*><*<>*¢ This article reprinted from the¢ M.A.G.I.C. Newsetter Nov. 1990, by OL'¢ HACKERS, with thanks. It adds to the¢ prior reported PEEKS and POKES, along¢ with machine language programming¢ tips.¢¢ Atari BASIC Programming Helps¢ By Hawke, Sysop of the Nine Hells¢ Information Exchange of Philadelphia,¢ (215) 785-2625¢¢ As a whole, standard Atari BASIC¢ is not the best programming medium in¢ existence. One of the major problems¢ stems from the fact that it was¢ created too many years ago. Be that¢ as it may, new programmers are being¢ subjected to it now, unnecessarily,¢ and must deal with a user unfriendly¢ language. (Editor. I strongly¢ disagree. I find BASIC a fun¢ programing tool, in spite of its¢ limitations. A.P.)¢¢ Inspired by a set of PASCAL¢ notes, I venture to write these helps,¢ so that BASIC programmers can learn¢ from my experience, as well as the¢ Phoenix, with whom I have consulted¢ about this text. Any questions or¢ comments are welcomed. Contact myself¢ or Phoenix through the above Bulletin¢ Board number.¢¢ The following sections deal with¢ POKE's, PEEK's, small machine language¢ routines, some program listings, BASIC¢ tricks, and other such nonsense.¢¢ ROUTINE ONE:¢ (Three Lower case H's), (INVERSE¢ asterisk), (Capital L), (Capital V),¢ (INVERSE Lower case D)¢¢ ROUTINE TWO:¢ (Lower case H), (INVERSE Quote),¢ (Control P), (SPACE), (Upper case V),¢ (INVERSE lower case D), (INVERSE¢ control A), (INVERSE capital T),¢ (INVERSE close parenthesis), (Control¢ ,), (INVERSE control E), (INVERSE¢ capital U), (Control .)¢¢ (Ed. note: When typing in the above¢ routines, DON'T type in the commas.)¢¢ Section One:¢¢ Machine Language Routines¢¢ Many BASIC programmers are fearful of¢ using machine language subroutines in¢ their programs. I know this to be¢ true, because I was one of them. I¢ have since gotten over that fear,¢ after collaboratively writing the P-¢ Net 4.5 BBS system with the Phoenix,¢ and have converted a few others.¢¢ If you have ever used Character¢ Fonts, made with any number of font¢ editor programs (Envision, SuperFont,¢ etc.), you know that they can be used¢ to create fancy text, graphics, or¢ maps. The problem with them is that¢ one must enter in 1,024 bytes, poke¢ them into a page of memory, and then¢ change the register holding the¢ address of the ROM set to the new set. ¢ To do all this takes a bit of time to¢ do. The following machine language¢ subroutine loads in a character set¢ and adjusts the register in seconds.¢¢ 1 POKE 881,0:OPEN #3,4,128,"D:SET.DAT"¢ :POKE 884,0:POKE 885,112:POKE 888,0¢ :POKE 889,4:POKE 882,7¢ ¢ 2 AA=USR(ADR("ROUTINE ONE"),48):CLOSE¢ #3:POKE 54277,4:POKE 756,112¢¢ * SET.DAT would be the font.¢¢ * Poking 885,112 tells the machine¢ which page of memory the redefined¢ character set will be stored in (since¢ a character set MUST start at the¢ beginning of a page).¢¢ * To return to the ROM set, simply¢ POKE 756,224. To go back to the¢ redefined font, POKE 756,112.¢¢ **¢ The next machine routine deals¢ with speedy Disk I/O. Atari BASIC¢ programmers know that using the INPUT¢ and GET commands with disk files is¢ SLOW, especially when using large¢ amounts of data. The following¢ machine language subroutine solves¢ this problem by allowing you to read¢ an entire file into a string,¢ virtually, in seconds. This can be¢ useful when printing out text files or¢ editting machine language programs (by¢ string search, etc.).¢¢ 900 CLOSE #1:OPEN #1,4,0,"D1:filename¢ .ext"¢¢ 1000 CE=INT(MEM/256):POKE 857,CE:POKE¢ 856,MEM-256*CE:BUF$(MEM)=" ":BOF=C1¢¢ 1010 POKE 853,INT(ADR(BUF$)/256):POKE¢ 852,ADR(BUF$)-PEEK(853)*256¢¢ 1020 DUM$="ROUTINE TWO":POKE 850,7:IF¢ USR(ADR(DUM$))=136 THEN BOF=C0¢¢ 1030 X=PEEK(856)+256*PEEK(857):BUF$¢ =BUF$(1,X):RETURN¢¢ * MEM is the amount of characters¢ that BUF$ is dimensioned to hold.