Commodore 1581 - Freeing Blocks

120 PRINT#5,"I THINK
THEREFORE I AM" Write a message to buffer.
130 T = 1 :S = 1 Start at first track & sector.
140 PRINT#15,"B-A";0;T;S Try allocating it.
150 INPUT#15,EN,EM$,ET,ES See if it worked.
160 IF EN=0 THEN 210 If so, we're almost done.
170 IF ENO65 THEN PRINT "NO BLOCK"
EN,EM$,ET,ES:STOP means already allocated.
180 IF ET=0 THEN PRINT
"DISK FULL":STOP If next track is 0, we're out of room.
190 IF ET=40 THEN ET=4l:ES = 0 Don't allocate the directory.
200 T=ET:S = ES:GOTO 140 Try suggested track & sector next.
210 PRINT#15,"U2";5;0;T;S Write buffer to allocated sector.
220 PRINT "STORED AT:",T,S Say where message went
230 CLOSE 5:CLOSE 15 and tidy up.
240 END
FREEING BLOCKS
The BLOCK-FREE command is the opposite of BLOCK-ALLOCATE.
It frees a block that you don't need any more, for re-use by the DOS.
BLOCK-FREE updates the BAM to show a particular sector is not in use,
rather than actually erasing any data.
FORMAT FOR BLOCK-FREE COMMAND:
PRINT#15,uBLOCK-FREE";drive #;track #;sector #
abbreviated as: PRINT#15,"B-F";drive #;track #;sector #
where "drive #" is the drive number, 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 FORMAT:
PRINT#15,"B-F:'';drive #;track #;sector #
EXAMPLE:
To free the sector in which we wrote our name in the BLOCK
WRITE example, and allocated in the first BLOCK-ALLOCATE example,
we could use the following command:
PRINT#15/'B-F";0;l;l
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