Locomotive BASIC
Locomotive BASIC was a BASIC interpreter for the Amstrad CPC range of computers.
Description
Locomotive BASIC, was one of the best and fastest BASIC implementations of the era. The language benefited both from a clean, well-thought out implementation of the core language by Locomotive, and by the excellent firmware of the CPC, which lent most of its advanced features to the BASIC.
Unlike the competing Commodore 64, it featured a comprehensive graphic capabilities with its PLOT, DRAW, PAPER, INK, PEN, BORDER and (in BASIC 1.1) FILL commands. It had extensive sound commands, granting control of the AY-3-8912 via the firmware's volume and tone envelope system. With the SOUND command, you could select channels, set envelopes, pitch, noise and volume. That was something unmatched by other computers of that era.
Also there was simple interface for memory management, with MEMORY and LOAD commands. The latter allowed for loading of raw screen data, thus providing easy picture showing. Both through this (combined with CALL, PEEK and POKE) and the firmware's RSX system, it was easy to mix BASIC and assembly code, thereby speeding up programs by coding the slowest parts directly in machine code. Many successful programs, including games such as Radzone and applications such as PowerPage, made use of this technique.
With DEF FN, ON variable GOTO and ON variable GOSUB, Locomotive BASIC provided the rudiments of "structured programming", though nowhere near the extent of the PROCedures of BBC BASIC.
All in all, if you compare BASIC interpreters of that era, the Locomotive's seems to be the best 'all-rounder' regarding the combination of speed and complexity, and still some of its features were unmatched by others.
If you are interested in more information about the different versions of the CPC's BASIC and the technical details, you can have a look at the article "Technical information about Locomotive BASIC".
History
The CPC implementation of Locomotive BASIC was developed directly from Locomotive Software's existing Z80 BASIC. The existence of this is cited as one of the reasons Locomotive requested that Amstrad change the CPC's processor from a 6502 to a Z80.
The 464 shipped with BASIC 1.0 on ROM.
The language was revised and debugged for the 664, 6128 and Plus machines to become BASIC 1.1. Changes were minor but significant for the programmer, and included:
- DEC$ bug removed (in BASIC 1.0, it required two opening brackets and was undocumented)
- Better handling of string arguments to RSXs (|DIR,"*.BAS" rather than a$="*.BAS":|DIR,@a$)
- DATA statements can appear anywhere within a line; in BASIC 1.0, they had to be at the end of a line
- FILL command (fill area with solid colour)
- COPYCHR$ function (fetch character from screen)
- Better garbage collection
- Some number-handling bugs removed (e.g. in FOR loops with negative start/end values)
- FRAME (CALL
