Editing ZX Spectrum (section)

=== Firmware ===
[[File:ZXspectrum mb.jpg|thumb|48K motherboard (Issue 3B: 1983, heat sink removed)]]
The machine's [[Sinclair BASIC]] interpreter is stored in 16&nbsp;KiB ROM, along with essential system routines. The ROM code, responsible for tasks such as [[floating point]] calculations and [[parser|expression parsing]], exhibited significant similarities to ZX81, although a few outdated routines remained in the Spectrum ROM.{{sfn|Nash|1984|p=217}} The Spectrum's keyboard is imprinted with BASIC keywords. To input a command in BASIC, many keywords require a single keyboard stroke. Other keywords require a change of keyboard mode by a few keystrokes.<ref name="Vickers-2">{{Cite book |last= Vickers |first= Steven |title= Sinclair ZX Spectrum BASIC Programming |url= http://www.worldofspectrum.org/ZXBasicManual/ |access-date= 19 September 2006 |year= 1982 |publisher= [[Sinclair Research Ltd]] |chapter= Basic programming concepts |chapter-url= http://www.worldofspectrum.org/ZXBasicManual/zxmanchap2.html |url-status= live |archive-url= https://web.archive.org/web/20060924115058/http://www.worldofspectrum.org/ZXBasicManual/ |archive-date= 24 September 2006 }}</ref>

The BASIC interpreter is derived from the one used on the [[ZX81]]. A BASIC program for ZX81 can be entered into a ZX Spectrum with minimal modifications. However, Spectrum BASIC introduced numerous additional features, enhancing its usability. The [[ZX Spectrum character set]] was expanded compared to that of the ZX81, which lacked lowercase letters. Spectrum BASIC incorporated extra keywords for better graphics and sound functionality, and support for multi-statement lines was added. The built-in ROM tape modulation software routines for cassette data storage enable data transfers at an average speed of 171 [[bit rate|bits per second]] (bit/s), with a theoretical peak speed of 256 bit/s. The tape modulation is significantly more advanced than the ZX81, with approximately four times faster average speeds.<ref name="myprius">{{cite web|url=http://www.myprius.co.za/tape_storage.htm|title=Tape Data Storage|access-date=19 August 2012|url-status=live|archive-url=https://web.archive.org/web/20120415055937/http://www.myprius.co.za/tape_storage.htm|archive-date=15 April 2012}}</ref>