Apple Pascal is an implementation of Pascal for the

Apple II The Apple II (stylized as ) is an 8-bit home computer and one of the world's first highly successful mass-produced microcomputer products. It was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-mold ...

and

Apple III The Apple III (styled as apple ///) is a business-oriented personal computer produced by Apple Computer and released in 1980. Running the Apple SOS operating system, it was intended as the successor to the Apple II series, but was largely consi ...

computer series. It is based on UCSD Pascal. 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 Apple DOS is the family of disk operating systems for the Apple II series of microcomputers from late 1978 through early 1983. It was superseded by ProDOS in 1983. Apple DOS has three major releases: DOS 3.1, DOS 3.2, and DOS 3.3; each one of ...

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. A FORTRAN compiler (written by Silicon Valley Software, Sunnyvale California) compiling to the same p-code as Pascal was also available.

Comparison of Pascal OS with DOS 3.2

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

file system fragmentation In computing, file system fragmentation, sometimes called file system aging, is the tendency of a file system to lay out the contents of files non-continuously to allow in-place modification of their contents. It is a special case of data fragmen ...

, 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

timestamp A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolut ...

feature. Previously only a file's name, 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.

Release history

Sources

*
*
*

Notes

External links

The History of Apple's Pascal "Syntax" Poster, 1979-80.

{{Pascal programming language family Pascal Pascal Disk operating systems Pascal programming language family Discontinued operating systems