If a disk contains a CRC error, it is sometimes helpful to determine the 
name of the file that contains the error so a backup copy of the file can be 
recopied over the bad file.  If the track and sector containing the error 
are known (can be found using FINDCC or SEARCH), the cluster containing the 
error can be calculated (see documentation for DISKPP).  Next, 
search the allocation table (using DISKPP) for the byte containing that 
cluster.  Now backtrack through the allocation table bytes (again see the 
documentation for DISKPP) until the cluster originating the file is 
found.  This will be the cluster that is not contained in any of the 
allocation table bytes.  Knowing this cluster, the directories and/or 
folders can be searched until the file which originates in that cluster is 
identified.

This enhancement to DISKPP.324 version 2.2 allows the user to find which 
byte of the allocation table contains a particular cluster value (between 1 
and 239).  Once the byte is known, the  table can be read byte by byte 
backtracking the file to its originating cluster.

When a cluster cannot be found, that cluster is the originating cluster for
the file (unless the allocation table is messed up).

The following lines should be merged into DISKPP.324.  Be sure you have 
merged DISKPP.BUG and any earlier updates first.

If you have previously merged DISKPP.UD2, you may just merge this
DISKPP.UD3 into that file.

430 CALL16954:GOTO9000
431 PRINT@280,E$;" Display a single byte? (Y/N)";
438 IN$="":PRINT" Byte number";:INPUTIN$:IFLEN(IN$)=0THEN150
440 R=PEEK(63033):IFR=8THENR=240ELSER=(R-1)*40
441 PRINT@R,;" Byte number  "+IN$+"   ";ASC(MID$(TA$,BN+1,1)):GOTO438
9000 PRINT@280,E$;" Find contents? (Y/N)";:GOSUB30:IFA$<>"Y"ANDA$<>"y"THEN431
9005 PRINT:PRINTP1$
9010 IO$="":PRINT@280," Contents to find";:INPUTIO$:IFLEN(IO$)
=0THENPRINT:GOTO431
9020 BO=VAL(IO$):IFBO<1ORBO>239THEN9010
9030 BN=INSTR(1,TA$,CHR$(BO))-1
9040 IFBN<0ORBN>239THENPRINT" Not found":GOTO9010
9050 IN$=STR$(BN):IN$=RIGHT$(IN$,LEN(IN$)-1)
9060 PRINT@240,;" Byte number  "+IN$+"   ";ASC(MID$(TA$,BN+1,1));:GOTO9010

WILLIAM SCHNEIDER
[70146,1107]