Question

code one is:

int a = 0x42500000;
float *f = (float *)&a;    
printf("%f", *f);     //output 52.00000

code two is:

int a = 0x42500000;
float f = (float)a;    
printf("%f", f);        //output 0.00000

why code two output 0.00000,who can tell me why?

Answer 1

First snippet interprets the contents of the memory location of a as if it were float, without casting. Unless you really know what you are doing, you don’t want to do that, it’s almost always a mistake.

The second snippet casts the value of a to float, which should give you the same value as the int. It really does do that. Your code gives me 1112539136.000000. What compiler are you using and getting 0 there?