View Compilation Error

0_0_30343486_13253.cpp: In constructor 'bign::bign()':
0_0_30343486_13253.cpp:13:45: error: 'memset' was not declared in this scope
     bign()          { memset(d, 0, sizeof(d)); len = 1; }
                                             ^
0_0_30343486_13253.cpp: In member function 'bign bign::operator=(const char*)':
0_0_30343486_13253.cpp:17:31: error: 'memset' was not declared in this scope
         memset(d, 0, sizeof(d)); len = strlen(num);
                               ^
0_0_30343486_13253.cpp:17:50: error: 'strlen' was not declared in this scope
         memset(d, 0, sizeof(d)); len = strlen(num);
                                                  ^