On top of ALGOL's scalars and arrays, Pascal enables defining complex datatypes and building dynamic and recursive data structures such as lists, trees and graphs.

It was widely used as a teaching language in university-level programming courses in the 1980s, and also used in production settings for writing commercial software during the same period.

This was used by Apple Computer (for the Lisa and Macintosh machines) and Borland in the late 1980s and later developed into Delphi on the Microsoft Windows platform.

The group tasked with maintaining the language had begun the ALGOL X process to identify improvements, calling for submissions.

Wirth and Tony Hoare submitted a conservative set of modifications to add strings and clean up some of the syntax.

Pascal was influenced by the ALGOL W efforts, with the explicit goals of teaching programming in a structured fashion and for the development of system software.

One of the early successes for the language was the introduction of UCSD Pascal, a version that ran on a custom operating system that could be ported to different platforms.

Parts of the original Macintosh operating system were hand-translated into Motorola 68000 assembly language from the Pascal source code.

The second attempt was implemented in a C-like language (Scallop by Max Engeli) and then translated by hand (by R. Schild) to Pascal itself for boot-strapping.

The Multum port was developed – with a view to using Pascal as a systems programming language – by Findlay, Cupples, Cavouras and Davis, working at the Department of Computing Science in Glasgow University.

It offered a source-language diagnostic feature (incorporating profiling, tracing and type-aware formatted postmortem dumps) that was implemented by Findlay and Watt at Glasgow University.

The first Pascal compiler written in North America was constructed at the University of Illinois under Donald B. Gillies for the PDP-11 and generated native machine code.

Turbo Pascal became hugely popular, thanks to an aggressive pricing strategy, having one of the first full-screen IDEs, and very fast turnaround time (just seconds to compile, link, and run).

Around the same time a number of concepts were imported from C to let Pascal programmers use the C-based application programming interface (API) of Microsoft Windows directly.

Pascal-XSC has at various times been ported to Unix (Linux, SunOS, HP-UX, AIX) and Microsoft/IBM (DOS with EMX, OS/2, Windows) operating systems.

It was standard Pascal level-1 (with parameterized array bounds) but the definition allowed alternative keywords and predefined identifiers in French and the language included a few extensions to ease system programming (e.g. an equivalent to lseek).

It includes objects, namespace controls, dynamic arrays, and many other extensions, and generally features the same functionality and type protection as C#.

This capability was included in a number of Pascal extensions and follow-on languages, while others, like Modula-2, expanded the built-in set to cover most machine data types like 16-bit integers.

The packed keyword tells the compiler to use the most efficient method of storage for the structured data types: sets, arrays and records, rather than using one word for each element.

However, the addition of ALGOL-like empty statements in the 1973 Revised Report and later changes to the language in ISO 7185:1983 now allow for optional semicolons in most of these cases.

The precipitating cause was that Hoare wanted to create a Pascal version of the (NAG) Numerical Algorithms Library, which had originally been written in FORTRAN, and found that it was not possible to do so without an extension that would allow array parameters of varying size.

Niklaus Wirth himself referred to the 1974 language as "the Standard", for example, to differentiate it from the machine specific features of the CDC 6000 compiler.

[41] Niklaus Wirth's Zürich version of Pascal was issued outside ETH in two basic forms: the CDC 6000 compiler source, and a porting kit called Pascal-P system.

For example, procedures and functions used as parameters, undiscriminated variant records, packing, dispose, interprocedural gotos and other features of the full compiler were omitted.

UCSD Pascal, under Professor Kenneth Bowles, was based on the Pascal-P2 kit, and consequently shared several of the Pascal-P language restrictions.

In the early 1990s, Alan Burns and Geoff Davies developed Pascal-FC, an extension to Pl/0 (from the Niklaus' book Algorithms + Data Structures = Programs).

Several constructs were added to use Pascal-FC as a teaching tool for Concurrent Programming (such as semaphores, monitors, channels, remote-invocation and resources).

Software products (compilers, and IDE/Rapid Application Development (RAD)) in this category: Pascal generated a wide variety of responses in the computing community, both critical and complimentary.

Kernighan also criticized the unpredictable order of evaluation of Boolean expressions, poor library support, and lack of static variables, and raised a number of smaller issues.

It supports variable-length strings, variable initialization, separate compilation, short-circuit Boolean operators, and default (otherwise) clauses for case statements.