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Microsoft BASIC was the foundation product of the Microsoft company. It first appeared in 1975 as Altair BASIC, which was the first BASIC (and indeed the first high level programming language) available for the MITS Altair 8800 hobbyist microcomputer.

The Altair BASIC interpreter was developed by Microsoft founders Paul Allen and Bill Gates with help from Monte Davidoff, using a self made Intel 8080 software simulator running on a PDP-10 minicomputer. The dialect of BASIC was similar to Digital Equipment Corporation interpreters, especially in string operations, which varied between BASIC implementations. BASIC used dynamically allocated strings which stored their size, a feature not common in C or C++ until the Standard Template Library of the 1990s. Many of these string operations remain today in the .NET Framework. Early BASIC only supported single letter and digit names, but Microsoft BASIC supported long variable names. The runtime symbol table however used a linear search, so that a program which used many distinct variables would run much slower than a program which used a single array for all its variables.

It was delivered on paper tape and in its original version took 4 KiB of memory. The extended 8 KiB version was then generalized into BASIC-80 (8080/85, Z80), and ported into BASIC-68 (6800), BASIC-69 (6809), and MOS Technology 6502-BASIC (unfortunately spilling over to 9 KiB, in an era when 8 KiB ROM chips were standard), as well as the 16-bit BASIC-86 (8086/88). It was ideal for ROM-based computers since it did not require an editor (each line requires a number), nor a disk drive to store object code or linked executable. It was less sophisticated than industrial desktop computers such as the HP 9830 which had dedicated keys to load, store, and keys for editing within a line and debugging, but personal computers, in contrast, didn't cost $7,000.

After the initial success of Altair BASIC, Microsoft BASIC became the basis for a lucrative software licensing business, being ported to the majority of the numerous home and personal computers of the 1970s and especially the 1980s, and extended along the way. Contrary to the original Altair BASIC, most home computer BASICs were resident in ROM, and thus were available on the machines at power-on in the form of the characteristic "READY."-prompt. Hence, Microsoft's and other variants of BASIC constituted a significant and visible part of many home computers' rudimentary operating systems.

Microsoft BASIC (BASICA.EXE, GWBASIC.EXE, QBASIC.EXE) is no longer found on distributions of Windows or DOS, however, it can be downloaded from various Internet sites, and archives of DOS versions or old DOS disks which will still run on Pentium class Windows XP machines. The latest version of BASIC is VB.NET which incorporates most of the features of C++ and C# and can be used to develop web forms, windows forms, and server-based applications. Most .NET code samples are presented in VB.NET as well as C#, and VB.NET continues to be favored by former Visual Basic programmers.

• Altair BASIC (MITS Altair and other S-100 computers)
• Amiga BASIC (Commodore Amiga family)
• Applesoft BASIC (Apple II family)
• Atari Microsoft BASIC I and II (Atari 8-bit family)
• BASICA ("BASIC Advanced") (PC-DOS, on IBM PC)
• Color BASIC (TRS-80 Color Computer)
• Commodore BASIC (Commodore 8-bit family, incl C64)
• Extended Color BASIC (TRS-80 Color Computer and Dragon 32/64)
• IBM Cassette BASIC (PC-DOS, on original IBM PC)
• Galaksija BASIC (Galaksija home computer)
• GW-BASIC (BASICA for MS-DOS, on PC compatibles)
• Microsoft Level III BASIC (Tandy/Radio-Shack TRS-80)
• MBASIC (CP/M, on 8080/85 and Z80 based computers)
• MS BASIC for Macintosh (Mac OS on Apple Macintosh)
• MSX BASIC (MSX standard home computers)
• N88-BASIC (NEC PC8801/9801)
• QBasic (PC-DOS/MS-DOS on IBM PC and compatibles)
• QuickBASIC (PC-DOS/MS-DOS on IBM PC and compatibles))
• TRS-80 Level II BASIC (Tandy/Radio-Shack TRS-80)
• Visual Basic (PC-DOS/MS-DOS/MS Windows on IBM PC and compatibles)
• WordBasic (pre-VBA) (MS Windows)
• HP2640 HP2647 Programmable Terminal with AGL graphics extensions
• FreeBASIC - a free clone of the QuickBasic system.

• Microsoft® BASIC Version Information – At the Old Software Information website