Microsoft QuickBASIC compiler

Microsoft QuickBASIC (often shortened, correctly, to QB, or incorrectly, to QBASIC) is a descendant of the BASIC programming language that was developed by the Microsoft Corporation for use with the MSDOS Operating System. It was loosely based on Microsoft GW-BASIC but in addition provided user-defined types, improved programming structures, better graphics and disk support and a compiler rather than an interpreter. Microsoft sold QuickBASIC as a commercial development suite.

Microsoft released the first version of QuickBASIC on August 18, 1985 stored on a single 5.25" floppy disk. QuickBASIC came with a markedly different Integrated Design Environment (IDE) from the one supplied with previous versions of BASIC. Line numbers were no longer needed since users could insert and remove lines directly via an onscreen text editor.

Microsoft's "PC BASIC Compiler" was included which could be used to compile programs into DOS executables. The editor also had an interpreter built in which would run the program without leaving the editor at all, and could be used to debug the program before creating an executable file.

The last version of QuickBASIC was 4.5 although there was continued development of the Professional Development System (PDS), the last release of which was version 7.1. The PDS version was also sometimes called QuickBASIC Extended. The successor to QuickBASIC and PDS was Visual Basic 1.0 which came in incompatible versions for DOS and Windows. Later versions of Visual Basic did not include DOS versions as Microsoft wanted developers to concentrate on Windows applications.

A replacement for GW-BASIC, based on QuickBASIC 4.5 was included with MS-DOS 5 and later versions. This is called QBASIC. Compared to QuickBASIC, it is limited as it lacks a few functions, can only handle programs of a limited size, lacks support for separate modules, and is an interpreter only. It cannot be used to produce executable files directly although programs developed using it can still be compiled by a QuickBASIC 4.5, PDS 7.1 or VBDOS 1.0 compiler, if one is available.