View Compilation Error

0_0_37236453_6736.cpp: In function 'int main()':
0_0_37236453_6736.cpp:5:15: error: 'scanf' was not declared in this scope
  scanf("%d",&n);
               ^
0_0_37236453_6736.cpp:6:10: error: 'getchar' was not declared in this scope
  getchar();
          ^
0_0_37236453_6736.cpp:10:29: error: 'memset' was not declared in this scope
   memset(str2,0,sizeof(str2));
                             ^
0_0_37236453_6736.cpp:14:12: error: 'gets' was not declared in this scope
   gets(str1);
            ^
0_0_37236453_6736.cpp:16:19: error: 'strlen' was not declared in this scope
   len1=strlen(str1);
                   ^
0_0_37236453_6736.cpp:27:19: error: 'strcat' was not declared in this scope
   strcat(str2,str4);
                   ^
0_0_37236453_6736.cpp:30:12: error: 'puts' was not declared in this scope
   puts(str2);
            ^