CODEWITHSUNDEEP
cloopswhile-loop
user6913230
user6913230

Reputation:

Slight issue with Do While Loop

So I am writing a basic program that asks the user to input a number and the loop will continue until they enter a certain number. (25). Afterward the program will add up all of the numbers they inputted. The issue is when I type the exit number, the loop doesn't exit, and I'm not sure why. 

double userNum = 0;
double sum = 0;

do {
    printf("Please enter a number you would like to add [Enter 25 to exit at any time]:\n");
    scanf("%f", &userNum);
    sum = sum + userNum;
} while (userNum != 25); 

printf("The sum of all the numbers you entered:%f\n", sum);

Also Im not sure the sum will calculate properly as Ive never been able to exit the loop.

Upvotes: 0

Views: 71

Answers (3)

Justin Cole
Justin Cole

Reputation: 1

You are wanting to use a sentinel controlled loop (25 being your sentinel). Here is what I would write:

    #include <stdio.h>


    int main()
    {
        double userNum = 0;
        double sum = 0;

        while ( userNum != 25 ) { //sentinel controlled loop

        puts("Please enter a number you would like to add [Enter 25 to exit                at any time]:"); // puts automatically inputs a newline character
        scanf("%lf", &userNum); // read user input as a double and assign it to userNum
        sum = sum + userNum; // keep running tally of the sum of the numbers

        if ( userNum == 25 ) { // Subtract the "25" that the user entered to exit the program
        sum = sum - 25;
        } // exit the if
      } // exit while loop

        printf("The sum of all the numbers you entered:%lf\n", sum);

     } // exit main

OR, you can stick with do...while:

    // Using the do...while repetition statement
    #include <stdio.h>

    // function main begins program execution
    int main( void )
    {
       double userNum = 0; // initialize user input
       double sum = 0; //initialize sum as a DOUBLE

       do {                                               
        puts("Please enter a number you would like to add [Enter 25 to exit at any time]:"); // puts automatically inputs a newline character
        scanf("%lf", &userNum); // read user input as a double and assign it to userNum
        sum = sum + userNum; // keep running tally of the sum of the numbers


        if ( userNum == 25 ) { // Subtract the "25" that the user entered to exit the program
        sum = sum - 25;
        } // end if statement
       } while ( userNum != 25 ); // end do...while   

       printf("The sum of all the numbers you entered:%lf\n", sum);

    } // end function main

Upvotes: 0

user3121023
user3121023

Reputation: 8286

Consider using fgets for input and parse the value with sscanf. With this you could enter done or exit to terminate the loop instead of 25. The format for scanning a double is %lf.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main( void)
{
    char input[99] = "";
    double userNum = 0;
    double sum = 0;
    while ( 1) {
        printf("Please enter a number you would like to add [Enter 25 to exit at any time]:\n");
        if ( ( fgets ( input, sizeof ( input) , stdin))) {
            if ( strcmp ( input, "25\n") == 0) {//could use exit, done ... instead of 25
                break;
            }
            if ( ( sscanf(input, "%lf", &userNum)) == 1) {//sscanf successful
                sum = sum + userNum;
            }
        }
        else {
            break;//fgets failed
        }
    }
    printf("The sum of all the numbers you entered:%f\n", sum);

    return 0;
}

Upvotes: 1

Emile P.
Emile P.

Reputation: 3962

You're using the wrong datatype, go with integers instead:

int userNum = 0;
int sum = 0;
do {
    printf("Please enter a number you would like to add [Enter 25 to exit at any time]:\n");
    scanf("%d", &userNum);
    sum = sum + userNum;
} while (userNum != 25);
printf("The sum of all the numbers you entered:%d\n", sum);

Upvotes: 0

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