¢¢ * In line 1000, the routine divides¢ up that number into two numbers with a¢ formula (16-bit conversion). This¢ tells the subroutine the maximum¢ length the string can hold. It then¢ sets the last character in BUF$ equal¢ to a character, thus, it defines BUF$¢ as being full.¢¢ * Line 1010 divides the address¢ (starting location) of BUF$ by the¢ same 16-bit conversion, and stores it¢ for the subroutine, so that it knows¢ where to start putting the incoming¢ data.¢¢ * Line 1020 executes the machine¢ routine, and reads in the data,¢ checking for an End Of File (EOF)¢ error; #136. If such an error is met,¢ the variable BOF is set to zero.¢¢ * Line 1030 retrieves the number of¢ bytes long the routine loaded, and¢ tells BUF$ that it is X number of¢ characters long.¢¢ * If BOF=0, the user may account for¢ the EOF and jump back to the routine¢ after clearing BUF$.¢ * By using this routine, one can copy¢ files through BASIC. Simply, after¢ reading in a file, print the string to¢ disk.¢¢ 10 CLOSE #1:OPEN #1,8,0,"D1:destinat.¢ ion":PRINT #1;BUF$:CLOSE #1¢¢ **¢ The last machine language routine¢ is a clock. The Atari has a built in¢ clock and doesn't even use it. It¢ follows the electrical current in the¢ U.S., which flows at 60Mhz. The¢ following routine, written by the¢ Phoenix, sets up a clock, using page 6¢ memory (1536) to store the data, and¢ operates during each VBI (Vertical¢ Blank Interrupt). You merely have to¢ supply the current hour, minutes,¢ seconds, and 60ths of a second. You¢ can retrieve the current time by¢ merely using PEEK commands. The only¢ stricture is that if you use a¢ graphics command (eg. GRAPHICS 0) you¢ must re-initialize the clock.¢¢ 32700 FOR A=1 TO 105:READ B:POKE¢ 1535+A,B:NEXT A¢¢ 32705 ? "Enter Military Time as Hours,¢ Minutes,Seconds,60ths":INPUT H,M,S,SS¢¢ 32710 X=USR(1611,H,M,S,SS)¢¢ 32720 DATA¢ 238,115,6,173,115,6,201,60,240,3,76,¢ 95,228,169¢¢ 32730 DATA¢ 0,141,115,6,238,114,6,173,114,6,201,¢ 60,240,3,76,95,228,169,0,141¢ ¢ 32740 DATA¢ 114,6,238,113,6,173,113,6,201,60,240,¢ 3,76,95,228,169,0,141,113,6¢ 32750 DATA¢ 238,112,6,173,112,6,201,24,240,3,76,¢ 95,228,169,0,141,112,6,76,95¢ ¢ 32751 DATA¢ 228,104,104,104,141,112,6,104,104,141,¢ 113,6,104,104,141,114,6,104,104,141¢¢ 32752 DATA¢ 115,6,169,6,170,160,0,76,92,228,0¢¢ * The PEEK locations for the time¢ are:¢ Hours - 1648¢ Minutes - 1649¢ Seconds - 1650¢ 60ths - 1651¢¢ * The program first pokes the¢ machine language subroutine into page¢ 6 memory, and then prompts you to¢ enter the time.¢ * It then GOSUBS the machine¢ subroutine, sending with it the values¢ of the current time, and then starts¢ the clock.¢ * After a GRAPHICS command, just¢ PEEK in the values of the correct time¢ into H, M, S, and SS, and reintialize¢ the clock.¢¢ *****¢ Section Two: BASIC Tricks¢¢ Since Atari BASIC hasn't many special¢ features, one must compensate by¢ "tricking" the system. These "tricks"¢ are actually ways around BASIC that¢ speed up processing, format output,¢ etc.¢¢ The first trick deals with filling a¢ string with one character. To fill a¢ string with 1,000 spaces, one would¢ usually do this:¢¢ 10 DIM L$(1000)¢ 20 FOR A=1 TO 1000¢ 30 L$(A,A)=" "¢ 40 NEXT A¢¢ This method, though fine programming,¢ is SLOW. The trick around it is a¢ quirk in the BASIC; well, not actually¢ a "quirk", but a hidden back door. ¢ The line below is the aforementioned¢ routines equivalent.¢¢ 10 DIM L$(1000):L$="":L$(1000)="":¢ L$(2)=L$¢¢ * Not only is this routine shorter,¢ but it's almost instantaneous,¢ depending on the size of the string. ¢ I find a one second wait for strings¢ in the xx,xxx digit range, but I think¢ that it's worth the wait.¢¢ * Side Note: If you DIMension a¢ string at 1000, and aren't filling the¢ ENTIRE string with one character, say¢ 500 from a 1,000 character string, and¢ use the formula [L$=" ":L$(500)="¢ ":L$(2)=L$], it will fill it with 501¢ spaces. To clear this up, all you¢ need do, is put "L$=L$(1,500))" after¢ setting it. This is true, even when¢ filling 998 of the 1,000 characters.