Second attempt here. First I thought you were meaning to do something with the numbers from 5 to 11. Duhhh!
I guess this is something like a generator of every anagram possible from 5 to 11 characters in length. What is it you want to do with the results you get? Store them? Print them to screen?
One simple way to approach it would be to set up a system of nested FOR/NEXT loops, one inside the other, so that each letter was stepped by one. The ASCII values of A, B, C, D etc start at 65.
for ( int a = 65; a <= 90 ; a++ )
for ( int b = 65; a <= 90; b++ )
for ( c = 65; c <= 90; c++ )
You would need to add code to the fifth and subsequent loops to take into account the fact that in each of those there can be an invalid character, (91 - "[" seems a good choice), in which case you terminate that combination. This will offer you the 5, 6, 7, 8, 9, and 10 letter combinations and not just the 11 letter ones.
Knowing what you are going to do with the results is crucial however. Remember there are going to be a shed load