View Compilation Error

0_0_29937463_25218.cpp: In function 'int main()':
0_0_29937463_25218.cpp:16:10: error: 'a' was not declared in this scope
   memset(a, 0, sizeof(a));
          ^
0_0_29937463_25218.cpp:16:25: error: 'memset' was not declared in this scope
   memset(a, 0, sizeof(a));
                         ^