INTRODUCTION



     Well, our first task will be to decide what seven languages we will
use. First step in the solution: find out what languages are available on
the Atari computers. Here's my list:

     Atari BASIC
     BASIC A +
     Atari Microsoft BASIC
     Forth
     C
     Pascal
     PILOT
     LISP
     Assembler/Machine Language

     Does it match yours? You don't get credit for more than one
assembler or more than one Forth. And, actually, you shouldn't get
credit for Microsoft BASIC, since it uses exactly the same method as
Atari BASIC. And I will tell you right now that I will not attempt this
task in LISP. If you are a LISP fanatic, more power to you; but I don't
have any idea of how to approach the problem with Datasoft's LISP (the
only LISP currently available on the Atari).
     Anyway, let's tackle these languages one at a time.

Atari BASIC And Microsoft BASIC
Well, how about two at a time this one time? The implementation really
is the same for these two languages.
     Actually, the first part of this problem set is done for you in Atari
BASIC: the POSITION statement indeed does exactly what we want
(POSITION H,V will do the assigned task). But that's cheating, since
the object of these problems is to discover how to do machine level
access without such aids.
     Step 1 is to look at the memory map and discover that COLCRS, at
locations 85 and 86, is supposed to be the current graphics cursor
column (COLumn of CuRSor). Also, ROWCRS (ROW of CuRSor) at
location 84 is the current graphics cursor row.
     Let's tackle the row first. Assuming that the row number is in the
variable "V" (as specified above), then we may set the row cursor via
"POKE 84,V". And, in a like manner, we may say "V = PEEK(84)" to
assign the current position to "V". Now that's fairly straightforward: to
change a single memory location, use "POKE address,value"; to
retrieve the contents of a single memory location, use
"PEEK(address)". Virtually anyone who has programmed in BASIC on
an Atari is at least familiar with the existence of PEEK and POKE, since
that is the only method of accessing certain functions of the machine
(and since the game programs published in magazines are loaded with
PEEKs and POKEs).
     But now let's look at the cursor column, specified as being