Declare varible in scanf or printf

Question

1.50/5 (2 votes)

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C

#include<stdio.h>

int main ()
{
	int c,n,fact = 1;
	printf("Enter a number to calculate it's factorial\n");
	scanf("%d", &n);
	for (c=1; c <= n; c++);
	fact = fact *c;
	printf("The factorial of %d	= %d", n, fact);
	
	printf("Do you want to continue?\n");
	scanf("%c", &(char){ch} );
	if (ch == 'y' || ch == 'Y')
	continue;
	else
	break;
	return(0);
	
}

In the above program I have declared ch as char within scanf but it is not working can any one help.

Posted 3-Feb-16 6:00am

gschahal

Updated 3-Feb-16 6:07am

Dave Kreskowiak

v2

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3 solutions

Solution 2

Um...what did you expect that to do?

C#

scanf("%c", &(char){ch} );
if (ch == 'y' || ch == 'Y')
   continue;

That doesn't "declare" anything - and if it did (which it can't, it's not allowed by the C syntax), it wouldn't logically be available outside the call to scanf. So the subsequent line wouldn't be able to access it anyway.
And the semicolon at the end of the for loop doesn't help either...
Try this instead:

C#

int main ()
{
    int c,n,fact = 1;
    char ch[100];
    printf("Enter a number to calculate it's factorial\n");
...
    scanf("%c", ch );
    if (ch[0] == 'y' || ch[0] == 'Y')
    {
        continue;
    }
    else
    {
        break;
    }
    return(0);
}

Except you'll need a loop round most of it for the continue / break logic to work!

Posted 3-Feb-16 6:15am

OriginalGriff

Comments

Sergey Alexandrovich Kryukov 3-Feb-16 12:24pm

Sure, explained more clearly, a 5.
—SA

gschahal 3-Feb-16 12:39pm

WHat is a 5?

Sergey Alexandrovich Kryukov 3-Feb-16 12:45pm

Excellent mark.
—SA

gschahal 3-Feb-16 12:32pm

#include<stdio.h>

int main ()

{
int c,n,fact = 1;
char ch;

while(1)
{

printf("Enter a number to calculate it's factorial\n");
scanf("%d", &n);
for (c=1; c <= n; c++);
fact = fact *c;
printf("The factorial of %d = %d", n, fact);

printf("Do you want to continue?\n");
scanf("%c", &ch);
if (ch == 'y' || ch == 'Y')
continue;
else
break;
}
return(0);
}

I tried changing it to the above one. But when I tried as per your solution it didn't worked

OriginalGriff 3-Feb-16 12:42pm

Read what I said: you haven't fixed both of the other two problems, and you didn't type what I did anyway!
And please - indent your code! It will make your life a whole lot easier... :laugh:
And as a beginner, always - but always - use curly brackets to "delimit" a block, even if it's only one line. It may seem like more work, but it can save you a lot of hair pulling when you make the inevitable mistake...

Andreas Gieriet 3-Feb-16 13:25pm

Your for (...); loop is broken!
What is the body of your loop? A semi-colon = empty statement.
What you get is probably fact = n+1.
Cheers
Andi

Solution 3

The way you made it suffer your exquisite programming language fills me with the urge to...
Try:

C

#include<stdio.h>

int main ()
{
	int c,n,fact = 1;
	char ch;
	do
	{
		printf("Enter a number to calculate it's factorial\n");
		while (scanf("%d", &n) != 1)
		{
			printf("please try again\n");
			fflush(stdin);
		}
		fflush(stdin);
		for (c=1; c <= n; c++)
		{
			fact = fact * c;
		}

		printf("The factorial of %d	is %d\n", n, fact);
	
		printf("Do you want to continue?\n");
		scanf("%c", &ch);
	}  while (ch == 'Y' || ch == 'y');
	return 0;
}

Posted 3-Feb-16 7:43am

CPallini

Comments

Aescleal 3-Feb-16 16:03pm

Have 5 for the allusion.

CPallini 4-Feb-16 11:48am

Thank you. :-)

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Dave Kreskowiak · Accepted Answer · 2016-02-03T06:08:00

Solution 1

Yeah, you can't do that. This is C, not java.

ch has to be declared outside of a function call.

Besides, why would you want to declare a variable inside the scanf call? It's scope, if this worked at all, would be limited to only the code inside the braces in the scanf call. The variable wouldn't exist outside of that call and you couldn't be used in the if statement immediately after that.

Posted 3-Feb-16 6:08am

Dave Kreskowiak

Updated 3-Feb-16 6:15am

v2

Comments

Sergey Alexandrovich Kryukov 3-Feb-16 12:23pm

Sure, a 5.
—SA

gschahal 3-Feb-16 12:26pm

SO that means there is no other way in C to declare variable? We will have to define it at the top

Dave Kreskowiak 3-Feb-16 15:19pm

It doesn't have to be at the top. It just has to be before you use the variable. You can put the declaration immediately before the call to scanf for all the compiler cares.