1801



     (76): JMP command to next address in bytes seven and eight.

     7,8     707,708   Boot read continuation address
     (LSB/MSB).

     9       709       SABYTE: Maximum number of concurrently
     OPEN files. The default is three (see 1801 below).

     10      70A       DRVBYT: Drive bits: the maximum number
     of drives attached to the system. The default is two (see 1802
     below).

     11      70B       (unused) Buffer allocation direction, set to
     zero.

     12,13   70C,70D   SASA: Buffer allocation start address. Points
     to 1995 ($7CB) when DOS is loaded.

     14      70E       DSFLG: DOS flag. Boot flag set to non-zero
     Must be non-zero for the second phase of boot process. Indicates
     that the file DOS.SYS has been written to the disk; zero equals no
     DOS file, one equals 128 byte sector disk, two equals 256 byte
     sector disk.

     15,16   70F,710   DFLINK: Pointer to the first sector of DOS.SYS
     file.

     17      711       BLDISP: Displacement to the sector link byte
     125 ($7D). The sector link byte is the pointer to the next disk
     sector to be read. If it is zero, the end of the file has been
     reached.

     18,19   712,713   DFLADR: Address of the start of DOS.SYS
     file.

     20+     714+      Continuation of the boot load file. See the
     OS User's Manual and Chapter 20 of Inside Atari DOS.

     Data from the boot sector is placed in locations 1792 to 1916 ($700
     to $77C). Data from the rest of DOS.SYS is located starting from
     1917 ($77D). All binary file loads start with 255 ($FF). The next
     four bytes are the start and end addresses (LSB/MSB),
     respectively.

1801           709            SABYTE
     This records the limit on the number of files that can be open
     simultaneously. Usually set to three, the maximum is seven (one
     for each available IOCB -- remember IOCB0 is used for the
     screen display). Each available file takes 128 bytes for a buffer,
     if you increase the number of buffers, you decrease your RAM
     space accordingly. You can POKE 1801 with your new number to
     increase or decrease the number of files and then rewrite DOS
     (by calling DOS from BASIC and choosing menu selection "H")
     and have this number as your default on the new DOS.