or SIC/XE machines respectively, process it, and produce three output files:
  • Intermediate File: A temporary file that can be safely deleted. It contains the source code and is utilized to generate the listing and object code files.
  • Listing File: This file contains the source code along with the corresponding object code (in hexadecimal) generated for each statement. It also includes a symbol table that lists all symbols and their corresponding addresses after the assembly process.
  • Object Code File: This file contains the final object code generated by the assembler, formatted according to SIC/XE standards. It includes a Header record, Text records, and an End record.
• The program handles basic directives and opcodes in the SIC/XE instruction set and performs error checking during both passes of the assembly process.

Features

• Pass 1:
  • Parses the assembly source code to generate a symbol table and track location counters.
  • Checks for duplicate symbols and invalid opcodes.
• Pass 2:
  • Generates object code based on the symbol table and processes each statement.
  • Checks for undefined symbols and errors related to operand formats.
• Supported Directives: START, BYTE, WORD, RESB, RESW, END, BASE, NOBASE
• Supported Opcodes: A range of SIC/XE machine opcodes such as ADD, SUB, LDA, STA, JSUB, RD, TD, RSUB, and more.
• Input Format: The source file is a text file containing assembly instructions, comments, labels, opcodes, and operands formatted according to SIC/XE conventions.
• Output Format:
  1. An intermediate file (temporary file that can be safely deleted) containing:
     • Line numbers
     • Location counter values
     • Source statements
  2. A listing file containing:
     • Line numbers
     • Location counter values
     • Source statements
     • Object code
     • Symbol table
  3. An object file containing the final assembled object code

Setup & Usage

1. Ensure the following prerequisites are installed:
   • C Compiler (e.g., GCC, MSVC)
   • Command-line interface to run the assembler program
   • Standard C libraries: stdio.h, stdlib.h, string.h, stdbool.h
2. Compile the source code into an executable:

   gcc sicasm.c -o sicasm

   gcc sicxeasm.c -o sicasm

3. Run the assembler with the input assembly source code file:

   ./sicasm SIC_PROG.txt

   ./sicxeasm SIC_PROG.txt

4. Each program will generate three output files:
   • sic_intermediate.txt, sic_listing.txt, and sic_object.txt
   • sicxe_intermediate.txt, sicxe_listing.txt, and sicxe_object.txt

Sample Program Inputs & Outputs

• Sample input and output files are included in the repository for reference in the SIC sample_io and SIC_XE sample_io folders.
• sicasm.c Program:
  • Input: SIC_PROG.txt
  • Outputs: sic_immediate.txt, sic_listing.txt, sic_object.txt
• sicxeasm.c Program:
  • Input: SIC_XE_PROG.txt
  • Outputs: sicxe_immediate.txt, sicxe_listing.txt, sicxe_object.txt

References

[1] Beck, L. L. (1997). System Software: An Introduction to Systems Programming (3rd ed.). Addison-Wesley.
[2] Wikimedia Foundation. (2024, December 16). Simplified Instructional Computer. Wikipedia. https://en.wikipedia.org/wiki/Simplified_Instructional_Computer

Authors

This project was collaboratively developed by Hannah G. Simon and Charlie Strickland.