Full BASIC, sometimes known as Standard BASIC or ANSI BASIC, is an international standard defining a dialect of the BASIC programming language. It was developed by the American National Standards Institute (ANSI) X3.60 group in partnership with the European ECMA. It describes an advanced version of BASIC with many features including structured programming, matrix math, input/output for file handling, and many other options.

ANSI's BASIC standardization was a two-stage process. The first, carried out as Minimal BASIC starting in 1974, was an effort to clearly define and standardize the original Dartmouth BASIC language so it could be correctly implemented on different platforms. After its release in late 1977, attention turned to Full BASIC which would be based on the more powerful Structured BASIC being developed at Dartmouth College. The complexity of the system and the many additions promoted by members of the standards committee led to the effort bogging down and the first draft standard was not ready until 1986, four years late.

The standard was ratified on 26 June 1986 as ECMA-116, in January 1987 as ANSI X3.113-1987, in 1991 as ISO/IEC 10279:1991 and last reviewed and confirmed in 2024. It was completely ignored; the microcomputer revolution had occurred while the specification was being argued over, and by the early-1980s Microsoft BASIC running on tens of millions of home computers had already come and gone. Watching the process drag on, the Dartmouth participants left to produce True BASIC based on parts of the standard, but this saw little use. De facto standards like Microsoft's dominated the market and formed the basis for newer languages like Microsoft Visual Basic which incorporated similar concepts.^{[citation needed]}

The introduction of Dartmouth BASIC in 1964 combined a number of emerging concepts in the computer field, including timesharing and direct interaction with the user, known at the time as a "conversational interface". General Electric, who supplied the GE 235 mainframe computer it ran on, used a modified version of Dartmouth's system to start a service bureau which would eventually evolve into the GEnie online service. Many other companies, Tymshare and CompuServe notable among them, quickly introduced hosted BASIC services of their own, following the Dartmouth model.

In 1968, Hewlett-Packard (HP) introduced the HP 2000 series minicomputers, which offered the same features of the earlier mainframe systems in a rack-mount system that could be configured in a complete form for around $100,000 (equivalent to $925,837 in 2025). Their HP Time-Shared BASIC had a number of differences from Dartmouth, and these were soon copied by other mini vendors like Data General. One holdout was Digital Equipment Corporation (DEC), who did not introduce a BASIC of their own design until 1972. This version, BASIC-PLUS was different from either the HP or Dartmouth dialects. By the early 1970s there were three major dialects and dozens of minor variations being used in the market.

In January 1974 a new group formed under the ANSI umbrella to define a single standard BASIC. The Dartmouth team formed a core part of the group. Dartmouth was working on a greatly expanded version of BASIC known as Structured BASIC (SBASIC) which became the basis for ANSI. At the time, few other dialects supported its many new features. The group decided that a complete standard based on SBASIC would take some time to agree on, so the ANSI BASIC effort was split into two milestones. The first, Minimal BASIC, would produce a standard that included only the most basic features that would be required of any implementation. Even long-supported features from Dartmouth like matrix math would be left out. The draft standard for Minimal BASIC was released in January 1976, the final draft in July 1977, and it was ratified that December. Arthur Luehrmann, a physicist from Dartmouth College who was a proponent of BASIC and part of the ANSI group later stated:

"X3J2's first few years were spent (in hindsight, some might say 'wasted') on standardizing what amounts to the original 1964 Dartmouth Basic... Minimal Basic was more a toy than an actual language."

The group then turned their attention to Full BASIC. By this time the microcomputer revolution was in full flight, and millions of machines running Microsoft BASIC or a similar BASIC were entering the market. In spite of this, none of the participants were microcomputer vendors or suppliers. Instead, the participants remained mainframe vendors like IBM, Control Data and General Electric, minicomputer vendors like Digital Equipment Corporation (DEC), Data General and Wang Laboratories, and other very large companies like 3M, American Express and Kodak.