C - why scanf("%d",&n) and gets(string) don't work together?

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why scanf("%d",&n) and gets(string) don't work together?

Total Answers and Comments: 1

Last Update: September 18, 2007 Asked by: pbchaudhari

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September 18, 2007 02:49:03

baseersd

Member Since: June 2007 Contribution: 34

RE: why scanf("%d",&n) and gets(string) don't work tog...

This is a general problem of the keyboard buffer. When scanf(" d" &n); is used and when an input is entered the newline character("n") along with the input is stored in buffer. This buffer gets clear as the user presses "Enter" or if the buffer is full.

So when we use the scanf(" d" &n); the "n" is left in the buffer itself. So the buffer will fill the string with " ". Hence it will not print anything in place of string.

The Following code will help in understanding this point.

#include<stdio.h>
int main()
{
int n;
char string[20];

printf("String :: s" string);

printf("Enter the number");
scanf(" d" &n);

printf("nEnter the string");
gets(string);

printf("Number :: d" n);
printf("String :: s" string);
if(strcmp(string " ") 0)
printf("Null string");
system("pause");
return 0;
}

Here initially i am trying to print the contents of the string.... It gives garbage.Later
in the output Null string will be displayed. Which means the string is containing " ".

Note :
When we change the order ie. gets(string); and then scanf( d" &n); we will not have this problem.

Solution :
The solution for such problems is to use fflush(stdin); This clears the keyboard buffer. Hence we can get the desired output. This fflush() should be used after entering the input. ie after scanf() and before gets().

#include<stdio.h>
int main()
{
int n;
char string[20];

printf("String :: s" string);
printf("Enter the number");
scanf(" d" &n);
fflush(stdin);
printf("nEnter the string");
gets(string);

printf("Number :: d" n);
printf("String :: s" string);
if(strcmp(string " ") 0)
printf("Null string");
system("pause");
return 0;
}

Hope i answered correctly. If you have any doubt feel free to ask it.

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