100 SYS65517:IFPEEK(781)=22THENMT$="":GOTO2999
110 MT$=""
2998 REM END: REM PROGRAM 3, UNSCRATCH FILES
2999 PRINTMT$
3000 INPUT "[147]WHICH SECTOR";S$: S=VAL(S$): IF S<0 OR S>19 THEN 3000
3010 PRINT "WHAT IS THE FIRST BYTE":PRINT"OF THE FILE YOU WISH"
3011 PRINT"TO UNSCRATCH?"
3020 INPUT BP$: BP=VAL(BP$): REM INPUT FILE TARGET BYTE FOR UNSCRATCH
3030 BS=(BP=2)+(BP=34)+(BP=66)+(BP=98)+(BP=130)+(BP=162)+(BP=194)+(BP=226)
3035 IFBS<>-1THEN3020:REM REJECT INVALID INPUT
3040 PRINT "SELECT FILE TYPE:"
3050 PRINT "  1. SEQUENTIAL"
3060 PRINT "  2. PROGRAM"
3070 PRINT "  3. USER"
3080 PRINT "  4. RELATIVE"
3090 PRINT "WHICH ONE?"
3100 GET A$: IF A$="" THEN 3100
3110 A=VAL(A$): IF A<1 OR A>4 THEN 3100: REM REJECT INVALID CHOICE
3120 B=A+128: REM SET INPUT BYTE TO MATCH DOS FILE CODES
3130 OPEN 15,8,15,"I": REM OPEN COMMAND CHANNEL TO DISK
3140 OPEN8,8,8,"#": REM OPEN DIRECT ACCESS CHANNEL TO DISK
3150 PRINT#15, "U1:"8;0;18;S: REM LOAD SECTOR CONTAINING FILE TO BE UNSCRATCHED
3160 PRINT#15, "B-P:"8;BP: REM SET BUFFER POINTER TO TARGET ADDRESS
3170 PRINT#8, CHR$(B);: REM CHANGE TARGET FILE CODE IN CHANNEL 8 BUFFER
3180 PRINT#15, "U2:"8;0;18;S: REM RETURN CHANGED CONTENTS TO TARGET SECTOR
3190 CLOSE 8: REM CLOSE DIRECT ACCESS CHANNEL
3200 CLOSE 15: REM CLOSE COMMAND CHANNEL
3210 REM GOTO 100: REM RESTART DISPLAY T&S PROGRAM WHEN FIRST REM REMOVED