Lower case to upper case

Question

How to convert lower case ASCII char into upper case using a bitmask (no -32 allowed)?

I'm not asking for solving my homework, only some hints.

Thanks

Answer 1

As you state "(no -32 allowed)", I guess you know that the difference between lower case characters and upper case characters is 32. Now convert 32 to its binary representation, there's only one bit set. After that, work out a way to use a bit mask to switch the bit.

Answer 2

Think about the differential between lower and upper case (0x20) and then apply the appropriate mask to your value

XOR to get lower from upper or upper from lower