C and C++ program to perform various operations on strings

#include"iostream.h"
#include"conio.h"
#include"stdio.h"
void findlength()
{
 char str[30];
 int l=0;
 cout<<"\n Enter the string (size < =30) ";
 gets(str);
 while(str[l]!='\0')
 {
  l++;
 }
 cout<<"\n Length Of the given String is: "<< l<< endl;
}
void compare()
{
 char str1[30], str2[30];
 int l1=0,l2=0,i=0,flag=0;
 cout<<"\n Enter the string1 (size< =30) ";
 gets(str1);
 while(str1[l1]!='\0')
 {
  l1++;
 }
 cout<<"\n Enter the string2 (size< =30) ";
 gets(str2);
 while(str2[l2]!='\0')
 {
  l2++;
 }
 if(l2!=l1)
 {
  cout<<"\n Strings are not Equal ";
 }
 else
 {
  for(i=0;i< l1; i++ )
  {
      if(str1[i]!=str2[i])
      {
   flag=1;
   break;
      }
  }
  if(flag==1)
  {

   cout<< "\n Strings are not Equal ";
  }
  else
  {
   cout<< "\n Strings are Equal ";
  }
 }


}

void concat()
{
 char str1[30], str2[30];
 int l1=0,l2=0,i=0,flag=0;
 cout<<"\n Enter the string1 (size< =30 ) ";
 gets(str1);
 while(str1[l1]!='\0')
 {
  l1++;
 }
 cout<<"\n Enter the string2 (size< =30 ) ";
 gets(str2);
 while(str2[l2]!='\0')
 {
  l2++;
 }
 for(i=0;i < l2;i++)
 {
  str1[l1+i]=str2[i];
 }
 str1[l1+l2]='\0';
 cout<<"\n The concatenated String is: ";
 puts(str1);

}


void main()
{
 clrscr();
 cout<<" Enter your choice \n \t1.Find length of string\n\t"
 "2.Compare two Strings \n\t3.Concatenate two strings\n\t4.Exit \n";
 char ch;
 cin>> ch;
 do
 {
  if(ch=='1')
   findlength();
  if(ch=='2')
   compare();
  if(ch=='3')
   concat();
  cout<< "Enter your choice \n \t1.Find length of string\n\t"
 "2.Compare two Strings \n\t3.Concatenate two strings\n\t4.Exit \n";
 cin>> ch;

 }while(ch!='4');
 getch();
}

Source:  http://www.learncandcpp.com/2012/02/c-program-to-perform-all-operations-on.html