I have a function that converts me from any base to base 10 but the result is very long and it cannot be stored in an integer. Can someone explain me how should i use bignum lib so i can print result?

Depends on which bignum library you use. For example OpenSSL BigNum lib has functions:

 char *BN_bn2hex(const BIGNUM *a);
 char *BN_bn2dec(const BIGNUM *a);BN_bn2hex() and BN_bn2dec() return printable strings containing the hexadecimal and decimal encoding of a respectively. 
For negative numbers, the string is prefaced with a leading '-'. The string must be freed later using OPENSSL_free().

EDIT: fixed formatting.

Edited May 16, 201114 yr by kao

http://gmplib.org/

I am going to use this library. How should i do it?

You really don't want to search, do you?
/>http://gmplib.org/manual/Formatted-Output.html

ISO-C and most C++ compilers support 64bit integer (long long) and their unsigned equivalents. Maybe that's enough for your needs.

unsigned long long ul64 = 1111111122222222ULL;

Edited May 16, 201114 yr by Killboy