To HLL and Back

Applying High Level Language constructs to 6502 Assembly

An occasional series by Michael Martin

This is a series of brief essays explaining how to use HLL constructs from high-level languages to your machine language projects. It uses the 6502 chip to develop its examples, and should be of most use to fledgeling demo/game writers for the NES or Commodore 64.

As of December 2005, the series is basically complete, but feel free to email me comments about the essays or to suggest additional topics.

• The Second Step: extended precision arithmetic, and branch semantics for signed, unsigned, and extended precision. Level: Beginner. Assumes no knowledge beyond knowledge of what the opcodes do. Last updated 9 May 2002.
• Structured Programming: If/then/else constructs, bounded loops (Pascal's for statement), unbounded loops (C's for statement), non-recursive procedures, basic use of the page 1 stack, cursor-based arrays, records, unions, bitfields, global variables, brief coverage of pointers and efficient looping over large areas of memory. Level: Advanced beginner. Assumes basic knowledge of at least one procedural language - C, Pascal, FORTRAN, or any of several advanced BASICs. Knowledge of an object-oriented language that lets you ignore the OO features (C++, Java with everything declared static) should also suffice. Last updated 30 Sep 2002
• Pointers and Indirection: A more comprehensive look at the indirect addressing modes on the 6502 chip and how to use them to implement C-style pointers with arithmetic or the non-computable reference types preferred by many other languages. Level: Intermediate. Assumes a basic understanding of all previous material. Last updated 24 Oct 2002.
• Functionals: Code pointers, object-oriented discipline, dispatch-on-type, jump tables. Level: Intermediate. Assumes basic familiarity with pointers, but full command of the material in the "Indirection" essay is not required. Basic experience with functional languages like LISP or ML and object-oriented languages like C++ or Java may be helpful but is not required. Last updated 16 Aug 2005.
• Call stacks. Implementing and using a full stack, complete with procedure-local variables and allowing for fully recursive functions. Level: Advanced. Full understanding of this and all previous material would be basically sufficient to write a backend for a compiler for C, Pascal, or similar languages. Last updated 28 Nov 2005.