QBasic
The "Opening" Screen in Qbasic 4.5
QBASIC (Quick Beginner's All-Purpose Symbolic Instruction Code), or QBasic, is a variant of the BASIC programming language. It has no compiler, and the code is executed (interpreted) at runtime in the integrated development environment (IDE). It was released as of MS-DOS 3.0, and was shipped together with MS-DOS 5.0 and higher, including Windows 95. It was soon succeeded by QuickBASIC 4.5, 7.1, and VBDOS 1.0, which included compilers as well as interpreters.
Microsoft stopped shipping QBasic with later versions of Windows (Windows 98 users for example will find it in the tools/oldmsdos/ directory of the W98 CD-ROM) and it is no longer available. QBasic provided a state-of-the-art IDE (for its time), including a debugger with features such as on-the-fly expression evaluation and code modification that were still relatively unusual in 2003, more than ten years later.
QBasic was based on Microsoft's Professional Development System Basic, also known as PDS Basic or simply PDS. PDS Basic was followed by VBDOS 1.0 and its language engine was likely the foundation for Microsoft's market-leading Visual Basic for Windows.
QBasic has also made its way into several third-party tools, such as the XBasic compiler and PowerBasic series of compilers. QBasic was also the subject of Beginning Programming For Dummies.
Syntax
Unlike early versions of BASIC, QBasic was a structured programming language, supporting constructs such as named subroutines and while loops. Line numbers, a concept often associated with BASIC, were supported for compatibility, but were not necessary and not considered good form. QBasic also has support for structures (TYPEs).