C Programming (Beginner help) relating to getchar() putchar()

Question

Im new to C programming and wanted to clear, what may seem to be, a silly doubt...

Code:

#define EOF 0
main()
{ 
    int c;

    c=getchar();
    while (c!= EOF) 
    {
        putchar (c); 
        c= getchar();
    }
}

this should just return the value I enter...but accordingly...shouldnt it terminate when I enter 0? If not...what exactly does the statement under 'while' signify? Any help would be greatly appreciated guys :)

When you enter '0', it reads the ASCII character '0', not the numeric value. — tafa, May 23 '12 at 06:51

score 2 · Answer 1 · answered May 23 '12 at 06:47

2

EOF means when you hit, for instance, ctrl + d in linux, it sends EOF signal, it's not necessarily a 0.

answered May 23 '12 at 06:47

Andreas Wong

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score 1 · Accepted Answer · answered May 23 '12 at 06:52

The getchar function returns the ASCII value entered (48 for zero, or '0'), or a value called EOF in the header file <stdio.h> (normally -1).

So if you want to stop either on EOF (the proper EOF, not the one you defined) or if the user writes a zero, then this will work much better:

#include <stdio.h>

int main()
{
    int c = getchar();

    while (c != EOF && c != '0')
    {
        putchar(c);
        c = getchar();
    }

    return 0;
}

Thanku, i was gettin mixed up in the basics :) – Aki May 24 '12 at 07:01 — Aki, May 24 '12 at 07:01

Dave · Answer 3 · 2012-05-23T06:58:16.187

EOFis certainly not 0 (nor is it '0', the char literal equaling 48). It's not char at all. stdio.h (which you should be #include-ing!) defines it as -1. It indicates that whatever file you are reading has no more data in it. It's not a byte in the stream, rather the way that the io library indicates that it has finished.

The whole reason getchar needs to return an int is so that the end-of-file indicator cannot possibly be a valid byte in the file.

Other functions indicate that the EOF has been reached differently: fgets() returns NULL. read() which returns the number of bytes read returns 0, indicating that it could read nothing.

Thank you, but i guess with what i wanted...i shud have put as #define '0' instead of just 0 :) — Aki, May 24 '12 at 07:03

score 0 · Answer 4 · answered May 23 '12 at 06:52

0

When you enter a 0, it's not actually a zero, just the ASCII character 0. It has a numerical value of 48, which can be verified by printf("%d\n", '0');, which prints 48. An EOF is an actual zero, that is, it's representation is essentially zero.

answered May 23 '12 at 06:52

Sufian Latif

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C Programming (Beginner help) relating to getchar() putchar()

4 Answers4