Turbo Pascal - CP/M and DOS Versions

CP/M and DOS Versions

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 November 20, 1983 as Turbo Pascal for CP/M (including Apple II computers fitted with Z-80 SoftCards and the DEC Rainbow), CP/M-86, and MS-DOS machines. On its launch in the United States market, Turbo Pascal retailed for USD49.99, 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 compilation 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. Compilation was very quick compared to that for other languages (even Borland's own later compilers for C), and programmer time was also saved since the program could be compiled and run from the IDE. The speed of these COM executable files was a revelation for developers whose only prior experience programming microcomputers was with interpreted BASIC or UCSD Pascal, which compiled to p-code.

The program required a computer running MS-DOS, CP/M, or CP/M-86 with 64kB of memory and a floppy drive, typically an Apple ][ with a CP/M card and a single 140kB floppy drive, or a PC with a 160kB drive. The installer, lister, and compiler with its IDE, along with a demonstration program (in the form of source code for a simple spreadsheet called MicroCalc), would fit on a single floppy disc. If the demonstration program was deleted, there was sufficient space for the typical user's source code and compiled executable. As it was common at the time for users to have only one floppy drive (and no hard drive), it was a great convenience to be able to fit the compiler and the program being written on a single disc.

Bill Gates saw the success of Turbo Pascal "in very personal terms, and 'couldn't understand why stuff was so slow. He would bring in poor Greg Whitten and yell at him for half an hour.' He couldn't understand why Kahn had been able to beat an established competitor like Microsoft."

The IDE was very advanced for its day, when computing resources on the IBM PC were very limited (IBM's PC design having been "prudently" constrained so that its performance would not compete with IBM's profitable enterprise products). The IDE was simple and intuitive, and had a well-organized system of menus. Early versions of the editor used WordStar key functions, which was the de facto standard at the time. Later versions of the IDE, designed for PCs with more disk space and memory, could display the definitions of the keywords of the language by putting the cursor over a keyword and pressing the F1 key. The definitions also frequently included example code.

Versions 2 and 3 were improved versions of the same, basic all-in-one system, working in memory and producing .COM executable files for DOS and CP/M, and equivalent .CMD executables for CP/M-86 (not the same as .CMD batch files used in 32-bit Microsoft Windows).

The .COM format let programmers write Terminate and Stay Resident programs, small utilities that stayed in memory and let the computer do other tasks, something very popular in the days before multitasking systems such as Microsoft Windows. Borland itself produced a small application suite called SideKick that was a TSR letting the user keep a diary, notes, and so forth.

Versions 1 to 3 were incremental improvements to the original Turbo Pascal. Version 4, released in 1987, was a major rewrite of the whole system, and versions 5 to 7 were incremental improvements and expansions. The compiler generated executables in .EXE format under DOS, rather than the simpler but more restricted .COM executables. The by-then obsolete CP/M and CP/M-86 operating system versions were dropped. Version 4 also introduced units, and a full-screen text user interface with pull-down menus; earlier versions had a text-based menu screen and a separate full-screen editor. (Microsoft Windows did not exist when the first version was released, and even mice were rare.)

Version 5.0 introduced the Borland blue screen, used by Borland's DOS compilers until the end of this product line in the mid-1990s.

Later versions came in two packages with the same version number: a less expensive "Turbo" package, and a "Borland" package with enhanced capabilities and more add-ons.

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