What is the best way to set a particular bit in a variable in C

Question

Consider a variable unsigned int a; in C.

Now say I want to set any i'th bit in this variable to '1'.

Note that the variable has some value. So a=(1<<i) will not work.

a=a+(1<<i) will work,but I am looking for the fastest way. Anything??

Answer 1

Bitwise or it. e.g. a |= (1<<i)

Answer 2

Some useful bit manipulation macros

#define BIT_MASK(bit)             (1 << (bit))
#define SET_BIT(value,bit)        ((value) |= BIT_MASK(bit))
#define CLEAR_BIT(value,bit)      ((value) &= ~BIT_MASK(bit))
#define TEST_BIT(value,bit)       (((value) & BIT_MASK(bit)) ? 1 : 0)