View Compilation Error

0_0_36507604_11020.cpp: In function 'int main()':
0_0_36507604_11020.cpp:5:36: error: 'memset' was not declared in this scope
 #define mem(x) memset(x,0,sizeof(x))
                                    ^
0_0_36507604_11020.cpp:49:9: note: in expansion of macro 'mem'
         mem(mmp);
         ^