View Compilation Error

0_0_20157213_1271.cpp: In function 'int main()':
0_0_20157213_1271.cpp:13:25: error: 'memset' was not declared in this scope
   memset(a, 0, sizeof(a));
                         ^
0_0_20157213_1271.cpp:14:17: error: 'strlen' was not declared in this scope
   len = strlen(s);
                 ^