Help with a simple loop...

**Optimus Prime** · 11-10-2006

Code:

#include <stdio.h>
main()
{
      int option ;
      int pin ;
      int pindef ;
      int exit ;
      pin = 1234 ;
      
      
      
     while ( exit //PROBLEM HERE!!!
     {
      printf( "Welcome to the main menu,please chose from the following options...:\n\n" ) ;//menu greting
      printf( "1.      Enter PIN and verify correct.\n\n" ) ;//option 1
      printf( "2.      Change PIN.\n\n" ) ;//option 2
      printf( "3.      Display the number of times the PIN was entered:\n (i) Successfully \n(ii) Incorrectly\n\n" ) ;//option 3
      printf( "4.      Set maximum number of attempts to enter correct PIN.\n\n" ) ;//option 4
      printf( "5.      Exit Program.\n\n" ) ;//option 5
      
      
    
      
      
      printf( "Please chose an option between 1 - 5:\n") ;
      scanf( "%d",&option) ;//option input
      
      switch (option)       //begining of switch statement
      {
            
            
            
            case 1:
                 printf( "Please enter you pin\n") ; // begining of option 1
                 scanf("%d",&pin) ; //scan PIN
      
                 if ( pin == 1234 ) // loop if pin is entered correctly
                 printf( "This is the correct PIN\n" ) ;
                 printf( "Press 3 to exit\n" ) ;
                 scanf( "%d",&exit) ;
        
        if ( pin !=1234 )
        
        while ( pin != 1234)//loop if pin is entered incorrectly
        {
             printf( "This is not the correct PIN\n" ) ;
             printf( "Please re - enter your pin\n" ) ;
             scanf( "%d",&pin ) ; //re scan pin
             
             printf( "This is not the correct PIN\n" ) ;
             printf( "Please re - enter your pin.You have one attempt left\n" ) ;
             scanf( "%d",&pin ) ; //re scan pin
             
             printf( "This is not the correct PIN\n" ) ;
             printf( "You must re - start Program\n" ) ;
             scanf( "%d",&pin ) ; //re scan pin
             printf( "Press 3 to exit\n" ) ;
                 scanf( "%d",&exit) ;
             
             
             break ;
        }// end while
            break;  //end of option 1
            
            
            
            
            
            case 2:
                 printf( "You have chosen option 2" ) ;
              break ;
                 
            case 3:
                 printf( "You have chosen option 3" ) ;
                 break ;
                 
            case 4:
                 printf( "You have chosen option 4" ) ;
                 break ;
                 
            case 5:
                 printf( "You have chosen option 5" ) ;
                 break ;
            
             }//end switch
      
      }//end while
      
      
      
      
      
}//end main

basically i need the program to loop back to the main menu after i have interacted with an option,i did it earlier on in college but cant do it now

any help would be appreciated!

**manutd** · 11-10-2006

For one your while brackets are not closed off:

Code:

while ( exit

Should be

Code:

while (exit)

Also it should be:

Code:

while(exit != 3)

if I'm reading your code correctly.

**Optimus Prime** · 11-10-2006

ah i know its not closed off....i left it open because i didnt know what to do next...i did what you said,but its not looping!

**manutd** · 11-10-2006

Your if needs brackets:

Code:

if ( pin !=1234 )
{
 
        while ( pin != 1234)//loop if pin is entered incorrectly
        {
             printf( "This is not the correct PIN\n" ) ;
             printf( "Please re - enter your pin\n" ) ;
             scanf( "%d",&pin ) ; //re scan pin
 
             printf( "This is not the correct PIN\n" ) ;
             printf( "Please re - enter your pin.You have one attempt left\n" ) ;
             scanf( "%d",&pin ) ; //re scan pin
 
             printf( "This is not the correct PIN\n" ) ;
             printf( "You must re - start Program\n" ) ;
             scanf( "%d",&pin ) ; //re scan pin
             printf( "Press 3 to exit\n" ) ;
                 scanf( "%d",&exit) ;
 
 
             break ;
        }// end while
}//End if

Also, initialize exit:

Code:

int exit = 0;

Or better yet, enum a bool type and use that.

