View Compilation Error

0_0_17918972_14121.cpp: In function 'int main()':
0_0_17918972_14121.cpp:8:36: error: 'memset' was not declared in this scope
 #define mem(a) memset(a,0,sizeof(a))
                                    ^
0_0_17918972_14121.cpp:16:3: note: in expansion of macro 'mem'
   mem(a);
   ^