C

float one(void)
{
    const int n = 24; // magic number
    float x = 0.5f;
    float y = x;
    int i;

    for (i = 0; i < n; ++i)
    {
        x *= 0.5f;
        y += x;
    }
    return y;
}

float one(void)
{
    const int n = 24; // magic number
    float x = 0.5f;
    float y = x;
    int i;

    for (i = 0; i < n; ++i)
    {
        x *= 0.5f;
        y += x;
    }
    return y;
}