Integer BASIC is a BASIC interpreter written by Steve Wozniak for the Apple I and Apple II computers. Originally available on cassette for the Apple I in 1976, then included in ROM on the Apple II from its release in 1977, it was the first version of BASIC used by many early home computer owners.
The only numeric data type was the integer; floating-point numbers were not supported. Using integers allowed numbers to be stored in a much more compact 16-bit format that could be more rapidly read and processed than the 32- or 40-bit floating-point formats found in most BASICs of the era. This made it so fast that Bill Gates complained when it outperformed Microsoft BASIC in benchmarks. However, this also limited its applicability as a general-purpose language.
Another difference with other BASICs of the era is that Integer BASIC treated strings as arrays of characters, similar to the system in C or Fortran 77. Substrings were accessed using array slicing rather than string functions. This style was introduced in HP Time-Shared BASIC, and could also be found in other contemporary BASICs patterned on HP, like North Star BASIC and Atari BASIC. It contrasted with the style found in BASICs derived from DEC, including Microsoft BASIC.
The language was initially developed under the name GAME BASIC and referred to simply as Apple BASIC when it was introduced on the Apple I. It became Integer BASIC when it was ported to the Apple II and shipped alongside Applesoft BASIC, a port of Microsoft BASIC which included floating-point support. Integer BASIC was phased out in favor of Applesoft BASIC starting with the Apple II Plus in 1979.
History
As a senior in high school, Steve Wozniak's electronics teacher arranged for the leading students in the class to have placements at local electronics companies. Wozniak was sent to Sylvania where he programmed in FORTRAN on an IBM 1130. That same year, General Electric placed a terminal in the high school that was connected to one of their mainframes running their time-sharing BASIC service, which they were heavily promoting at the time. After being given three days of access, the students were asked to write letters on why the school should receive a terminal permanently, but their efforts were ultimately unsuccessful.
Some years later, Wozniak was working at Hewlett-Packard (HP) running simulations of chip designs and logic layout for calculators. HP made major inroads in the minicomputer market with their HP 2000 series machines running a custom timesharing version of BASIC. For approximately , one could build up a reasonably equipped machine that could support between 16 and 32 users running BASIC programs. While expensive, it was still a fraction of the cost of the mainframe machines and, for heavy users, less than the timesharing services. HP followed this with the HP 9830, a desktop-sized machine for that also ran BASIC, which Wozniak had access to.
In January 1975 the Altair 8800 was announced and sparked off the microcomputer revolution. In March, Wozniak attended the first meeting of the Homebrew Computer Club and began formulating the design of his own computer. One of the most important pieces of software for the Altair, and one of the most heavily pirated, was Altair BASIC from the recently formed Microsoft. Wozniak concluded that his machine would have to have a BASIC of its own, which would, hopefully, be the first for the MOS Technology 6502 processor. As the language needed 4 KB RAM, he made that the minimum memory for the design.
Wozniak's references for BASIC were a copy of 101 BASIC Computer Games and an HP BASIC manual. He did not know that HP's BASIC was very different from the DEC BASIC variety used in 101 Games, which was also the basis of Microsoft BASIC for the Altair. Based on these sources, Wozniak began sketching out a syntax chart for the language. The design initially included floating-point support, but still hoping he might publish the first BASIC on the 6502 and become "a star", he decided to abandon floating-point and write a separate integer math system to save a few weeks programming time.