View Compilation Error

0_0_37428472_28478.cpp:1:9: error: #include expects "FILENAME" or <FILENAME>
 #include
         ^
0_0_37428472_28478.cpp:2:9: error: #include expects "FILENAME" or <FILENAME>
 #include
         ^
0_0_37428472_28478.cpp: In function 'int a(char*, char*)':
0_0_37428472_28478.cpp:8:22: error: 'strlen' was not declared in this scope
 for(i=0;i<=strlen(ch1);++i)
                      ^
0_0_37428472_28478.cpp:10:28: error: 'abs' was not declared in this scope
  return abs(ch1[i] - ch2[i]);
                            ^
0_0_37428472_28478.cpp: In function 'int main()':
0_0_37428472_28478.cpp:16:5: error: 'cin' was not declared in this scope
     cin >> ch1 >> ch2;
     ^
0_0_37428472_28478.cpp:17:5: error: 'cout' was not declared in this scope
     cout << a(ch1, ch2) << endl;
     ^
0_0_37428472_28478.cpp:17:28: error: 'endl' was not declared in this scope
     cout << a(ch1, ch2) << endl;
                            ^