0  ' CODER.BA Encryption program. Revised 7/16/87
1 ' Features: All in Basic without
2 ' calls. Therefore easily translated
3 ' to other machines. Suitable for 
4 ' Electronic Mail. Uses only ASCII 
5 ' 33 to 126, AND ignores CR's & LF'S 
6 ' & Spaces, including extras added in
7 ' transmission. Marks File start 
8 ' with "XX  X" for correct
10 ' Start point of Decoding. 
11 'User has the option, whether to
12 'print Spaces & Extras. Also,
13 'now runs faster.
15 CLEAR0:CLEAR1000:MAXFILES=2:DEFINTF,N,R,Y,Z:DEFSTRX
20 CLS:INPUT"Source File";F1$:INPUT"Target File";F2$
30 PRINT"1] Code":INPUT"2] Decode";F:IFF<>1ANDF<>2GOTO30
34 IFF=2THENR=1:GOTO40
35 INPUT"1] Spaces 2] No Spaces";R:IFR<>1ANDR<>2GOTO35
40 INPUT"Enter a 4 digit Number";NU:NU$=STR$(NU):NU$=RIGHT$(NU$,LEN(NU$)-1)
50 N1$=LEFT$(NU$,1)+RIGHT$(NU$,1)
55 IFVAL(N1$)>20THENN1=VAL(LEFT$(N1$,1))+VAL(RIGHT$(N1$,1))ELSEN1=VAL(N1$)
60 N2$=MID$(NU$,2,2)
65 IFVAL(N2$)>20THENN2=VAL(LEFT$(N2$,1))+VAL(RIGHT$(N2$,1))ELSEN2=VAL(N2$)
70 OPENF1$FORINPUTAS1:OPENF2$FOROUTPUTAS2
72 IFF=1THENPRINT#2,"XX  X";
74 IFF=2THENGOSUB200
80 IFEOF(1)GOTO150
90 X=INPUT$(1,1):IFASC(X)>32GOTO100
95 IFR=1GOTO130ELSEGOTO80
100 Y=Y+1:Z=ASC(X)
110 IFF=1THENZ=Z+YMODN1+N2ELSEZ=Z-YMODN1-N2
115 IFZ<33THENZ=Z+94
116 IFZ>126THENZ=Z-94
120 X=CHR$(Z)
130 PRINT#2,X;
140 GOTO80
150 CLOSE:MENU
200 IFEOF(1)GOTO250
205 A$=INPUT$(1,1)
210 IFA$<>"X"GOTO200
220 B$=B$+A$:IFLEN(B$)<5THENA$=INPUT$(1,1):GOTO220
240 IFB$="XX  X"THENRETURN
250 CLS:PRINT@130,"INVALID FILE":FORN=1TO1000:NEXT:CLOSE:MENU