Commodore 1541 - Page 41

The BLOCK-WRITE command writes the contents of the buffer to the block on
the disk along with the value of the buffer-pointer. The USER2 command writes the
buffer without disturbing the buffer-pointer value already stored on that block of the
diskette. This is useful when a block is to be read in with BLOCK-READ, updated
ihrough the BUFFER-POINTER and PRINTS statements, and then written back to
the diskette with USER2.
FORMAT FOR USER2 COMMAND:
PRlNT#file#, "U2:" channel; drive; track; block
Or
PRINT#filefl, -UB:" channel; drive; track; block
For a more complex sample program, see Appendix C.
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