Замена байта (HEX) в файле

DECLARE SUB help ()
DEFINT A-Z
' This program patches old Pascal EXEs 
' performing replace DIV CX -> NOP NOP
DIM p AS LONG, a AS STRING * 8192
PRINT "Pascal bad code fix"
s$ = CHR$(&HF7) + CHR$(&HD0) + CHR$(&HF7) + CHR$(&HD2) + CHR$(&HB9) + CHR$(&H37) + CHR$(&H0) + CHR$(&HF7) + CHR$(&HF1)
fi$ = LTRIM$(RTRIM$(COMMAND$))
IF fi$ = "" THEN help: END
ON ERROR GOTO etrap
er = 0
OPEN "i", 1, fi$: CLOSE 1
ON ERROR GOTO 0
IF er THEN help: END
SHELL "attrib -r " + fi$ + ">nul"
OPEN "b", 1, fi$
p = 0
WHILE NOT EOF(1)
GET 1, , a
v = INSTR(a, s$)
IF v THEN GOTO patch
p = p + 8192
WEND
PRINT "Pascal bad code not found"
CLOSE
END
 
patch:
SHELL "copy/b " + fi$ + " *.ex$>nul"
p = p + v + 6
x = &H9090
PUT 1, 1 + p, x
CLOSE
PRINT "Patching Ok"
END
 
etrap:
er = ERR
RESUME NEXT
 
SUB help
PRINT "Fixing ERROR 200 (zero devision) in old Pascal EXEs"
PRINT "Usage:"
PRINT "PAT200 filename.exe"
END SUB

OPEN "test.dat" FOR BINARY AS #1
SEEK #1, 5
test = 5
PUT #1, , test

DIM varname AS STRING*1

DIM test AS STRING * 1
OPEN "test.dat" FOR BINARY AS #1
SEEK #1, 5
PUT #1, , test

'qbasic
DEFINT A-Z
DIM a AS STRING * 1
CLS
fil$ = "bintest.txt"
OPEN fil$ FOR OUTPUT AS #1
PRINT #1, "123456789"
CLOSE #1
GOSUB show
OPEN fil$ FOR BINARY AS #1
a = CHR$(42)
PUT #1, 5, a
CLOSE #1
GOSUB show
SLEEP
END
 
show:
OPEN fil$ FOR INPUT AS #1
LINE INPUT #1, b$
PRINT b$
CLOSE #1
RETURN