Lazer's Interactive Symbolic Assembler


Lazer's Interactive Symbolic Assembler

Lazer's Interactive Symbolic Assembler (Lisa) is an interactive MOS 6502 assembler for Apple II computers written by Randall Hyde in the late 1970s.

The latest version of Lisa is V3.2. Syntax mistakes can be reported immediately in the edit mode. Lisa can assemble about 30,000 lines of code in a minute on a 1 MHz computer.

Lisa, before v.3, was able to assemble SWEET16 codes, a virtual 16-bit processor implemented as part of the Integer BASIC. However, Apple II's integer ROM was replaced by Monitor ROM since Apple II+.

The assembler also features "Randy's Hi-res Routines", a set of 2D computer graphics commands. Apple II's hi-res display pages (Hi-Res 1: 280 x 160 and Hi-Res 2: 280 x 192) were implemented by Steve Wozniak using two TTL chips. Therefore a software programmer has to deal with the discontinuous addressing of screen pixels (a full screen is split into three parts horizontally) and each pixel's coloring properties (each pixel uses 1-bit, its color is determined by that bit's place in a byte and its neighboring pixel). These ready-made subroutines were created to help programmers.

Lisa has a built-in disassembler.

External links

* [http://www.apple2.org.za/mirrors/apple2.caltech.edu/8bit/dev/lisa/ Authorized Lisa download]


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