View Compilation Error

0_0_20493955_13095.cpp: In function 'int main()':
0_0_20493955_13095.cpp:17:29: error: 'memset' was not declared in this scope
         memset(n,0,sizeof(n));
                             ^
0_0_20493955_13095.cpp:19:27: error: 'strlen' was not declared in this scope
         int len=strlen(buf);
                           ^