BASIC

The Commodore 64 BASIC on which 10 PRINT runs is a Microsoft product and a descendant of Altair BASIC, although the first step for achieving this BASIC was creating a version for the Commodore 64's chip, the 6502. (The Altair used the Intel 8080, which had a different instruction set.) The task of developing a 6502 version of Microsoft BASIC was undertaken in 1976 and fell mainly to Richard Weiland. When a user types "A" in response to the startup question "MEMORY SIZE?", the version of Microsoft 6502 BASIC that was licensed to Ohio Scientific replies "WRITTEN BY RICHARD W. WEILAND." Version 1.1 for the KIM and subsequent versions declares "WRITTEN BY WEILAND & GATES." But the first version of Microsoft's 6502 BASIC that made its way into a shipping system, in 1977, was a version for Commodore -- not for the Commodore 64, but for their first computer, the Personal Electronic Transactor or PET.

The BASIC included with the Commodore PET was very similar to Commodore BASIC 2 for the Commodore CBM and the BASICs included on the VIC-20 and Commodore 64. Other aspects of Commodore computers, such as the PETSCII character set, are similar across models as well. For these reasons, 10 PRINT will run without modification on a Commodore PET or a VIC-20. The only thing suggesting that this should be called a Commodore 64 program is the presence of 10 PRINT variants in a Commodore 64 manual and a later magazine.

Versions of Microsoft's 6502 BASIC were used not only on the PET and Commodore 64 but also on competing computers: The Apple II series and Atari's 8-bit computers, the Atari 400 and Atari 800. Microsoft certainly benefited from selling the same product to many computer computer companies, but didn't manage to make the usual licensing deal with Commodore. As the founder of Commodore, Jack Tramiel, explained at a 25th anniversary event honoring the Commodore 64, Bill Gates "came to see me. He tried to sell me BASIC. And he told me that I don't have to give him any money. I only have to give him $3 per unit. And I told him that I'm already married." Tramiel told Gates he would pay no more than a $25,000 flat fee for BASIC -- an offer that Microsoft ultimately accepted.