1#define FIXED_TYPE_SIZE long
2#define FIXED_POINT_FRACTIONAL_BITS 16          // 32 bits = 16.16
3
4
5// Choose what floating point values to use as REALs
6typedef FIXED_TYPE_SIZE F_REAL; // (Fixed Point Real Number)
7
8
9// Convert float to fixed-point
10F_REAL RTOFIX(float value) {
11    return (F_REAL)(value * (1 << FIXED_POINT_FRACTIONAL_BITS));
12}
13
14// Convert fixed-point to float
15float FIXTOR(F_REAL value) {
16    return (float)value / (1 << FIXED_POINT_FRACTIONAL_BITS);
17}
18
19// Convert integer to fixed-point
20F_REAL ITOFIX(int value) {
21    return value << FIXED_POINT_FRACTIONAL_BITS;
22}
23
24// Convert fixed-point to integer
25int FIXTOI(F_REAL value) {
26    return value >> FIXED_POINT_FRACTIONAL_BITS;
27}
28
29// Multiplication of two fixed-point numbers
30F_REAL F_REAL_MUL(F_REAL a, F_REAL b) {
31    return (F_REAL)(((long long)a * b) >> FIXED_POINT_FRACTIONAL_BITS);
32}
33
34// Division of two fixed-point numbers
35F_REAL F_REAL_DIV(F_REAL a, F_REAL b) {
36    return (F_REAL)(((long long)a << FIXED_POINT_FRACTIONAL_BITS) / b);
37}

1float a = 5.f;
2F_REAL b = RTOFIX(a);
3float c = FIXTOR(b);
4
5printf("c = %f\n", c);
6
7Output is: c = 0.000000 !!!
8and should be ~5.000000