Block-Read - Commodore 1551 User Manual

channel is opened much like other files, except that the pound sign (#), optionally
followed by a memory buffer number, is used as a file name.
FORMAT FOR DIRECT ACCESS FILE OPEN STATEMENTS:
OPEN file # ,device #. channel #, "#buffer #"
where "file #" is the file number, "device #" is the disk's device number, normally 8;
"channel #" is the channel number, a number between 2 and 14 that is not used by other
files open at the same time; and "buffer #", if present, is a 0, I, 2, or 3, specifying the
memory buffer within the 1551 to use for this file's data.
EXAMPLES:
If we don't specify which disk buffer to use, the 1551 will select one:
OPEN 5,8,5,"#"
Or we can make the ehoice ourselves:
OPEN 4,8,4," #2"
BLOCK-READ
The purpose of a Block Read is to load the contents of a specified sector into a file
buffer. Although the Block Read command (B-R) is still part of the DOS command set, it
is nearly always replaced by thc U I command (See chapter 9).
FORMAT FOR THE BLOCK-READ COMMAND:
PRINT#15, "Ul"; channel #; drive #: track #; sector #
whcre "channel #" is the channel number specified when the file into which the block
will be read was opened, "drive #" is the drive number. always
°
on the ISS I. and
"track #" and "sector #" are respectively the track and sector numbers containing the
desired block of data to be read into the file buffer.
ALTERNATE FORMATS:
PRlNT#15,"Ul:"channel #;drive #;track #;sector #
PRINT#15,"UA:"ehannel #;drive #;track #;sector #
PRINT#15,"Ul:channel #,drive #,track # ,sector #"
56