Most dialects of BASIC trace their history to the Fourth Edition, and left out more esoteric features like matrix math. In contrast to the Dartmouth compilers, most other BASICs were written as interpreters. This allowed them to run in the limited main memory of early microcomputers. Microsoft BASIC is one example, designed to run in 4 kB of memory. By the early 1980s, tens of millions of home computers were running some variant of the MS interpreter. It became the "de facto" standard for BASIC, which led to the abandonment of the ANSI SBASIC efforts. Kemény and Kurtz later left Dartmouth to develop and promote a version of SBASIC known as True BASIC.