View Compilation Error

0_0_29666201_27268.cpp: In function 'int main()':
0_0_29666201_27268.cpp:5:38: error: 'memset' was not declared in this scope
 #define mem(a) memset(a, 0, sizeof(a))
                                      ^
0_0_29666201_27268.cpp:35:3: note: in expansion of macro 'mem'
   mem(c); 
   ^