value of pi (π)

==> In term of fractions: 
22/7,
333/106,
355/113 = 3.1415929203539823008849557522124,
103993/33102, 
104348/33215, 
208341/66317,
312689/99532,
833719/265381,
1146408/364913,
4272943/1360120,
...
...
428224593349304/136308121570117, ...

==> From GNU's math.h header file:
# define M_PI       3.14159265358979323846  /* pi */

Reference:
http://numbers.computation.free.fr/Constants/Pi/piApprox.html
http://c2.com/cgi/wiki?ValueOfPi