View Compilation Error

0_0_33804227_18192.cpp: In function 'bool prime(int)':
0_0_33804227_18192.cpp:8:29: error: 'sqrt' was not declared in this scope
  for (int i = 2; i <= sqrt(n); i++)
                             ^
0_0_33804227_18192.cpp: In function 'int main()':
0_0_33804227_18192.cpp:14:27: error: 'memset' was not declared in this scope
  memset(a, false, sizeof a);
                           ^