CRCFIX.324
CRC fixer for CDOS 3.24+

If a file will not load and the problem
is due to a CRC error, ("?CC Error-etc"
displayed) the machine language program
created by listing two (CRCFIX.CO) can
be used to bypass CRC errors in CDOS
rev 3.24 most of the time, as most CRC
errors are not due to actual physical
damage to the disk medium. The data
may have been altered; but better to
be able to retrieve a file with bad
data that you can attempt to restore
than not to be able to retrieve it
at all.

First, find out which track and sector
have the CRC error. Use the ML finder
program, FINDCC.CO, created by listing
one, or your own method. FINDCC.CO
reads all tracks sequentially and
announces CRC errors with a multiple
beep while displaying the track and
sector where they occur. Other errors
are announced with a single beep. It's
desirable to know which files contain
the CRC errors so you'll recognize the
sector contents when CRCFIX prints
them on the screen. You may want to use
DISKPP.CHP to find out where these
files are on the disk. Use the display
directory and display allocation table
options to trace which clusters the
file occupies, and then use the display
cluster option to verify the track and
sector where the CRC error occurs. Or
you can verify by exiting to Basic and
executing in immediate mode:
? DSKI$(0,T,S,0) -- where T=track #
and S = sector #. Of course, if only
one file has a CRC error, it's pretty
obvious.

Then run the CRCFIX.CO program created
by listing two. Answer the prompts with
the track and sector number. If there's
not a valid CRC error, then you'll get
a message and be re-prompted. The data
contained in that track and sector will
be displayed on the screen. If that
looks like the right sector, then press
the Y key and that sector will be
rewritten to the disk, eliminating the
CRC error in the process. Then you'll
be able to load the file and correct
any data that may have been altered.
It's easy to spot bad data in a DO
file. BA files are harder, but not
impossible. Of course, if the file was
a CO file, you're just trusting to
luck that it'll still run, as this
whole exercise is rather pointless when
you're unable to recognize and fix CO
program bytes.


Listing one:

0 ' Loader program to create FINDCC.CO
1 ' By Tim Ekdom  72575,1473
2 ' July, 1985
10 CLS:PRINT
20 IFHIMEM<>MAXRAMANDHIMEM<>57248THEN500
30 IFMAXRAM<57967THEN600
40 IFFRE(0)<1000THEN700
50 CLEAR256,57248
60 PRINT"Creating FINDCC.CO ..."
70 FORAD=57248TO57957
80 READ BY:POKEAD,BY
90 CK=CK+BY
100 NEXTAD
110 IFCK<>50614THENPRINT"Incorrect checksum...not loaded":END
120 CLS:PRINT:PRINT"Finished. Load/Run address is 57248"
130 SAVEM"FINDCC.CO",57248,57957,57248
140 END
500 PRINT"HIMEM <> MAXRAM. Is there a ML program"
510 PRINT "loaded (other than CDOS) that you want":PRINT"saved? (Y/N)"
520 A$=INKEY$:IFA$=""THEN520
530 IFA$="Y"ORA$="y"THENEND
540 IFA$="N"ORA$="n"THENCLS:PRINT:GOTO30
550 GOTO520
600 PRINT"Cannot load over MAXRAM":END
700 PRINT"Inadequate free RAM to save SDCOPY.":PRINT"Kill some files":END
1000 DATA205,49,66,205,34,66,33,207,224,205,88,90,205,34,66,33,224,224,205,88
1010 DATA90,205,34,66,205,34,66,33,239,224,205,88,90,205,203,18,254,13,202,214
1020 DATA223,254,27,202,72,224,254,3,194,193,223,195,72,224,62,18,33,100,225,119
1030 DATA62,255,35,119,43,43,119,205,34,66,33,83,225,205,88,90,33,100,225,52
1040 DATA62,19,190,194,24,224,62,1,119,35,52,62,80,190,202,39,224,58,58,246
1050 DATA254,37,244,34,66,62,32,231,58,101,225,111,38,0,205,212,57,62,32,231
1060 DATA205,190,224,218,73,224,205,179,224,218,88,224,195,236,223,205,34,66,33,10
1070 DATA225,205,88,90,205,34,66,33,20,225,205,88,90,205,203,18,230,31,254,25
1080 DATA202,184,223,254,14,194,57,224,201,205,34,66,33,37,225,205,88,90,205,34
1090 DATA66,195,51,224,205,41,66,33,101,225,58,99,225,190,202,104,224,205,34,66
1100 DATA62,67,187,202,125,224,33,46,225,205,88,90,38,0,107,205,212,57,195,137
1110 DATA224,205,41,66,205,41,66,33,54,225,205,88,90,33,66,225,205,88,90,58
1120 DATA101,225,111,38,0,205,212,57,33,74,225,205,88,90,58,100,225,111,38,0
1130 DATA205,212,57,205,34,66,58,101,225,50,99,225,195,236,223,33,100,225,94,35
1140 DATA86,35,255,66,2,201,205,66,114,167,200,254,27,202,205,224,254,3,194,190
1150 DATA224,55,201,32,67,68,79,83,32,67,82,67,32,70,105,110,100,101,114,0
1160 DATA32,40,69,83,67,32,61,32,65,98,111,114,116,41,0,32,73,110,115,101
1170 DATA114,116,32,100,105,115,107,44,32,112,114,101,115,115,32,69,110,116,101,114
1180 DATA32,0,32,70,105,110,105,115,104,101,100,0,32,65,110,111,116,104,101,114
1190 DATA63,32,40,89,47,78,41,32,0,32,65,98,111,114,116,101,100,0,32,69
1200 DATA114,114,111,114,32,0,32,67,82,67,32,101,114,114,111,114,58,0,32,84
1210 DATA114,97,99,107,32,0,32,83,101,99,116,111,114,32,0,32,82,101,97,100
1220 DATA105,110,103,32,116,114,97,99,107,58,0,255,0,0,0,0,0,0,0,0
1230 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1240 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1250 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1260 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1270 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1280 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1290 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1300 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1310 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1320 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1330 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1340 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1350 DATA0,0,0,0,0,0,0,0,0,0


