c - How can I convert a binary number (32 bit) to a decimal number? -

i've seen various programs can convert given decimal floating point number, binary in ieee 754 format.
now, given binary number, how can program in c convert floating point number?

example:

input:  01000001010010000000000001111111 output: 12.50012111663818359375 

i'm assuming have binary representation string.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h>  void setbit(uint32_t* f, int i) {     uint32_t mask = ((uint32_t)1) << i;     *f |= mask; }  float readfloat(const char* bits) {     assert(strlen(bits)==8*sizeof(float));     assert(sizeof(uint32_t)==sizeof(float));     float f = 0;     int size = strlen(bits);     (int = 0; < size; i++) {         int bit = bits[size-i-1]- 0x30;         if (bit) {             setbit((uint32_t*)&f, i);         }     }     return f; }  int main(int argc, char *argv[]){     const char* bits = "01000001010010000000000001111111";     float f = readfloat(bits);     printf("%s -> %.20f", bits, f); } 

gives

01000001010010000000000001111111 -> 12.50012111663818359375