CODEWITHSUNDEEP
clogic
Wang Liangwei
Wang Liangwei

Reputation: 59

Looping won't stop when reading user input

This code cannot stop looping even when I enter n or N.

What is causing this?

    char next = "";

    printf("Do u want continue\n");
    scanf("%c", &next);
    getchar();
    do
    {
        if (next=='y' ||next=='Y')
        {
            selection();
        }
        else
        {
            printf("invalid Please Enter again");
            scanf("%c", &next);
        }
    } while (next !='n'|| next!='N')

Upvotes: 3

Views: 172

Answers (4)

秦时明月
秦时明月

Reputation: 35

while (next !='n' || next!='N') is always true.

You can simply change it like this:

while (next !='n')

Then you input n, it stopped.

Upvotes: 0

Aaron Pool
Aaron Pool

Reputation: 489

Your while conditional will always evaluate to true. The input character will always be either NOT 'N' or NOT 'n'. Because it's only a single character, so it will always not be one of the two. You need you need to instead ensure that it's NEITHER of them. This is a logical AND check, rather than and OR check. So, instead, change that conditional to an AND, a.k.a next !== 'n' && next !== 'N', or, if you find using OR makes more sense, the following conditional is equivalent to the AND statement, through use of Boolean logic transformations !(next == 'n' || next == 'N').

Cheers!

Upvotes: 2

dbush
dbush

Reputation: 223699

The conditional (next !='n'|| next!='N') is always true.

If next is 'n' then next!='N' is true making the whole expression true. Similarly, if next is 'N' then next!='n' is true again making the whole expression true.

What you want here is to use a logical AND &&:

} while (next !='n' && next!='N')

Upvotes: 4

Jabberwocky
Jabberwocky

Reputation: 50778

Besides dbush's answer which is correct:

  • char next = ""; is wrong, it should be char next;
  • Don't use scanf but use only getchar, scanf is full of pitfalls.

Replace this:

char next;
...
scanf("%c", &next);
getchar();

with this:

int next;
...
next = getchar();

Upvotes: 1

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