FREE Blocks

This routine allows you to find the number of free blocks with out displaying the catalog.

It will return the number of free blocks in the BC register, so it can be accessed from basic with PRINT USR FREEBL or LET x=USR FREEBL .

00010 FREEBL DI
00020        CALL 98          - turn on the Lkdos cartridge
00030        LD A,0
00040        LD (curtrk),A    - move the disk drive to
00050        CALL TRACK       - block 0  (side 0 track 0)
00060        CALL LOADBF      - load disk to buffer
00070        LD C,0           - set counter to 0
00080        LD HL,data       - set HL to start of track-map
00090 USED   INC HL           - first block always used anyway
00100        LD A,(HL)
00110        CP 255           - 255 marker means 'end of track-map
00120        JR Z,EXIT        - if so then exit
00130        CP 245           - 245 marker means 'block used'
00140        JR Z,USED        - if used then move on to next one
00150        INC C            - must be a free block,update count
00160        JR USED          - continue searching for free blocks
00170 EXIT   LD B,0
00180        LD A,(98)        - turn cartridge off
00190        EI
00200 RET