String manipulation

[Nicholas Graham]

I'm writing a program that requires some string manipulations.  Let's say 
I have a string

s='x'

Now, the ascii code for 'x' is 0x78.  I want to be able to perform 
operations on this number, and print the character corresponding to the 
results of the operation.  For example, the pseudo-code looks like:

-read in string s from external file (for simplicity, we'll keep s='x')

-determine the code for s (should be 0x78 or 120 in base 10), store it in 
variable c

-add a literal to c (let's say c=c+1)

-find out which character corresponds to the new code c=0x79

-store the character in a new string s2

At the end of this, I want s2='y'

Any suggestions?

NG