View Compilation Error

0_0_29900151_17373.cpp: In function 'int main()':
0_0_29900151_17373.cpp:5:2: error: 'cin' was not declared in this scope
  cin.getline(a,100000);
  ^
0_0_29900151_17373.cpp:6:12: error: 'strlen' was not declared in this scope
  n=strlen(a);
            ^
0_0_29900151_17373.cpp:7:2: error: 'cout' was not declared in this scope
  cout<<n<<endl;
  ^
0_0_29900151_17373.cpp:7:11: error: 'endl' was not declared in this scope
  cout<<n<<endl;
           ^