C中的回车？

Question

Output of Following program is : hai

I didn't get how the \\r carriage return works in this program and in real can any one help me out ?

#include <stdio.h>
#include<conio.h>

void main()
{
    printf("\nab");
    printf("\bsi");
    printf("\rha");
    _getch();
}

Answer 1

From 5.2.2/2 (character display semantics) :

\\b ( backspace ) Moves the active position to the previous position on the current line. If the active position is at the initial position of a line, the behavior of the display device is unspecified.

\\n ( new line ) Moves the active position to the initial position of the next line.

\\r ( carriage return ) Moves the active position to the initial position of the current line.

Here, your code produces :

• <new_line>ab
• \\b : back one character
• write si : overrides the b with s (producing asi on the second line)
• \\r : back at the beginning of the current line
• write ha : overrides the first two characters (producing hai on the second line)

In the end, the output is :

\nhai

Answer 2

Program prints ab , goes back one character and prints si overwriting the b resulting asi . Carriage return returns the caret to the first column of the current line. That means the ha will be printed over as and the result is hai

Answer 3

Step-by-step:

[newline]ab

ab

[backspace]si

asi

[carriage-return]ha

hai

Carriage return, does not cause a newline. Under some circumstances a single CR or LF may be translated to a CR-LF pair. This is console and/or stream dependent.