How do I extract specific 'n' bits of a 32-bit unsigned integer in C?

Question

Could anyone tell me as to how to extract \'n\' specific bits from a 32-bit unsigned integer in C.

For example, say I want the first 17 bits of the 32-bit value;

Answer 1

If you need the X last bits of your integer, use a binary mask :

unsigned last8bitsvalue=(32 bit integer) & 0xFF
unsigned last16bitsvalue=(32 bit integer) & 0xFFFF

Answer 2

This is a briefer variation of the accepted answer: the function below extracts the bits from-to inclusive by creating a bitmask. After applying an AND logic over the original number the result is shifted so the function returns just the extracted bits. Skipped index/integrity checks for clarity.

uint16_t extractInt(uint16_t orig16BitWord, unsigned from, unsigned to) 
{
  unsigned mask = ( (1<<(to-from+1))-1) << from;
  return (orig16BitWord & mask) >> from;
}