¢¢ **¢ The next "trick" deals with the¢ INPUT statement. Anyone who has¢ programmed using the INPUT statement¢ knows that it puts a "?" on the screen¢ to signify an input request. This can¢ be bothersome to some, especially me,¢ when they want to make prompts look¢ nice. That "?" just looks outta¢ place, and sometimes is included in¢ the returned variable.¢¢ There are two solutions. One is to¢ write your own "Get-Line" routine,¢ using an open keyboard buffer, getting¢ keypresses, adjusting for backspaces¢ and control characters, and using up¢ memory, OR...¢¢ Use the following Input command that¢ is totally the equivalent of your¢ regular INPUT.¢¢ INPUT #16,variable¢¢ That's right! An input through¢ standard Atari BASIC without the¢ dreaded "?". It works exactly like¢ the standard INPUT command. Sure, you¢ could open a channel to the editor¢ (E:) yourself, but this method¢ requires no additional open buffers.¢¢ **¢ Ever want to intialize a disk from¢ BASIC? No, I don't mean just format¢ it, I mean put DOS on it too. Well, I¢ have good news and bad news. The GOOD¢ news is that you can, the bad news is¢ that that's ALL you can put on it;¢ DOS, no DUP. In fact, the writing of¢ DOS to the disk is as fast as writing¢ from DOS itself!¢¢ OPEN #1,8,0,"D1:DOS.SYS":CLOSE #1¢¢ Yes, that's it! All DOS's except¢ SpartaDOS and TOPDOS will work, even¢ the OSA+ DOS's. You have just written¢ DOS to your disk from BASIC.¢¢ **¢ Did you ever want to Re-Boot (Warm¢ Boot) the computer from BASIC without¢ hitting System Reset? Try this:¢¢ X=USR(58487)¢¢ This will "Warm Boot" the computer,¢ but unlike the RESET key, it is the¢ equivalent of turning the machine OFF¢ and ON again; so you might call it an¢ artificial COLD boot. You may hold¢ down OPTION as this boot takes place¢ to disengage BASIC. Its Hexadecimal¢ number is E477. You can do it from a¢ DOS as well.¢¢ ******¢ Section Three: PEEK's and POKE's¢¢ Did the speed of Atari BASIC¢ processing ever bug you? Well,¢ there's a way to increase data¢ processing 33%. It will increase¢ problem solving speed, data¢ processing, and graphic plotting.¢¢ POKE 559,0¢¢ This POKE will shut down ANTIC, thus¢ shutting off the screen, so that¢ processing speed is increased. To¢ turn it back on, use POKE 559,34.¢¢ **¢ To find out what version of Atari¢ BASIC you have in your computer, you¢ simply:¢¢ PRINT PEEK(43234)¢¢ A number 32 or less is revision A. ¢ The value 64 or less is revision B;¢ built into most XL's. And a number¢ greater than 64 is revision C; the¢ current version built into the XE¢ line. Though I have an old 800XL, for¢ some reason I have revision C built¢ in; a blessing!¢¢ **¢ Here are some keyboard POKE's to¢ play with:¢¢ * 755,004 - Turns character set¢ Upside -Down, and disables Inverse¢ video.¢¢ * 755,008 - Right-Side up character¢ set WITHOUT Inverse video.¢¢ * 755,013 - Upside-Down characters¢ WITH Inverse video.¢¢ * 755,010 - Right-Side up character¢ set with Inverse video (Normal mode).¢¢ ******¢ Special recognition to XLent software¢ and David Castell for creating the¢ fine word processor used to create¢ this text. BRAVO. (Editor: I concur.¢ Have been using it for years to make¢ up the newsletter! Am now trying to¢ learn about another FANTASTIC Word¢ Processor! A.P.)¢¢ Please send me comments concerning¢ these notes. A positive response¢ might warrant a Part Two.¢ Hawke ----------------¢ ¢ I downloaded this article from the¢ Pandora BBS (614) 471-9209 on¢ 10/22/89. It looks like it came from¢ the Nine Hells Information Exchange of¢ Philadelphia (PA) BBS, (215) 785-2625. ¢ I thought it might be good for those¢ still programming in Atari BASIC. I¢ hadn't seem most of the tips before¢ except the one on getting rid of the¢ question mark. I'll bet others¢ haven't either. I hope you find this¢ article helpful. ¢ GRANT, 8 BIT librarian for M.A.G.I.C.¢ <<>><<>>¢¢
