Apple Pascal is an implementation of Pascal for the

Apple II Apple II ("apple Roman numerals, two", stylized as Apple ][) is a series of microcomputers manufactured by Apple Computer, Inc. from 1977 to 1993. The Apple II (original), original Apple II model, which gave the series its name, was designed ...

and Apple III computer series, 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 disk operating system for the Apple II computers 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 It was superseded by ProDOS in 1983.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 these three releases was foll ...

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 ProDOS is the name of two similar operating systems for the Apple II of personal computer. The original ProDOS, renamed ProDOS 8 in version 1.2, is the last official operating system usable by all 8-bit Apple II computers, and was distributed ...

. 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 In computing, a compiler is a computer program that Translator (computing), translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primaril ...

(written by Silicon Valley Software of

Sunnyvale, California Sunnyvale () is a city located in the Santa Clara Valley in northwestern Santa Clara County, California, United States. Sunnyvale lies along the historic El Camino Real (California), El Camino Real and U.S. Route 101 in California, Highway 1 ...

) compiling to the same

p-code Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (normal ...

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 Computer file, files non-continuously to allow in-place modification of their contents. It is a special case of ...

, 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 absolu ...

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

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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