Code:
 Your code
loop:
FOR letters = STRING[0] to STRING[9]

serout PortB.6,T9600,[254,128,"string is ",(LETTERS)]
pause 500
NEXT letters
goto loop
I think it should be done like this
Code:
for letters = 0 to 9
  serout PortB.6,T9600,[254,128,"string is ",(string[LETTERS])]
next