›<><><><><><><><><>><><>><><><><><><><>››      MORE BITS OF BASIC›      By M. Olin (WAUGI,MACE)›Reprinted   from  the  Michigan  Atari›Magazine›››'PROTECTING' YOUR SOFTWARE››You  say you've written a program, and›you  spent  a  lot  of hours making it›"just  right?"   You've  written  some›pretty nice routines that you're quite›proud  of,  but  you  don't  want just›anybody  to have access to it?  Here's›a  couple of hints that might help you›keep  some  prying  eyes  from viewing›your work.››DISABLE THE BREAK KEY››The  very  first  line of your program›should look like this:››     10 POKE 16,64:POKE 53774,64››Effectively, we have told the computer›to  ignore  the  fact that the user is›pressing  the  BREAK  key.  Therefore,›the  user  cannot  "break  out" of the›program  and  look at your code.  But,›that's   only   the   beginning.   Any›Atarian  who  has had his/her computer›for more than 2 weeks should know that›all  you'd  have to do is press RESET,›and we'd be back to Square 1.››COLD STARTING››Add  the following command to line 10,›making  sure  to  separate it from the›previous commands with a colon(:).››     POKE 580,1 ››Now,  whenever  the  user  presses the›RESET key alone, the computer will act›almost  as if you had turned the power›off  and  back  on  again.   In  other›words,   it  will  "reboot",  and  the›program   that  was  running  will  be›erased from memory.››So  far  so  good!   Now  you  need  a›routine   that  permits  the  approved›users  to have access to your program,›but those persons you want to keep out›will have to be "filtered" somehow.  A›"password" seems in order here.››     19 DIM PASS$(20)›     20  INPUT  PASS$:IF  PASS$<>"Your›Password" THEN NEW:END››All  persons who are using the program›must  know  the password, which can be›up to 20 characters long.  Notice that›it  is  upper/lower  "case sensitive."›If they enter it wrong, the program is›erased   from  memory.   Zip.   Kaput.›Gone.   And,  just  to  make sure that›"the   enemy"   can't   discover  your›password    by   staring   over   your›shoulder,  we're  going  to  make sure›that  the  characters  you  type never›appear on the screen.››     15 X=PEEK(559):POKE 559,0››This  command  will turn off the chip,›called   ANTIC,   that   drives   your›monitor.   The  screen will turn black›with  no visible text, and will remain›in  this  state until you turn it back›on again, which you will not do unless›the proper password is entered in line›20.  if the correct password is given,›then this line will complete the job:››     25 PRINT "<ESC><SHFT-CLEAR>":POKE›559,X›     30 REM Your program starts here.››Let's check our progress:  The program›won't  run  if  they  don't  know  the›password.   They can't RESET, and they›can't press BREAK and LIST the program›to  look  at  your  password.   What's›left?››We  have  to find a way to prevent the›uninvited   user   from   LOADing  the›program  and  LISTing  the  lines that›contain  your  password, since none of›the  above  commands  will take effect›until   after   the   program   starts›running.   This  part  gets  a  little›tricky, so you will want to type it in›EXACTLY  as it is written here.  After›your    program   is   completed   and›"debugged"  to  your satisfaction, you›need  to  add  these lines.  Note that›your  program  must  not  ever GOTO or›GOSUB to these lines.››     32761›BOTTOM=PEEK(131)*256+PEEK(130›     ):TOP=PEEK(133)*256+PEEK(132)›     32762  FOR  X=BOTTOM  TO TOP:POKE›X,15›     5:NEXT X›     32763›FINISH=PEEK(139)*256+PEEK(138›     ):POKE            FINISH+2,0:SAVE›"D:filename.›     ext":NEW››A WORD OF CAUTION:  Make sure you SAVE›a  copy  of  your  program  before you›continue     with     the    following›instructions.   Store  this  copy in a›safe place as it is the only copy that›can  EVER  be  LISTed again.  Not even›the  approved  password  user can LIST›your  program once these routines have›been  performed,  so take good care of›this "source" disk!››Ready?   Make  sure  the disk on which›you  want  the  "protected" version of›your  program  is  in  Drive  1,  then›type:››     GOTO 32761››and   press   <RETURN>.   Here's  what›happens:   The  FOR/NEXT  loop in line›32762  will  cause  all  the  variable›names   which   are   used   in   your›program(and  stored  in  the  Variable›Name   Table)   to  be  replaced  with›CHR$(155),  the  ATASCII  value in the›POKE  statement  in line 32762).  When›this   happens,  the  program  can  no›longer   be  LISTed,  nor  can  it  be›LOADed!  In fact, the only way to LOAD›and  RUN this program ever again is by›issuing   the   RUN   "D:filename.ext"›command from BASIC.››And,  there you have it!  A reasonably›good,  but not absolutely perfect, way›to "protect" your software.››()  )(  )( )( )( )( )( )( )( )( )( )(››