QuickBASIC

Microsoft QuickBASIC (also QB or incorrectly, "QBasic", which is a different system) is a descendant of the BASIC programming language that was developed by the Microsoft Corporation for use with the MS-DOS and Mac OS operating system. It is loosely based on GW-BASIC but adds user-defined types, improved programming structures, better graphics and disk support and a compiler in addition to the interpreter. Microsoft marketed QuickBASIC as the introductory level for their BASIC Professional Development System.

Microsoft released the first version of QuickBASIC on August 18, 1985 stored on a single 5.25" floppy disk. Since version 2.0 QuickBASIC contained an Integrated Development Environment (IDE). Users could edit directly in its onscreen text editor.

Although still supported optionally in QuickBASIC line numbers were no longer needed. Program jumps did also work with named labels. Later versions also added control structures such as multi-line conditional statements and loop blocks.

Microsoft's "PC BASIC Compiler" was included for compiling programs into DOS executables. The editor included an interpreter which allowed the programmer to run the program being edited without leaving the editor, as of version 4.0. The interpreter was used to debug a program before creating an executable file. Unfortunately there were some small, subtle differences between the interpreter and the compiler, so that sometimes a program that ran perfectly well in the interpreter would fail after compilation, or would even not compile at all.

The last version of QuickBASIC was version 4.5 (1988), although development of the Microsoft BASIC Professional Development System (PDS) continued until its last release of version 7.1 in October 1990 (at the same time, the QuickBASIC packaging was sliently changed so that the disks use the same compression used for BASIC PDS 7.1.. The PDS version of the IDE was called QuickBASIC Extended (QBX). The successor to QuickBASIC and PDS was Visual Basic for MS-DOS 1.0, provided in Standard and Professional versions. Later versions of Visual Basic did not include DOS versions, as Microsoft concentrated on Windows applications.

A subset of QuickBASIC 4.5, named QBasic, was included with MS-DOS 5 and later versions, replacing the GW-BASIC included with previous versions of MS-DOS. Compared to QuickBASIC, QBasic is limited to an interpreter only, lacks a few functions, can only handle programs of a limited size, and lacks support for separate program modules. Since it lacks a compiler, it cannot be used to produce executable files, although its program source code can still be compiled by a QuickBASIC 4.5, PDS 7.1 or VBDOS 1.0 compiler, if available.