Applesoft BASIC

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Applesoft BASIC was a dialect of BASIC supplied with the Apple II series of computers. It superseded Integer BASIC and was the BASIC in ROM in all Apple II series computers after the original Apple II model. It was also referred to as FP (from "floating point") because of the command used to invoke it instead of INT for Integer BASIC. Applesoft BASIC was supplied by Microsoft and its name is derived from the names of both Apple and Microsoft. Apple employees, including Randy Wigginton, adapted Microsoft's interpreter for the Apple II and added several features. The first version of Applesoft was released in 1977 only on cassette tape and lacked proper support for high-resolution graphics. Applesoft II, which was made available on cassette and disk and in the ROM of the Apple II Plus and subsequent models, was released in 1978. It is this latter version, which has some syntax differences from the first as well as support for the Apple II high-resolution graphics modes, that most people mean by the term "Applesoft."

Contents

Background

Apple's customers were demanding a version of BASIC that supported floating point calculations. As Steve Wozniak, the creator of Integer BASIC and the only person who understood it well enough to add floating point features, was busy with the Disk II drive and controller and with Apple DOS, Apple turned to Microsoft, who was the BASIC vendor of choice after their success with Altair BASIC, and licensed a 10 KB assembly language version of BASIC dubbed "Applesoft." Apple reportedly obtained an eight-year license for Applesoft BASIC from Microsoft for a flat fee of $21,000, renewing it in 1985 through an arrangement that gave Microsoft the rights and source code for Apple's Macintosh version of BASIC.

Applesoft was similar to (and indeed had a common code base with) BASIC implementations on other 6502-based computers, such as Commodore BASIC: it used line numbers, and spaces were not necessary in lines. While Applesoft was slower than Integer BASIC, it had many features that the older BASIC lacked:

  • Atomic strings: A string is no longer an array of characters (as in Integer BASIC and C); it is instead a garbage-collected object (as in Scheme and Java). This allows for string arrays; DIM A$(10) resulted in a vector of eleven string variables numbered 0–10.
  • Multidimensional arrays
  • Single-precision floating point variables with an 8-bit exponent and a 31-bit significand and improved math capabilities, including trigonometry and logarithmic functions
  • Commands for high-resolution graphics
  • CHR$, STR$, and VAL functions for converting between string and numeric types (both languages did have the ASC function)
  • User-defined functions: simple one-line functions written in BASIC, with a single parameter
  • Error-trapping, allowing BASIC programs to handle unexpected errors by means of a subroutine written in BASIC

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