MCX BASIC is a dialect of the BASIC programming language. MCX BASIC is designed to follow GW-BASIC, which is one of the standard BASICs running on 16-bit computers. During the creation of MCX BASIC, a major effort was made to make the system as flexible and expandable as possible.

MCX BASIC development environment is very similar to that of the Dartmouth Time Sharing System associated with Dartmouth BASIC. It has a command line-based Integrated Development Environment (IDE) system; all program lines must be numbered, all non-numbered lines are considered to be commands in direct mode (i.e., to be executed immediately). The user interface is almost completely command line.

The original BASIC language was designed on May 1, 1964 by John Kemeny and Thomas Kurtz and implemented by a team of Dartmouth College students under their direction. The acronym BASIC comes from the name of an unpublished paper by Thomas Kurtz. BASIC was designed to allow students to write mainframe computer programs for the Dartmouth Time-Sharing System. It was intended specifically for less technical users who did not have or want the mathematical background previously expected. Being able to use a computer to support teaching and research was quite novel at the time.

The language was based on FORTRAN II, with some influences from ALGOL 60 and with additions to make it suitable for timesharing. Initially, BASIC concentrated on supporting straightforward mathematical work, with matrix arithmetic support from its initial implementation as a batch language, and character string functionality being added by 1965.

The designers of the language decided to make the compiler available free of charge so that the language would become widespread. (In the 1960s, software became a chargeable commodity; until then, it was provided without charge as a service with the very expensive computers, usually available only to lease.) They also made it available to high schools in the Hanover area, and put a considerable amount of effort into promoting the language. In the following years, as other dialects of BASIC appeared, Kemeny and Kurtz's original BASIC dialect became known as Dartmouth BASIC.