Category:Sinclair ZX81 BASIC
This programming language may be used to instruct a computer to perform a task.
If you know Sinclair ZX81 BASIC, please write code for some of the tasks not implemented in Sinclair ZX81 BASIC.
Sinclair ZX81 BASIC is the dialect of BASIC resident in ROM on the ZX81 home computer (1981) and compatibles (Timex Sinclair 1000, Lambda 8300, and many others). It was developed by John Grant and Steve Vickers. Around 1.5 million ZX81s and 'official' compatibles were sold, together with a substantial number of clones (unofficial compatibles) manufactured in Brazil, Hong Kong, and elsewhere. Today, ZX81 emulators exist for a wide range of platforms and operating systems.
ZX81 BASIC is almost a subset of ZX Spectrum Basic, but not quite: the exponentiation operator is spelled
** rather than
↑ (mapped to ASCII
^), the jump and subroutine call keywords are spelled
GOSUB rather than
GO TO and
GO SUB, etc. Note also that the ZX81 uses an idiosyncratic (non-ASCII) character set, so that the
CHR$ functions do not return the same values as they would on the Spectrum. Floating point operations, some string handling, and low-resolution graphics are supported; colour, sound, user-defined functions, the
RESTORE keywords, and assorted other features are not.
The ZX81 has no moving parts and only four microchips: the 3.25MHz Z80 CPU, an 8k ROM chip containing the operating system and BASIC, a 1k RAM chip, and an uncommitted logic array. Since there is no separate video chip, the CPU spends about 75% of its time driving the display and only 25% doing everything else. This can, however, be controlled under BASIC using the
FAST blanks the screen and allows the processor to operate at full speed, and
SLOW reverts to the default behaviour. Even
FAST mode can be slower than some other BASIC dialects running on comparable hardware, because ZX81 BASIC has no integer type: all numeric operations have to be done on 40-bit floats using software floating-point routines. If you are used to other popular 8-bit computers, you should expect the ZX81 to feel noticeably slower.
The original machine's 1k of RAM was shared between the display, the system variables and stack, and the user's program and variables. An expansion pack from Sinclair increased the RAM to 16k; other sizes were available from third parties, allowing the ZX81 to be expanded to a theoretical maximum of 56k. The Timex-branded models marketed in North America came with either 2k or 16k, as did many of the clones. Most ZX81 BASIC programs on Rosetta Code will work with the 1k configuration, but unfortunately some of them do require more. The minimum RAM requirement is usually stated in a note to the program: where it is omitted, it can generally be assumed to be 1k.
A PDF version of the manual, ZX81 BASIC Programming by Steve Vickers, is available here.
If you do not have a ZX81 emulator installed on your computer, and your computer is not itself a ZX81 or ZX81 compatible, you can type any of these programs into the JtyOne online ZX81 emulator and see what they do.
Pages in category "Sinclair ZX81 BASIC"
The following 76 pages are in this category, out of 76 total.