Tiny Logo

ZX Computing

THE ZX81 SOFT SELECTION Nick Pearce casts his eye over some new releases. TINY LOGO Computer Magic Tiny LOGO is an implementation for the ZX81 of the popular Massachusetts Institute of Technology programming language called LOGO, adaptations of which are now available for many personal computers. The principles of LOGO were described by Tim Hartnell back in the April/May issue of ZX Computing and a LOGO translation program for the Spectrum, "Slogo" by David Nowotnik was presented in the following three issues. Briefly, LOGO was designed to provide an introduction to computer programming with particular emphasis on simplicity and the development of logical thinking. The most familiar aspect of LOGO is 'turtle graphics', whereby a 'turtle' on the screen moves according to the programmer's commands. As it travels, it leaves behind a trail, and in this way pictures can be created by telling the turtle where to go. The turtle in Tiny LOGO is a pixel. This caused me some difficulty, since there is no indication on screen of the direction the turtle is facing. The trail left by the turtle is also in pixels, so picture resolution is limited to the ZX81's 63 x 43 screen pixels. Another problem is that the program runs rather slowly, there is a pause during which the screen is blank in between executing each command, and I think the slowness would be frustrating were the program to be used for extended periods. The program is written entirely in BASIC, ideally a LOGO translation program should be written in machine code to give a faster operating speed. In other respects the program is very good with a comprehensive set of turtle graphics commands as well as more advanced procedures (the language works by defining sequences of steps called procedures which are then called and executed). There is an editing facility so that procedures can be easily modified or corrected. These are kept in an area called the "workspace", which can contain up to fifteen procedures. Procedures, as well as screen displays, can be saved on cassette. There is no shorthand in Tiny LOGO, all commands have to be typed in full, which can be somewhat time consuming. The cassette comes complete with a well-written instruction booklet which explains the language by means of short example programs and contains two useful appendices - a command summary table and an explanation of the program's error reports. LOGO has been described as the language of the '80s. It is beginning to be used in school classrooms, and whilst Tiny LOGO on the ZX81 has some shortcomings, it would nevertheless be a worthwhile investment for children with access to a 16K ZX81 just starting their computer education. Tiny LOGO by Computer Magic is published by International Publishing and Software inc. [redacted].