**Optimus Prime** · 11-10-2006

kinda works now....its just not looping option2..

**manutd** · 11-10-2006

What do you mean? What is not working? Selecting option 2? DId you forget the closing bracket of the if statement?

**Salem** · 11-10-2006

Choose another name rather than exit, since there is also a function of the same name.

**dwks** · 11-10-2006

Code:

        while ( pin != 1234)//loop if pin is entered incorrectly
        {
             printf( "This is not the correct PIN\n" ) ;
             printf( "Please re - enter your pin\n" ) ;
             scanf( "%d",&pin ) ; //re scan pin
             
             printf( "This is not the correct PIN\n" ) ;
             printf( "Please re - enter your pin.You have one attempt left\n" ) ;
             scanf( "%d",&pin ) ; //re scan pin
             
             printf( "This is not the correct PIN\n" ) ;
             printf( "You must re - start Program\n" ) ;
             scanf( "%d",&pin ) ; //re scan pin
             printf( "Press 3 to exit\n" ) ;
                 scanf( "%d",&exit) ;
             
             
             break ;
        }// end while

That won't do what you want it to do. I read somewhere that some programmers think that as soon as a while loop's condiiton is false, the loop will end. I guess you have this impression. Well, a while loop only exits when execution of the program gets to the to of the loop and the condition is false. http://www.cprogramming.com/tutorial/c/lesson3.html

**manutd** · 11-10-2006

aka add:

Code:

printf( "This is not the correct PIN\n" ) ;
printf( "Please re - enter your pin\n" ) ;
scanf( "%d",&pin ) ; //re scan pin
if (pin != 1234)
{
         continue;
}

**dwks** · 11-10-2006

I would do it like this myself:

Code:

int x;

for(x = 0; x < 3 && pin != 1234; x ++) {
    printf( "This is not the correct PIN\n" ) ;
    printf( "Please re - enter your pin\n" ) ;
    scanf( "%d",&pin ) ; //re scan pin
}

Or something like that.

BTW, you don't need to set pin at the beginning of the program . . . but if you do, I wouldn't set it to the correct value.

Maybe -1 or INT_MIN or something.

**manutd** · 11-10-2006

It's a matter of preference. Generally I would use your approach, I just wanted to keep the code as close to his original as possible (adding what amounts to 2 lines).

**dwks** · 11-10-2006

I don't see how a continue would keep the code in its original condition . . . a break would be better.

**quzah** · 11-10-2006

Originally Posted by manutd

Your if needs brackets:

Code:

if ( pin !=1234 )
{
 
        while ( pin != 1234)//loop if pin is entered incorrectly
        {

Purely optional, though it is good practice. The if will bind to the nearest appropriate statement, as will for, do, while. Thus:

Code:

if( x == y )
    while( x < z )
        do
            for( ; z-- ; )
                printf( "%d", y );
        while( z = y-- );

While incredibly ugly, it's perfectly legal.

Quzah.

**Optimus Prime** · 11-10-2006

ok you have to remember i NEW to all of this lol...if someone could write a really small code giving the user a choice of 2 options,and when the user finishes wit an option it loops back to the menu,this would be great help.oh and using a while loop

**dwks** · 11-10-2006

It was explained reasonably well in your other thread. The basic structure looks like this:

Code:

while(!quit) {
    scanf("%i", &menu);

    switch(menu) {
    case N:
        /* ... */
        break;
    default:
        /* ... */
        break;
    }
}

Anyway, you don't seem to be having too much trouble with that part . . . it's the pin part that needs working on.

[edit]

While incredibly ugly, it's perfectly legal.

http://cboard.cprogramming.com/showthread.php?t=85193 [/edit]

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