I just realised how wonderfull that randomize command is

. You can encrypt and decrypt any file with this. If you don't provide the correct numeric code you will simply get a mess when decrypting...
repeat : cls : input "[e. Encrypt] | [d. Decrypt] : ",k$ : until k$="e" or k$="d"
repeat : input "File name: ",name$
if file exist(name$)=0 then print " File does not exist!"
until file exist(name$)=1
repeat : input "Code: ",code$ : code=val(code$)
if code<1 then print " Code has to be a number greater 0!"
until code>0
randomize code : open to read 1,name$ : open to write 2,"temp.dat" : size=file size(name$)
for s=1 to size
read byte 1,b
if k$="e"
b=b+rnd(255)
if b>255 then dec b,256
else
b=b-rnd(255)
if b<0 then inc b,256
endif
write byte 2,b
next s
close file 1 : close file 2 : delete file name$ : rename file "temp.dat",name$
Smile and be happy, things could be worse!
So I smiled and was happy, and things got worse...