What is the while equivelent to the default function in the switch statement??

**Thinlizzy76** · 11-14-2011

I want to make sure a user can't enter any characters except 0,1,2 or 3 using a while loop. how do i do it?

**hk_mp5kpdw** · 11-14-2011

You mean keep on looping until a character other than 0,1,2,3 is entered? I'd use a do-while loop... roughly:

Code:

do
{
    Get input from user.
    If input is not what you want then "break" from loop.
} while(1);

**MK27** · 11-14-2011

You can't prevent them without using some special library, but you can do something like this:

Code:

	int x = -1;
	while (x < 0 || x > 3) {
		printf("Enter a number between 0 and 3: ");
		scanf("%d", &x);
	}

**Thinlizzy76** · 11-14-2011

sorry i meant to say that if a person enters a character other than 0,1,2,3 that an error will display. is there any way at all to do this with a while or do while statement?

**Tclausex** · 11-14-2011

You make the while test for true if any value other than 0,1,2, or 3 are entered and within the while loop you output the error and reprompt.

**Thinlizzy76** · 11-14-2011

Originally Posted by Tclausex

You make the while test for true if any value other than 0,1,2, or 3 are entered and within the while loop you output the error and reprompt.

How exactly would i do that??? here's the code:

Code:

while(i!=5)
    {
       
           
           
                printf("2011 Presidential Election \n");
            
                system("pause");
               
                printf("\nPlease Enter a vote for cand1 \n");
                printf("Enter 1 for first choice \n");
                printf("Enter 2 for 2nd choice \n");
                printf("Enter 3 for 3rd choice \n");
                printf("Enter 0 for no vote \n");
                        
                scanf("%d",&mg[j]);
                
                printf("Please Enter a vote for cand2\n");
                printf("Enter 1 for first choice \n");
                printf("Enter 2 for 2nd choice \n");
                printf("Enter 3 for 3rd choice \n");
                printf("Enter 0 for no vote \n");
                        
                scanf("%d",&da[j]);
                
                printf("Please Enter a vote for cand3\n");
                printf("Enter 1 for first choice \n");
                printf("Enter 2 for 2nd choice \n");
                printf("Enter 3 for 3rd choice \n");
                printf("Enter 0 for no vote \n");
                        
                scanf("%d",&no[j]);
                
                printf("Please Enter a vote for cand4 \n");
                printf("Enter 1 for first choice \n");
                printf("Enter 2 for 2nd choice \n");
                printf("Enter 3 for 3rd choice \n");
                printf("Enter 0 for no vote \n");
                        
                scanf("%d",&gal[j]);
                
                printf("Please Enter a vote for cand5 \n");
                printf("Enter 1 for first choice \n");
                printf("Enter 2 for 2nd choice \n");
                printf("Enter 3 for 3rd choice \n");
                printf("Enter 0 for no vote \n");
                        
                scanf("%d",&hig[j]);
                
                printf("Please Enter a vote for cand 6 \n");
                printf("Enter 1 for first choice \n");
                printf("Enter 2 for 2nd choice \n");
                printf("Enter 3 for 3rd choice \n");
                printf("Enter 0 for no vote \n");
                        
                scanf("%d",&dav[j]);
                
                printf("Please Enter a vote for cand7 \n");
                printf("Enter 1 for first choice \n");
                printf("Enter 2 for 2nd choice \n");
                printf("Enter 3 for 3rd choice \n");
                printf("Enter 0 for no vote \n");
                        
                scanf("%d",&mit[j]);
                
                
                
                printf("\n Thank you for voting!! \n");
                
               
                
                system("pause");
              
                (i++);
                 j++;
                
               system("cls");    
              
              
              
               
    }

**Tclausex** · 11-14-2011

MK27 handed you the code for test.

Looking at the code you posted, you'll want to create a function to read in the user's answer.

**Thinlizzy76** · 11-14-2011

how would i do this??sorry i'm such a noob.

**Tclausex** · 11-14-2011

Well, if you don't know functions yet, leave it for another day. Just repeat the while loop code for each vote, changing the variable you're testing to the appropriate one for that vote.

Easiest approach for you would be to insert the while loop after the scanf(). If the user's data is bad, you'll go into the loop, otherwise it will skip it and go to next vote. Inside the loop, print your error, print a re-prompt for the user, and scanf() again. The loop will continue until the user inputs good data. Then you move on to the next vote.

**~~CommonTater~~** · 11-14-2011

Here ya go... a voting machine in less than 60 lines...
I know it's not exactly what you want (wouldn't post it if it was)...
but it demonstrates the principles you're interested in...

Code:

// the voting machine example
// to quit enter a q at the "Press Enter to vote" prompt

#include <stdio.h>
#include <conio.h>  // not standard C99

#define CANDS 5     // number of candidates

int main (void)
  { int votes[CANDS] = {0};
    char candidate[CANDS][32]; 
    int i;
    char vote, quit = 0; 

    // get candidate names
    for (i = 0; i < CANDS; i++)
      do
        printf("Enter the last name of candiate #%d : ", i + 1);
      while(scanf(" %s",candidate[i]) < 1);

    // let the voting begin
    while(quit != 'q')
      { clrscr();         // not standard C99
      
        printf("Your candidates are ...\n");
        for (i = 0; i < CANDS; i++)
          printf("%d) %s\n",i + 1, candidate[i]);
        do
          {
            printf("Your choice (1 to %d) :", CANDS);
            scanf(" %c",&vote);
            vote -= '1';
          }
        while((vote < 0) || (vote >= CANDS));

        // register the vote
        votes[vote]++;

        // prompt next voter
        clrscr();         // not standard C99
        printf("Next voter, press enter to vote :"); 
        while(getchar() != '\n');
        quit = getchar();
      }
    // display results
    clrscr();             // not standard C99
    printf("The voting results are...\n");
    for (i = 0; i < CANDS; i++)
      printf("%s\t\t%d\n",candidate[i],votes[i]);

    printf("\n\n Have a nice day!\n");
    return 0;
  }

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