80-Bus News

  

January–March 1982, Volume 1, Issue 1











Page 32 of 55











32

This extra code will cause the old top line to be copied up to the supranormal top line, where you always used to put headings and things, instead of just being discarded as before. The change just after "Copy down screen" causes the clear screen code to clear the top screen as well. The extra code carries a small time penalty, but in most cases this is insignificant. Performing a Clear Screen, or Cursor Home will cause the cursor to return to the beginning of the second line, as before, and not the new top line. Indeed it’s not possible to place the cursor anywhere in the top line, but I’ve never yet found this to be a problem, and the extra code necessary to get it up there just isn’t worth the trouble. It may be just one extra line but it makes quite a difference. Try it, you’1l like it.

Oh, and while you’re playing about with the SYS source, why not change a few things, such as creating a nice friendly sign-on message, and changing the cursor from a bland old underline to a flashing little man, is one of the hoopiest ideas around!

CP/M USER GROUP SOFTWARE

Well lads, one of the reasons that we all spent vast quantities of pennies on CP/M is that there’s nearly 8 Megabytes of virtually free software available, isn’t it? It’s the CP/M user group library, and there’s some really hoopy stuff in there, including assemblers, languages, applications software, utilities by the score, and games, most with full source code. It’s worthwhile getting hold of several of these volumes, but just which ones depend on your own interests.

The early volumes (that is, upto about vol. 32) have in only a few cases heard of lower case, so you can either modify the source code to convert lower case to upper case, or you can try to remember to use upper case only.

Most of the assembler source is in 8080 code, or if it’s for Z80, it rarely uses Zilog mnemonics. In many cases the syntax is for some strange assembler or another, that you probably haven’t got, but that doesn’t always matter, because there’s usually the corresponding .COM file alongside. The later material seems to have standardised on D.R.’s ‘MAC’ macro assembler, which is upwardly compatible with ASM the assembler which is supplied with CP/M.

In common with most commercial software, the clear screen character is 1AH (SUB) and not 0AH (FF) as is used in a Nascom. I’ve got round this by altering SYS so that both characters clear the screen. However, 1AH is -Z which CP/M uses as an end of file character, and this may cause problems, but _I haven’t encountered any in the three years that I’ve been using CP/M, so it’s probably OK.

The CP/M User Group specify that their software mustn’t be sold at a profit, the most that you should pay is the price of the empty disk, plus a small copying charge (which is usually about a pound per volume). The disks are difficult to get hold of on Nascom format disks, except single sided, and four disks per volume costs a fortune, especially if you want all sixty volumes! L.P. Enterpises over at Barking can supply them in Nascom format for 9.20 per volume (inc VAT) plus 3.45 per volume for insurance, postage and packing. Staubig Studio (of 12,Woburn Street, Ampthill, Bedford) can now supply disks in the format used by Gemini G805 (Henelec) single density disk controllers at 8.00 for a volume needing two disks, and 4.50 for some of the early volumes that’1l fit onto one. P & P is an extra 75p for the first 4 disks, and I5p per disk for each extra disk. A catalogue of the disks presently available is 2.50.


This is an OCR’d version of the scanned page and likely contains recognition errors.











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