Listing two:

0 ' Loader program to create CRCFIX.CO
1 ' By Tim Ekdom  72575,1473
2 ' July, 1985
10 CLS:PRINT
20 IFHIMEM<>MAXRAMANDHIMEM<>57296THEN500
30 IFMAXRAM<57967THEN600
40 IFFRE(0)<1000THEN700
50 CLEAR256,57296
60 PRINT"Creating CRCFIX.CO ..."
70 FORAD=57296TO57965
80 READ BY:POKEAD,BY
90 CK=CK+BY
100 NEXTAD
110 IFCK<>46886THENPRINT"Incorrect checksum...not loaded":END
120 CLS:PRINT:PRINT"Finished. Load/Run address is 57296."
130 SAVEM"CRCFIX.CO",57296,57965,57296
140 END
500 PRINT"HIMEM <> MAXRAM. Is there a ML program"
510 PRINT "loaded (other than CDOS) that you want":PRINT"saved? (Y/N)"
520 A$=INKEY$:IFA$=""THEN520
530 IFA$="Y"ORA$="y"THENEND
540 IFA$="N"ORA$="n"THENCLS:PRINT:GOTO30
550 GOTO520
600 PRINT"Cannot load over MAXRAM":END
700 PRINT"Inadequate free RAM to save SDCOPY.":PRINT"Kill some files":END
1000 DATA205,49,66,205,34,66,33,212,224,205,88,90,205,34,66,33,233,224,205,88
1010 DATA90,205,34,66,205,34,66,33,249,224,205,88,90,205,184,224,202,172,224,218
1020 DATA235,223,33,79,0,223,218,235,223,123,50,108,225,33,3,225,205,88,90,205
1030 DATA184,224,202,172,224,218,5,224,33,18,0,223,218,5,224,123,50,109,225,62
1040 DATA2,50,182,224,205,173,224,210,142,224,123,254,67,194,154,224,33,13,225,205
1050 DATA88,90,205,34,66,62,0,50,107,225,33,107,225,78,6,0,33,110,225,9
1060 DATA126,231,33,107,225,52,62,0,190,194,62,224,205,34,66,33,31,225,205,88
1070 DATA90,205,203,18,230,31,254,25,202,119,224,254,13,202,172,224,254,14,194,93
1080 DATA224,205,34,66,195,232,223,205,34,66,62,4,50,182,224,205,173,224,33,48
1090 DATA225,205,88,90,205,34,66,195,232,223,33,58,225,205,88,90,205,34,66,195
1100 DATA232,223,33,84,225,205,88,90,107,38,0,205,212,57,205,34,66,195,232,223
1110 DATA201,33,108,225,86,35,94,35,255,66,0,201,205,68,70,35,223,200,35,35
1120 DATA223,216,33,133,246,205,235,8,194,207,224,186,202,209,224,62,255,198,2,201
1130 DATA32,67,68,79,83,32,51,46,50,52,32,67,82,67,32,70,105,120,101,114
1140 DATA0,32,40,69,110,116,101,114,32,61,32,69,120,105,116,41,0,32,84,114
1150 DATA97,99,107,63,32,32,0,32,83,101,99,116,111,114,63,32,0,32,83,101
1160 DATA99,116,111,114,32,99,111,110,116,101,110,116,115,58,0,32,80,114,111,99
1170 DATA101,101,100,63,32,40,89,47,78,41,32,0,32,70,105,110,105,115,104,101
1180 DATA100,0,32,78,111,32,67,82,67,32,101,114,114,111,114,32,116,104,105,115
1190 DATA32,115,101,99,116,111,114,0,32,78,111,116,32,67,82,67,32,101,114,114
1200 DATA111,114,46,32,69,114,114,111,114,32,0,0,0,0,0,0,0,0,0,0
1210 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1220 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1230 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1240 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1250 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1260 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1270 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1280 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1290 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1300 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1310 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1320 DATA0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
1330 DATA0,0,0,0,0,0,0,0,0,0


Tim Ekdom
72575,1473
July, 1985