Apple Pascal

Apple Pascal is an implementation of Pascal for the Apple II and III computer series. It is based on. Just like other UCSD Pascal implementations, it ran on its own operating system (Apple Pascal Operating System, a derivative of UCSD p-System with graphical extensions).

Originally released for the Apple II in August 1979, just after Apple DOS 3.2, Apple Pascal pioneered a number of features that would later be incorporated into DOS 3.3, as well as others that would not be seen again until the introduction of ProDOS.

The Apple Pascal software package also included disk maintenance utilities, and an assembler meant to complement Apple's built-in "monitor" assembler. Silicon Valley Software of Sunnyvale, California developed a compiler for Apple by that generated the same  as Apple Pascal.

Description
Apple Pascal Operating System introduced a new disk format. Instead of dividing the disk into 256-byte sectors as in DOS 3.2, Apple Pascal divides it into "blocks" of 512 bytes each. The p-System also introduced a different method for saving and retrieving files. Under Apple DOS, files were saved to any available sector that the OS could find, regardless of location. Over time, this could lead to, slowing access to the disk. Apple Pascal attempted to rectify this by saving only to consecutive blocks on the disk.

Other innovations introduced in the file system included the introduction of a feature. Previously only a filename, basic type, and size would be shown. Disks could also be named for the first time.

Limitations of the p-System included new restrictions on the naming of files. Writing files only on consecutive blocks also created problems, because over time free space tended to become too fragmented to store new files. A utility called Krunch was included in the package to consolidate free space.

The biggest problem with the Apple Pascal system was that it was too big to fit on one floppy disk. This meant that on a system with only one floppy disk drive, frequent disk swapping was needed. A system needed at least two disk drives in order to use the operating system properly.

Articles

 * Pascal Syntax Poster by Jef Raskin at Pascal Central (2004-10-08, archived 2004-10-13)
 * The History of Apple’s Pascal “Syntax” Poster, 1979-80 by Lucas Wagner and Jef Raskin at VintageComputer.ca (2018-09-18)

Books

 * Apple II: Apple Pascal Language Reference Manual (PDF), Apple Computer. 1980.