Graphics Programming Language

Graphics Programming Language was a language similar to assembly language used internally on the Texas Instruments TI 99/4 computer line, but kept proprietary and undocumented. The BASIC interpreter was written in this language rather than in raw machine code, which contributed to its extreme slowness. When you ran a BASIC program, the TI BASIC tokenized file was interpreted in an interpreter which ran in Graphics Programming Language, which had to in turn be interpreted by a GPL interpreter (it wasn't compiled or assembled to machine language).

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