Why do I get a different result for pi then what is listed in math.h?

[Richard Andrews]

Math.h defines pi as:
#define M_PI 3.1415926535897 9323846

Yet I get the fallowing result with the following source.

C:\BC5\BIN>read s pia.c
#include <stdio.h>
#include <math.h>

int main(void)
{

printf("Pi to 32 places is %.31f\n", M_PI);
return 0;
}

C:\BC5\BIN>pia
Pi to 32 places is 3.1415926535897 931200000000000 000

C:\BC5\BIN>

[weaknessforcats]

It makes no difference how many decimals are in the #define.

The value has to be converted to a double so you are limited by the number of decimals available in a double.

Since the #define has a value that's too long for a double so you get odd results for the part that doesn't fit.