Thread: getchar() and putchar(c)

Hello everyone, this is my first post.

I also, began to learn programming only a week ago.

This is an example in Kernighan and Ritchie book ("The C programming language).

Code:

#include <stdio.h>

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

My question is: Why putchar print all the characters taken by getchar and not only the last one ?

Notice that the putchar call is within the loop body, i.e., we could also have written:

Code:

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

EDIT:
By the way, good job with the code bbcode tags and proper indentation. Note though that in modern C, main should be declared as explicitly returning an int and with void as the parameter, unless you want command line arguments, e.g.,

Code:

int main() {

You should also explicitly return 0; at the end of main unless compiling with respect to C99 or later.

Originally Posted by laserlight

Notice that the putchar call is within the loop body, i.e., we could also have written:

Code:

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

EDIT:
By the way, good job with the code bbcode tags and proper indentation. Note though that in modern C, main should be declared as explicitly returning an int and with void as the parameter, unless you want command line arguments, e.g.,

Code:

int main() {

You should also explicitly return 0; at the end of main unless compiling with respect to C99 or later.

You are right, the book is old and it's normal that its content may be deprecated.

I still don't know what is the meaning of void (because i haven't studied it yet).

But my question is: why putchar insert the output only when I press Enter, and all the characters, not the last only ?

Originally Posted by an96

why putchar insert the output only when I press Enter, and all the characters, not the last only ?

That has to do with how input to the console is handled by the system. Most of the time it's line-buffered, meaning it waits for the user to input a whole line before passing it to the program.

Originally Posted by an96

I still don't know what is the meaning of void (because i haven't studied it yet).

In this context it means that you declare that the main function does not take any arguments.

Originally Posted by an96

But my question is: why putchar insert the output only when I press Enter, and all the characters, not the last only ?

When you press enter, the input enters the standard input buffer (or rather the standard input stream, as that is the concept in C), upon which getchar reads the first character (as an unsigned char converted to int), prints it, then reads the second character, prints it, etc, until getchar returns EOF (i.e., it has detected end of file or an input error).