APPENDIX ELEVEN



194            C2             PROMPT
     Prompt character.

200            C8             COLOR
     Stores the COLOR number used in a PLOT or DRAWTO statement.
     The statement COLOR x can be replaced by POKE 200,x. Same
     as location 763 ($2FB), but BASIC takes the value from 200 and
     loads it into 763 before drawing or filling. From Judson Pewther,
     New York.

202            CA             LOADFLG
     Load in progress flag.

210,211        D2,D3          ....
     BASIC floating-point work area. $D2 is used for the variable
     type, $D3 for the variable number and length of the FP
     mantissa.

212,213        D4,D5          FR0
     Used by the USR command to return a two-byte number to
     BASIC. If you store nothing here, then the equation
     "I=USR(address, variables)" returns the address of the USR sub-
     routine. Otherwise, you can store an integer (range 0-65535)
     here which becomes the value of the USR function, From Judson
     Pewther. New York.

522,523        20A,20B        VSERIN
     Serial input ready vector.

524,525        20C,20D        VSEROR
     Serial output ready vector.

528-533        210-215        POKEY timers
     In "From Here to Atari" in Micro, June and December 1983,
     Paul Swanson explained how POKEY timers work--properly.
     The manuals have an inaccurate description that causes your
     system to lock up. The method below is taken from those issues.

     This is described for channel 1; it can be used in channels 2
     and 4 (not 3) by selecting the appropriate control and interrupt
     vectors. First, POKE AUDCTL (53768; $D208) with a frequency
     value (0 = 64 kilohertz, 1 = 15 kilohertz, 96 = 1.79 megahertz).
     (You can actually change frequency between interrupts if you
     wish.) Next, set the channel control register (53761; $D201). Enter
     your interrupt routine and POKE its address into 528, 529 ($210,
     $211).