64

PROGRAM PITSTOP


Your Sinclair, June 1992





CRAIG BROADBENT has recently discovered a peculiar penchant for


Macaroni Cheese; luckily this hasn't stopped him from typing in


those cheesy listings.








First of all I'd like to say how impressed I was by the amount of mail


I got this month - well done to all involved. And keep it up! This


month's lucky winner is Paul Wardle for his lovely print routines. As


for the rest of you, don't despair - there was so much good stuff sent


in that some of it may well see the glossy pages of YS in a future


issue. I actually picked out three programs for this month's pitstop


but there was absolutely no way they'd fit in. So you'd better tune in


next month hadn't you?








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42 AND 64


by Paul Wardle





What's so special about 42 And 64 then? Well, as any fule kno, 42 is


the answer to Life, the Universe and Everything. 64 is a somewhat


inferior Speccy rival whose manufacturers were eventually forced to


start making 16-bit computers in order to make a living. More to the


point though, 42 And 64 are two lovely, smashing, great etc. print


routines that enable you to print text in 42 columns, 64 columns or


Tasword.





The machine code listing is the one that does all the work. For 42 it


takes a string, chops two columns out of each character and prints the


remainder whilst attempting to reconfigure the attributes as it does


so. (Although, obviously, it can't change the position of the


attribute grid.) Paul also refers me back to a similar routine in


YS.29 which was written by the then presenter of Pitstop - David


McCandless. Paul goes on to say that 42 is dead useful for tables and


stuff because it doesn't do proportional type and the caps are printed


the same width as lower case letters.





64 works in a slightly different way, it has a whole new 4-pixel wide


character set contained within the Hex. Also, both routines can be


printed on the bottom two lines without any of that funny #1 business.








How it works





It's so simple! All you have to do is type in LET Z$="a sentence" and


then RANDOMIZE USR 60000 for both routines. [The 42-char version on


PR_42_64.TAP starts at 63234, as I happened to have one already typed


up which had been altered to work from that address. JimG] If you're


really fussy you can put co-ordinates in as well, in the form:


LET Z$ = CHR$ 22 + [y co-ord] + [x co-ord] + "a sentence"


Alternatively, you could set up a function to do the donkey work of


fitting the co-ordinates in; just take a look at the demo listing for


more details.





For 42, the screen is 42 wide by 24 deep; and for 64 it's 64 across by


24 down. You can also insert a CHR$ 13 to do the same as an ENTER. And


remember, you don't affect the AT position by clearing the screen.








Techy bits





Paul has also sent in a run-down of the code bits. 42 is split into


four parts ...


63234 - 63326: Main handling routine, checks for control codes and


prints the string on the screen.


63327 - 63545: This routine forms the new 6-bit wide characters and


alters the colours to match the text. The y,x co-ordinates and eight


bytes of workspace are located at the end of this chunk.


63546 - 63641: The data showing which columns to chop out of each


character.


63642 - 63689: The completely redefined characters %, &, 0, T, Y and


(c). These just look daft with columns cut out.





64 is split into three similar parts:


60000 - 60092: Handling routine, same as the one for 42.


60093 - 60229: Printing routine accesses the new 4-bit wide character


set and alters the colours. Contains the y,x co-ordinates at the end.


60230 - 60613: The data containing the new character set. To save


memory, each byte contains two characters. Characters can be retrieved


using the formula Address = Base + 8 * (Code-32)/2. The remainder


following the division gives the position of the character within the


single byte, found by examining the carry flag.








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EGGS





Well, I can see the page number looming in front of me. It's time to


pack up my tools and lock up the Pitstop for another month. But what


an apple pie of a column we've had this month, eh? What's more, next


month's is going to be just as full. And how would you like to see


the same amount the month after that? You would? Good, just send in


those programs and I'll see what I can do. The name's CB and the address


is Program Pitstop, Your Sinclair, 30 Monmouth Street, Bath, Avon BA1 2BW.