Thread: While loop with multiple characters

First off - this is a homework problem, and I do not expect you guys to do the coding for me

However, I do need some general hints as to how I should format this problem.

Here is the problem assigned to me
"To gain entrance to a secret area you often need a secret password consisting a sequence of alphanumeric characters that must be entered in a specified order. Create a program that reads in characters until the user enters the correct two character sequence (cs) to open the door. "

Note: we have not covered strings or arrays, so we can take those options off the board right not.

I figured the best way to accomplish this task was to use a while loop, but I am encountering some troubles trying to figure out exactly how to accomplish it.

I have created a program that correctly uses a while loop with a character but I cannot get it to work for 2 characters.

Code:

#include <stdio.h>

int main()
{

    puts("Please enter password now");
    
    while(getchar() != 'c')
    
    printf("Incorrect password try again");
    
    system("pause");
}

Its a small start, but this is something I don't have much experience with.

Thanks in advance,

AB

Hello arctic_blizzard!

To gain entrance to a secret area you often need a secret password consisting a sequence of alphanumeric characters that must be entered in a specified order. Create a program that reads in characters until the user enters the correct two character sequence (cs) to open the door.

Did you see the main problem in the bold text?

You can get two character sequence by doing this:

Code:

char c1, c2;
c1 = getchar();
c2 = getchar();

So, check the characters inputted by user are correct or not:

Code:

if(c1 == 'a' && c2 == 'b')
{
   printf("Correct password.");
}
else
{
   printf("Incorrect password.");
}

And you can make your program request to the user repeatly:

Code:

for(;;)
{
   //request to the user
}

At last, if we combine them, should be look like this:

Code:

for(;;)
{
   char c1, c2;

   printf("Please enter the password: ");

   c1 = getchar();
   c2 = getchar();

   if(c1 == 'a' && c2 == 'b')
   {
      printf("Correct password.");
      break; //Exit loop
   }
   else
   {
      printf("Inorrect password.");
   }
}

Granted - this program works beautifully, but I am pretty sure the professor was looking for us to create a program using loops.

I have tried to build on this code, using loops instead of the if else statement, but am still encountering problems. For one - the program issues success even if only one of the variables is met, and my printf statement shows no matter what the outcome it - is there a way to display different statements depending on success/failure using the while statement?

Code:

#include <stdio.h>

int main()

{
   char pass1, pass2;

   printf("\nPlease enter your password now:");

   while(pass1!='c' && pass2!='s')
   {
      pass1=getchar();
      pass2=getchar();
      printf("statement");
}
    system("pause");
}

Thank you for your posts,

AB

Quite simple...

Code:

int first = 1;

while(pass1 != 'c' && pass2 != 's')
{
   printf("%s", (first ? "" : "Incorrect password."));
   first = 0;
   pass1=getchar();
   pass2=getchar();
}
printf("Correct password.");

Ok, I am bound and determined to get this one right.

I tried a new tactic - using a do while loop. I can get the program to successfully run when I input 1 correct letter, but is there a way to get it to only accept the correct sequence of letters?

Code:

#include <stdio.h>

int main()
{
    char Pass;
    do
      {
                  printf("Enter password:");
                  scanf("%s", &Pass);
      } 
      while(Pass != 'a');
system("pause");
return 0;
}

the program works fine, and asks for the password again if 'g' is not entered
but, how can I make this work if the password is two letters (say 'ab')

I have tried
while(Pass != 'a' && Pass != 'b');
but the program never successfully completes, it just keeps looping
I have also tried
while(Pass != 'ab');
but I get the same result.

What am I missing?

-AB

OK, I think I finally have it!

Thanks to everyone for the suggestions, I used many of them.

Here is my working code, take a look at it, and see if there is anything wrong with it.

Code:

#include <stdio.h>

int main()
{
     int Pass = 1;
     char Pass1;
     char Pass2;

     while (Pass)
     {
           printf("Please enter your password: ");
           Pass1=getchar();
           Pass2=getchar();
           if (Pass1!='g' || Pass2!='f');
           else 
  
           Pass = 0;
           }
system("pause");
return 0;
}

Cheers,
~AB

it would work for any characters that you define in the equation.

I was just using random letters

I am using Dev C++ v 4.9.9.2 using its default compiler (GCC I believe).

Is there a better program I should be using?

I have Microsoft Visual C++ 2008, would that be a better program to use?
Can you still write C code in VC++?