computer science

Turbo Pascal

Turbo Pascal is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Turbo Pascal rather than just read about it. In short: Turbo Pascal is a software development system that includes a compiler and an integrated development environment (IDE) for the programming language Pascal running on the operating systems CP/M, CP/M-86, and MS-DOS. It was originally developed by Anders Hejlsberg at Borland, and was notable for its very fast compiling.

Key takeaways

Turbo Pascal belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Turbo Pascal to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Turbo Pascal from memory before moving on to harder problems.

Reference excerpt

Turbo Pascal is a software development system that includes a compiler and an integrated development environment (IDE) for the programming language Pascal running on the operating systems CP/M, CP/M-86, and MS-DOS. It was originally developed by Anders Hejlsberg at Borland, and was notable for its very fast compiling. Turbo Pascal, and the later but similar Turbo C, made Borland a leader in PC-based development tools. For versions 6 and 7 (the last two versions), both a lower-priced Turbo Pascal and more expensive Borland Pascal were produced; Borland Pascal was oriented more toward professional software development, with more libraries and standard library source code. The name Borland Pascal is also used more generically for Borland's dialect of the language Pascal, significantly different from Standard Pascal. Borland has released three old versions of Turbo Pascal free of charge because of their historical interest: the original Turbo Pascal (now known as 1.0), and versions 3.02 and 5.5 for DOS, while Borland's French office released version 7.01 on its FTP.

History Philippe Kahn first saw an opportunity for Borland, his newly formed software company, in the field of programming tools. Historically, the vast majority of programmers saw their workflow in terms of the edit/compile/link cycle, with separate tools dedicated to each task. Programmers wrote source code using a text editor; the source code was then compiled into object code (often requiring multiple passes), and a linker combined object code with runtime libraries to produce an executable program. In the early IBM PC market (1981–1983) the major programming tool vendors all made compilers that worked in a similar fashion. For example, the Microsoft Pascal system consisted of two compiler passes and a final linking pass (which could take minutes on systems with only floppy disks for secondary storage, even though programs were very much smaller than they are today). This process was less resource-intensive than the later integrated development environment (IDE). Vendors of software development tools aimed their products at professional developers, and the price for these basic tools plus ancillary tools like profilers ran into the hundreds of dollars. Kahn's idea was to package all these functions in an integrated programming toolkit designed to have much better performance and resource utilization than the usual professional development tools, and charge a low price for a package integrating a custom text editor, compiler, and all functionality needed to produce executable programs. The program was sold by direct mail order for US$49.95, without going through established sales channels (retailers or resellers). The Turbo Pascal compiler was based on the Blue Label Pascal compiler originally produced for the NasSys cassette-based operating system of the Nascom microcomputer in 1981 by Anders Hejlsberg. Borland licensed Hejlsberg's "PolyPascal" compiler core (Poly Data was the name of Hejlsberg's company in Denmark), and added the user interface and editor. Anders Hejlsberg joined the company as an employee and was the architect for all versions of the Turbo Pascal compiler and the first three versions of Borland Delphi. The compiler was first released as Compas Pascal for CP/M, and then released on 20 November 1983 as Turbo Pascal for CP/M (including the Apple II fitted with a Z-80 SoftCard, effectively converting the 6502-based Apple into a CP/M machine, the Commodore 64 with CP/M cartridge, and the later DEC Rainbow), CP/M-86, and DOS machines. On its launch in the United States market, Turbo Pascal retailed for US$49.99, a very low price for a compiler at the time. The integrated Pascal compiler was of good quality compared to other Pascal products of the time. The Turbo name alluded to the speed of compiling and of the executables produced. The edit/compile/run cycle was fast compared to other Pascal implementations because everything related to building the program was stored in RAM, and because it was a one-pass compiler written in assembly language. Compiling was much faster than compilers for other languages (even Borland's own later compilers for C), and other Pascal compilers, and programmer time was also saved since the program could be compiled and run from the IDE. The execution speed of these COM-format programs was a revelation for developers whose only prior experience programming microcomputers was with interpreted BASIC or UCSD Pascal, which compiled to p-code which was then interpreted at runtime. Unlike some other development tools, Turbo Pascal disks had no copy protection. Turbo Pascal came with the "Book License": "You must treat this software just like a book ... [it] may be used by any number of people ... may be freely moved from one computer location to another, so long as there is no possibility of it being used at one location while it's being used at another."

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Turbo Pascal

Start with the simplest possible case. Write down what Turbo Pascal claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Turbo Pascal before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Turbo Pascal ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Turbo Pascal

In research: Turbo Pascal appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Turbo Pascal in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Turbo Pascal is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1983 software, Borland software, CP/M software, so understanding it makes those chapters shorter.
In everyday life: Look for Turbo Pascal outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Turbo Pascal in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Turbo Pascal means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Turbo Pascal out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Turbo Pascal in simple terms?

Why does Turbo Pascal matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Turbo Pascal?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Turbo Pascal.