738-739



     will normally be passed back to the DOS menu. However, DOS
     can be forced to pass control to any specific address by storing
     that address here. If RUNAD is set to 40960 ($A000), then the left
     cartridge (BASIC if inserted) will be called when the program is
     booted.

     With DOS 1.0, if you POKE the address of your binary load file
     here, the file will be automatically run upon using the DOS
     Binary Load (selection L). Using DOS 1.0's append (/A) option
     when saving a binary file to disk, you can cause the load address
     POKEd here to be saved with the data. In DOS 2.0, you may
     specify the initialization and the run address with the program
     name when you save it to disk (i.e.,
     GAME.OBJ,2000,4FFF,4F00,4000). DOS 2.0 uses the /A option
     to merge files. In order to prevent your binary files from running
     automatically upon loading in DOS 2.0, use the /N appendage to
     the file name when loading the file.

     For users of CompuServe, there is an excellent little BASIC
     program (with machine language subroutines) to create autoboot
     files, chain machine language files with BASIC and to add an 850
     autoboot file in the Popular Electronics Magazine (PEM) access
     area. It is available free for downloading.

738-739        2E2-2E3        INITAD
     Initialization address read from the disk. An autoboot file must
     load an address value into either RUNAD above or INITAD. The
     code pointed to by INITAD will be run as soon as that location is
     loaded. The code pointed to by RUNAD will be executed only
     after the entire load process has been completed. To return
     control to DOS after the execution of your program, end your
     code with an RTS instruction.

740            2E4            RAMSIZ
     RAM size, high byte only; this is the number of pages that the top
     of RAM represents (one page equals 256 bytes). Since there can
     never be less than a whole page, it becomes practical to measure
     RAM in those page units. This is the same value as in RAMTOP,
     location 106 ($6A), passed here from TRAMSZ, location 6. Space
     saved by moving RAMSIZ or RAMTOP has the advantage of
     being above the display area. Initialized to 160 for a 48K Atari.

741,742        2E5,2E6        MEMTOP
     Pointer to the top of free memory used by both BASIC (which
     calls it HIMEM) and the OS, passed here from TRAMSZ, location
     6 after powerup. This address is the highest free location in RAM
     for programs and data. The value is updated on powerup, when
     RESET is pressed, when you change GRAPHICS mode, or when
     a channel (IOCB) is OPENed to the display. The display list starts