Integer BASIC

Integer BASIC. It was the original BASIC interpreter for the Apple I and early Apple II computers, created by Steve Wozniak to showcase the machines' capabilities. Unlike later versions, it was optimized for speed and supported only integer arithmetic, which suited early hobbyist applications and games. Its tight integration with the hardware made it a foundational element of the Apple II series' initial success.

History and development

The language was hand-assembled by Steve Wozniak directly into the 6502 machine code during the development of the Apple I in 1976. Wozniak's primary goal was to create a fast, efficient interpreter that would fit into the limited ROM of the early machines, a necessity given the constraints of the Apple I's design. Following the success of the Apple I, it was included in the ROM of the original Apple II upon its launch at the West Coast Computer Faire in 1977. However, due to its lack of floating-point support, Apple Inc. later licensed Microsoft's Applesoft BASIC to meet demand for more advanced mathematical and business applications, leading to its eventual phase-out.

Features and characteristics

A key feature was its exclusive use of 16-bit signed integer arithmetic, with numbers ranging from -32768 to 32767, which allowed for exceptionally fast execution compared to interpreters handling Floating-point arithmetic. It included commands for direct manipulation of the Apple II's high-resolution graphics mode, enabling the creation of colorful shapes and games like the famous Breakout (video game). The interpreter also provided PEEK and POKE commands for direct access to memory-mapped hardware, such as the speaker and game I/O socket. Error handling was minimal, with distinctive messages like "*** SYNTAX ERR" and "*** BAD BRANCH ERR" that became familiar to early programmers.

Syntax and programming model

The syntax was line-oriented and used standard BASIC keywords like GOTO, GOSUB, and FOR...NEXT loops for program control. Variable names were limited to two characters, where the first was a letter and the second could be a letter or digit, a constraint designed to save memory. Arrays were single-dimensional and dynamically dimensioned upon first use with a simple DIM statement. A notable quirk was the requirement for spaces between keywords and operands, unlike some contemporary BASIC dialects, which could lead to cryptic syntax errors for users familiar with other systems like Commodore BASIC.

Impact and legacy

It was instrumental in establishing the Apple II as a premier platform for hobbyist programming and software distribution in the late 1970s. Many early commercial programs, including games from publishers like Broderbund and Sir-Tech, were originally written in this language before being ported to Applesoft BASIC or Assembly language. Its design philosophy of speed and hardware access directly influenced the culture of demo coding and game development on the platform. While superseded by Applesoft BASIC, it remained in use by enthusiasts and was later revived in projects like the Apple I Replica Creation and emulators such as MESS.

Example code

A typical program to draw a colored shape might utilize the Apple II's high-resolution graphics commands unique to this interpreter. ``` 10 HGR 20 HCOLOR=3 30 FOR X = 0 TO 279 40 HPLOT X, 0 TO X, 191 50 NEXT X 60 END ``` This simple program, which fills the screen with vertical lines, demonstrates the direct, low-level access to the graphics system. Another common example involved generating sound through the speaker using POKE commands to specific memory addresses, a technique used in many early games. Such code snippets were frequently published in magazines like Byte (magazine) and Creative Computing, spreading programming knowledge.

Category:BASIC interpreters Category:Apple II software Category:1976 software