How do I increment a variable to the next or previous letter in the alphabet?

Question

I have a capital letter defined in a variable string, and I want to output the next and previous letters in the alphabet. For example, if the variable was equal to \'C\'

Answer 1

Well if you mean the 'ABC' then they split into two sequences a-z and A-Z, the simplest way I think would be to use a char variable and to increment the index by one.

char letter='c';
letter++;  // (letter=='d')

same goes for decrement:

char letter='c';
letter--; // (letter=='b')

thing is that the representation of the letters a-z are 97-122 and A-Z are 65-90, so if the case of the letter is important you need to pay attention to it.