why the output of float a=1/2; is 0?

Answer 1

Because 1 and 2 are integer values so it gives an integer output. You need to typecast it to get a float output. For eg-

float a = (float) 1/2; OR
float a = 1.0f/2.0f;

Answer 2

or simply float a = 1/2.0; will do