Applesoft BASIC programming language

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The first BASIC programming language dialect on the Apple II computer was Integer Basic, coded and hand-assembled by Apple Computer employees. It could only handle numbers between -32767 and 32767 and had some limitations with respect to string arrays, but it was fast.

Enter Bill Gates and Microsoft. Apple was looking for a new version of Basic for the Apple II Plus computer with 48 KB of RAM. It seems Microsoft was the Basic vendor of choice at the time; Apple licensed a 10 KB assembly language version of Basic called "Applesoft." It was similar to Basic implementations on other 6502-based computers: it used line numbers, spaces were not necessary in lines, plus it had some killer features that Integer BASIC lacked:

  • atomic strings. A string is no longer an array of characters (like in C); it's now a garbage-collected object (like in Scheme and the Java programming language). This allows for string arrays; DIM A$(10) got you a vector of ten string variables.
  • multidimensional arrays.
  • single-precision floating point variables with an 8-bit exponent and a 31-bit significand. Along with this came a trigonometry library.
  • high-resolution graphics.
  • CHR$, ASC, STR$, and VAL functions for converting between string and numeric types
  • no more writing LET

Why weren't many action games written in Applesoft Basic?

  • Integer variables had to be converted to reals before math could be performed on them; they were then converted back to integers. Slow. Microsoft forgot to special case this.
  • So-called shape tables are a poor alternative to bitmaps. No provision for mixing text and graphics. No provision was added in the 128 KB Apple IIe and Apple IIc models' Basic interpreters for the new machines' double-resolution graphics, or for the Apple IIGS computer's 16-color mode. (Beagle Bros offered machine-language workarounds for these problems.)
  • The program was stored as a list of lines; a GOTO took O(n) (linear) time.
  • No sound support.
  • The closed source movement was just beginning; software publishers found it was harder to crack a compiled binary than an interpreted source.

Here's Hello World in Applesoft Basic: