Thread: What does getchar do with the second next character from stdin?

What does getchar do with the second next character from stdin?
Example :

example = getchar();

User input :

ABC

Output :

A

Where does the BC goes?

Originally Posted by xeon321

What does getchar do with the second next character from stdin?
Example :

example = getchar();

User input :

ABC

Output :

A

Where does the BC goes?

BC are maintained into the buffer.Try this code in oder to understand how this works.

Code:

 char a;
    printf("Please type a word\n");
    while(1)
    {
        a=getchar();
        printf("%c\n",a);
    }

Stdin is line buffered, if you type ABC and hit enter getchar() will get 1 char from the buffer, the first one happens to be A.

Code:

while( (example = getchar()) ) {
     putchar(example);
}

Originally Posted by std10093

BC are maintained into the buffer.Try this code in oder to understand how this works.

Code:

 char a;
    printf("Please type a word\n");
    while(1)
    {
        a=getchar();
        printf("%c\n",a);
    }

Hmm interesting example.
Mind to explain why you use while(1) ? What does the 1 do?

Originally Posted by xeon321

For this one, it will work if the user's input is YYYYYYYYYYYYYYYYYYYYY. As long as the first character is Y.
How to make it display "Oops! Wrong entry!" message?

Code:

#include <stdio.h>

int main() {

char example;

printf("Enter Y : ");
example = getchar();

while ( example != 'Y' && example != 'y')
{
 printf("Oops! Wrong entry!");
 example=getchar();
}

printf("Not looped");

return 0;
}

If you type "sam" for instance,"Oops! Wrong entry!" will be displayed.I have not understand what is your goal though

Originally Posted by std10093

If you type "sam" for instance,"Oops! Wrong entry!" will be displayed.I have not understand what is your goal though

Yes, sam. It will display the error, of course. Because the first character is 's'.

My point is, I entered ' YYYYYYYYYYYYYYYYYYYYYYYYYY ' , yes the first character is Y. But from what I see, I am not entering the character 'Y' only, but a string "YYYYYYYYYYYYYYYYYYYYYYYYYYY".
How do I fix that problem?

Originally Posted by xeon321

Hmm interesting example.
Mind to explain why you use while(1) ? What does the 1 do?

In order the loop is infinite.Any nuber different that zero gives as a true statement,so the condition of while is satisfied,so our programm is going to enter the loop infinite times.

For example

Code:

int a=5;
if(a==5)
{
   printf("entered the loop\n");
}

is equivalent to (the message will be dispalyed
For example

Code:

if(1)
{
    printf("entered the loop\n");
}

Originally Posted by std10093

In order the loop is infinite.Any nuber different that zero gives as a true statement,so the condition of while is satisfied,so our programm is going to enter the loop infinite times.

For example

Code:

int a=5;
if(a==5)
{
   printf("entered the loop\n");
}

Mmm, and from where the computer knows the number is different than zero?

Originally Posted by xeon321

Hmm, define what is correct input & wrong input?

while( example != 'Y'&& example != 'y')

I thought this line means , except 'Y' & 'y', the rest of the characters are not accepted?

The code that you wrote is going to check only the first letter of the word.If the 1st letter is different than Y or y ,then user inputs another(or the same word).Your code is going to ckeck again only the first letter of the word.

Originally Posted by xeon321

Mmm, and from where the computer knows the number is different than zero?

a is equal to 5
so a==5 is a true statement.True statements are equivalent as 1(boolean algebra) and false statements as 0.
a==6 is a false statement,it is equivalent to zero

Originally Posted by laserlight

Yes, but "the rest" refers to the range of characters that are not accepted. It has nothing to do with the characters that you have yet to read. If you want to discard them, then you need to read and ignore them until you read a new line (i.e., use a loop).


a==5 evaluates to 1, and 1 is obviously not 0.

So I can't really prevent the user from inputting ridiculous answer and give him an error message?

Users are free to input anything(most times by mistake they give false inputs ) .Of course you can,by writing suitable code!