View Compilation Error

0_0_35307262_24919.cpp: In function 'int main()':
0_0_35307262_24919.cpp:14:27: error: 'memset' was not declared in this scope
   memset(a1, 0, sizeof(a1));
                           ^
0_0_35307262_24919.cpp:18:22: error: 'strlen' was not declared in this scope
   int len1 = strlen(a);
                      ^