Ian Logan – Timex/Sinclair Computers

When Ian Logan was working at Sinclair, he met Scott McCourt. Scott asked Ian for help – to go over to the US and write software for them.

“They wanted to add new commands to the Spectrum,” says Ian. “The machine was a 1981 design and requirements for a 1983 computer have evolved since then. They were going to have to redo the Spectrum printed-circuit board for the TS2000 to satisfy US FCC regulations and to make it compatible with the NTSC TV standard. So, while they were about it, they decided to produce an enhanced version, with extra commands.”

During his two weeks stay with Timex, Ian showed them how to add new commands and routines. He extended the syntax checking and corrected some of the small bugs in the Spectrum’s own ROM.

Articles (24)

Title	Author(s)	Publication	Date
8K ROM Monitor Routines Continuation of article from prior issue examining the 8K ROM.		Syntax	October 1981
A Report on the Spectrum The Spectrum is a ZX81 that has been developed by adding a hi-resolution display, color board, improved cassette interface and...		Syntax	September 1982
All about ROMs In Understanding Your ZX-81 ROM, by Ian Logan, the reader doesn’t have to contend with an update from the Sinclair...		Timex Sinclair User	July 1983
An Introduction to Expression Evaluation In the Sinclair 8K ROM program of the ZX80/81 the “expression evaluator” is to be found at 0F55-111Bh (improved 8K...		SYNC	May/June 1982
An Introduction to Machine Code The ZX80/1 microcomputer system as supplied by Sinclair Research is capable of being programmed in two different languages, i.e., Basic...		SYNC	November/December 1981
An Introduction to Machine Code How to start using machine code on the ZX80/81.		SYNC	Special Issue 1982
Auto-Display-Changing How Is It Done? A series of articles.		SYNC	May/June 1981
Clarification of Bytes Remaining Ian Logan’s 8K Bytes Remaining program, Dec. 81, uses function keywords for all input except E, the numbers, and the...		Syntax	January 1982
Dear Editor ZX-Microfair in London; Microace 8K ROM has bugs; Microace regulator; floating point in 8K ROM.		Syntax	November 1981
How to Produce a Display File Using Machine Code In the ZX80 the display file is the part of the RAM which holds the next picture to be shown....		SYNC	March/April 1981
Keyboard Scanning from Machine Code Explains how to scan the ZX80/81 keyboard from machine code in SLOW mode using the LAST K system variable (16421-16422)....	Ian Logan	Syntax	July 1982
Logan’s Run… Interview with Ian Logan, author of several Sinclair ROM disassembly books.		Popular Computing Weekly	22-28 September 1983
Machine Code Print Routine Machine language (ML) permits you to print characters anywhere on the screen. Harness the ZX80’s own print routine with RST...		Syntax	September 1981
Machine Code Programming — Understanding the Stack Often when writing machine code (MC) programs, it’s useful to keep the MC above RAMTOP. But few people understand how...		Syntax	August 1982
Screen Scrolling This article shows how a routine can he written and entered into a ZX80 that enables the user to SCROLL...		SYNC	July/August 1981
Software Reviews: Moi Othello and The Fast One Reviews of two ZX81 programs from UK publishers. Moi Othello (Mine of Information, £19 US) is an advanced Othello implementation...	Ian Logan	Syntax	April 1982
The Flags of the 8K ROM Program The ZX81 manual states that the three system variables FLAGS, FLAGX and CDFLAG hold various flags to control the BASIC...		Syntax	February 1982
The PEEK Function and the POKE Command This article returns to Basic to discuss the PEEK function and the POKE command. Since the 8K ROM is now...		SYNC	September/October 1981
The ZX81 Companion Bob Maunder’s new book is very different from The ZX80 Companion. It aims to appeal to every ZX81 owner, but...		Syntax	November 1981
Timex v Spectrum Ian Logan looks at the US answer to the Spectrum – the Timex-Sinclair 2068.		Popular Computing Weekly	October 13-19, 1983
Understanding Floating-point Arithmetic, Part 2 Describes the workings on the ‘third language’ of the 8K ROM – the CALCULATOR LANGUAGE – that is used to...		SYNC	March/April 1982
Understanding Floating-point Arithmetic, Part 3 In this article on floating-point arithmetic, we will consider the algorithms that are used in the 8K ROM program to...		SYNC	July/August 1982
Understanding Floating-point Arithmetic: Part 1 The aim of this article is to give the reader some insight into the complex world of floating-point arithmetic. Since...		SYNC	January/February 1982
Writing Game Programs How do you start writing game programs?		Syntax	July 1981

Products (1)

Title	Company
Reversi A machine code Othello playing program. Played on an 8 x 8 board with full screen display; allows only legal...	Melbourne House Publishers

Books (6)

Title	Author(s)	Date
The Complete Spectrum ROM Disassembly American readers found this book invaluable in understanding the Timex/Sinclair 2068 ROM.	Ian Logan, Frank O'Hara	1983
The Complete Timex TS1000/Sinclair ZX81 ROM Disassembly Includes Part A: 0000H-0F54H & Part B: 0F55H – 1DFFH.	Ian Logan; Frank O'Hara	1982
The ZX80 Companion Covers BASIC, hardware and software, with detailed explanation of the monitor, routines and entry points.	Bob Maunder; Terry Trotter; Ian Logan	1980
The ZX81 Companion Assists ZX81 users in four application areas: graphics, information retrieval, education and games. The book includes scores of fully documented...	Robert Maunder; Terry Trotter; Ian Logan	1981
TS2000 Programmer’s Reference Guide Melbourne House expected to publish this book, based on Ian Logan’s Understanding Your Spectrum, in December 1983.	Ian Logan	December 1983
Understanding Your ZX81 ROM Illustrates all the facilities of the ZX81/TS1000 monitor, how it works, and how you can use it in your own...	Ian Logan	1981