Applesoft BASIC lets an Apple II calculate with floating-point numbers and draw through commands such as HGR and HPLOT. Apple’s August 1978 Applesoft II Reference Manual identifies the language as extended-precision floating-point BASIC. Its title pages carry both Apple and Microsoft copyrights.
That ancestry connects it to Microsoft BASIC, but the Apple-specific commands are part of what makes an Applesoft program belong to an Apple II.
Numbers beyond integers
Integer BASIC and Applesoft are different interpreters. Applesoft’s floating-point numbers can represent fractions and a much wider scale of magnitudes than a small integer alone. The representation still has finite precision: decimal-looking arithmetic does not guarantee that every decimal fraction is stored exactly.
A program written for one interpreter cannot be judged compatible just because both accept PRINT or GOTO. The available operations, stored program representation and memory use have to match. The Apple II family’s ROM arrangements also changed, so the interpreter present in a particular machine matters. (Apple, Reference Manual; Applesoft II Reference Manual.)
Commands that know the display
Graphics statements turn a BASIC request into work for the Apple’s video system. HGR selects a high-resolution display arrangement and clears its graphics area; HPLOT draws points and lines. The manual distinguishes configurations, including a restriction on using high-resolution graphics with the cassette implementation because of the memory areas involved.
That detail is a reminder that a command list is only part of a language environment. A graphics screen consumes RAM, the interpreter occupies memory, and machine-code routines or data may need protected space. HIMEM: changes the upper boundary available to BASIC; it does not create additional physical RAM.
BASIC and disk software are separate layers
The reference describes BASIC’s statements and its interfaces. Disk operations also depend on the disk operating system installed around the interpreter. A disk command encountered in an Apple listing is not automatically a standard statement implemented by every Applesoft configuration.
The same caution applies when moving a listing from Commodore or MSX BASIC. Arithmetic and loop ideas can travel, but a POKE address or a graphics keyword needs translating for the destination. Applesoft is useful evidence of how one interpreter family was adapted to a particular computer, rather than a universal home-computer language with identical hardware underneath it.
Sources
- Apple Computer, Applesoft II Reference Manual, August 1978, part A2L0006X: language, graphics, memory and cassette/ROM qualifications. Apple documentation collection.
- Apple Computer, Apple II Reference Manual: machine memory and Integer BASIC context. Original Apple II manuals.