Table of Contents
Advertisement
As changes occur to the BAM in DOS memory, the BAM on disk will be
updated to reflect these changes. Updated to the BAM occur when a program is
SAVEd or a CLOSE or DCLOSE is performed on a new RELative or SEQuen-
tial data file.
THE DISK OPERATING SYSTEM (DOS)
The DOS is responsible for managing information exchange between disk con-
troller and the computer.
The DOS performs many functions which are transparent to the user but which
are vital to the operation of the system. For example, the DOS monitors the
input/output (I/O) of the disk so that channels are properly assigned and that
no lengthy waits for an open channel occur. In addition to monitoring of disk
I/O, the DOS also uses the channel structure to search the directory and to
delete and copy files.
There is another function of DOS called DOS Support which was used during
hardware checkout in Chapter 2. Review the Performance Test procedure and
observe the special symbols of DOS Support which were used to duplicate and
initialize the disks before these procedures were fully explained to the user.
Because of its ease of use, DOS Support symbols were easier to implement at
that point than attempting to explain the programming procedures they replace.
It is now appropriate to briefly discuss how DOS Support can enhance and
simplify you knowledge of operating your Commodore computer.
The first file on the TEST DEMO diskette that comes with your disk drive is the
DOS SUPPORT PROGRAM. This program, when loaded into computer
memory, permits the user to enter abbreviations from many disk commands.
For example, disk commands which would normally be transmitted to the disk
using the PRINT#1fn,"commandstring" format may be transmitted via DOS
SUPPORT by preceding the command with > or @. Typing slash (/) followed
by a program name and RETURN will cause DOS SUPPORT to load that
program into memory. Replacing certain disk commands with DOS Support
special symbols can simplify learning about your Commodore computer by
providing a faster method to communicate with the disk.
Chapter 7 contains detailed instructions concerning the use of these special
symbols and their limitations.
17
Advertisement
Table of Contents
