Swap bits in a number in C [duplicate]

Answer 1

My skills in this area are new and therefore unproven so if I'm wrong then I learn something new, which is at least a part of the point of Stack Overflow.

Would a bitmask and XOR work also?

Like so?

var orginal=
var mask =00001110 //I may have the mask wrong
var value=1011 1110
var result=value^mask;

I might be misunderstanding things, forgive me if I've screwed up entriely.

Answer 2

unsigned char c;

c = ((c & 0xf0) >> 4) | ((c & 0x0f) << 4);

Answer 3

There's no need for a temporary variable, something like this should do it:

x = ((x & 0xf) << 4) | ((x & 0xf0) >> 4);

There is a potential pitfall with this depending on the exact type of x. Identification of this problem is left as an exercise for the reader.