Features
It was a rather simple but powerful BASIC implementation by the standards of the day, featuring dedicated commands for handling graphics (such as DRAW, PLOT, INK, and PAPER in all versions; plus FILL in v1.1), even allowing the creation of multiple screens, windows, and the like, although the color system and palette handling was awkward. A table giving the numeric codes for the 27 system colors was printed over the built-in 3" disk drive casing on the 664 and later machines. Simple as it was, it did stand out however among other BASICs of the time by offering a timer-based software interrupt mechanism using the EVERY or AFTER commands; this offered a timed repeating or once-off call respectively to the BASIC line number of your choice.
Also, it granted an almost full control over the CPC sound chip, an AY-3-8912 with 3 melodic channels and 1 noise channel (which was also used on late-model ZX Spectrums, as well as the Atari ST and MSX computers, with none of them having such a complete built-in SOUND command). Everything, from selecting a particular channel or a combination of channels, setting envelopes, volume, pitch, noise, and so on could be done with a single SOUND command, with up to 7 parameters. The only thing that could not be done with BASIC was perhaps playing back digital sampled sounds, like in the game RoboCop.
Disk, tape, and file management were managed by BASIC itself, and were usually good enough for simple file management, with commands such as GET, PUT, ERASE, SAVE, MERGE, RUN, CAT, LOAD etc. In fact, during those years, the BASIC supplied as standard with every low-cost home computer also acted as a more or less simple operating system.
Also available were some special commands for memory allocation and handling, like MEMORY and a parametric LOAD command, allowing, for example, to load a file containing "raw" picture data into video memory, causing it to be displayed, with a couple of BASIC instructions. Adding the right memory address(es) as parameter to the commands LOAD or SAVE would allow easy loading of raw uncompressed 17 KB screen pictures. CALLing another address gave a forced system reset (call 0), the famous "Press Any Key" (call &bb18) or for eliminating flicker in animation by allowing you to synchronize with the monitor's raster scan via "sync frame-flyback" (call &bd19); this was given its own dedicated command in Basic 1.1 - FRAME. With PEEK and POKE, CALL provided an interface to assembly language programming from BASIC.
Read more about this topic: Locomotive BASIC
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