Microsoft QuickBASIC (also QB or incorrectly, "QBasic", which is a different system) is an Integrated Development Environment (or IDE) and compiler for the BASIC programming language that was developed by Microsoft. QuickBASIC runs mainly on DOS, though there was a short-lived version for Mac OS. 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 on a single 5.25" 360kB floppy disk. QuickBASIC version 2.0 and later contained an Integrated Development Environment (IDE), allowing users to edit directly in its on-screen text editor.
Although still supported in QuickBASIC, line numbers became optional. Program jumps also worked with named labels. Later versions also added control structures, such as multiline conditional statements and loop blocks.
Microsoft's "PC BASIC Compiler" was included for compiling programs into DOS executables. Beginning with version 4.0, the editor included an interpreter that allowed the programmer to run the program without leaving the editor. The interpreter was used to debug a program before creating an executable file. Unfortunately, there were some subtle differences between the interpreter and the compiler, so that sometimes a program that ran correctly in the interpreter would fail after compilation, or 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 silently changed so that the disks used the same compression used for BASIC PDS 7.1. The Basic PDS 7.x version of the IDE was called QuickBASIC Extended (QBX), and it only ran on DOS, unlike the rest of Basic PDS 7.x, which also ran on OS/2. The successor to QuickBASIC and Basic PDS was Visual Basic for MS-DOS 1.0, shipped 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.x or VBDOS 1.0 compiler, if available.
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