PLOGO(ID:5892/)Logo rewritten in Pascalfor Pascal Logo LOGO written in Pascal for the TI 94 Related languages
References: Around 1977-1978, Gary Drescher and someone else whose name escapes me at the moment wrote a version of Logo in Pascal, as part of a project with Texas Instruments, for the TI 99/4 Home Computer, because Pascal was the only high-level language supported. They finished it and compiled it, and it produced something like a 300Kb program. That doesn't sound like much, but considering that the TI 99/4 in its most burly configuration had 32Kb, it was tremendous. So, the Logo Lab hired Edward Hardebeck to be a human compiler for the TI 99/4. The machine had twice as many registers as a PDP-11, but only half as many addressing modes, so it wasn't possible to implement a PUSH/POP stack for function call and return, or for data push and pop, in a single instruction. Furthermore, all but 256 bytes of the memory was accessed off-chip through a 12-clock-cycle interface. In other words, most of the time, the machine ran at 1/12th of its designed speed, which was pretty slow in the first place. The machine had register windows, which is much like current RISC processors, and the 256 bytes were intended for those. Ed implemented some common subroutines in part of the 256 bytes, and used the rest for registers. Anyway, the machine had a SPRITE chip, which was the result of a collaboration between Danny Hillis and TI. The idea of a SPRITE chip was Danny's bachelor's thesis... The idea of getting out Logo on such a machine, and the possibility of having the first microcomputer version of Logo available for use in real schools, pushed everyone on. TI had a couple of programmers assigned to the project in Texas, and they did the final work of shoehorning everything in to fit into the 99/4 -- we're talking about a few hundred bytes here and there total. It must have been grueling work. For example, they shortened all abbreviations to two letters -- memory was that tight. |