View Compilation Error

0_0_34488871_28650.cpp: In function 'int main()':
0_0_34488871_28650.cpp:14:28: error: 'memset' was not declared in this scope
    memset(a1, 0, sizeof(a1));
                            ^
0_0_34488871_28650.cpp:18:23: error: 'strlen' was not declared in this scope
    int len1 = strlen(a);
                       ^