View Compilation Error

0_0_34845242_29373.cpp: In function 'int main()':
0_0_34845242_29373.cpp:12:34: error: 'memset' was not declared in this scope
  memset(a, 0, 1000 * sizeof(char));
                                  ^
0_0_34845242_29373.cpp:17:15: error: 'strlen' was not declared in this scope
   n = strlen(a);
               ^