View Compilation Error

0_0_23354085_8335.cpp: In function 'int main()':
0_0_23354085_8335.cpp:6:42: error: 'memset' was not declared in this scope
     #define clear(a) memset(a,0,sizeof(a))  
                                          ^
0_0_23354085_8335.cpp:65:13: note: in expansion of macro 'clear'
             clear(sum);  
             ^