Thread: FYI - a simple way to clear the screen

okay i always found clrscrn() or whatever it is confusing, and didnt wanna do it everytime i wanted to clear the screen...thanks to the people that helped me in the "running bat files in C " thread...i found an easier way. sorry if you think it was stupid to post this...and that it is only clutter. but i found it useful anyways heres how: (and sorry if most if you knew about this before)

Code:

#include <stdio.h>
#include <system.h>

main()
{
	printf("Now you see me..[press any key]");
	getche();
	
                system("cls");

	printf("..now you don't.");

	getche();
}

i use the getche at the end because on windows xp it terminates the program automaticaly if hteres no more code...arghhh i hate that.

so you could use a function with this and call it when ever you need.

>system("cls");
This would work...but only on certain platforms and it would slow down the program considerably because the overhead for the system function is obscene.

-Prelude

Prelude,

Overhead.

A concept that I inherently accept - like many others, I would presume - but, what, exactly, are we talking about?

Conceptually, (where's my thesuarus), I understand that "overhead", at the low-level, brings much into the execution of the program, often inadvertently.

What exactly is it?

Where can we look for it?

How do we avoid it?

(It's a lot of pressure to be put under, but you're young, and I'm...not quite so young. )

-Skipper

this one works with every compiler

Code:

void my_cls()
{
    int i;
    for( i=0; i<=25; i++)
    { printf("\n"); }
}

then use my_cls(); to clear the screen by printing 25 new lines

Originally posted by dune911
this one works with every compiler

Code:

void my_cls()
{
    int i;
    for( i=0; i<=25; i++)
    { printf("\n"); }
}

then use my_cls(); to clear the screen by printing 25 new lines

I'm bored so I'm going to be really picky That's 26 newlines, not 25.

What exactly is it?

overhead

1. Resources (in computing usually processing time or storage space) consumed for purposes which are incidental to, but necessary to, the main one. Overheads are usually quantifiable "costs" of some kind.

In this case the cost of calling system is speed. The system function has to request an operation from environment by sending it an implementation-defined string. As you can probably imagine, this takes quite a bit of time. On my system I called system ( "cls" ); one time and it increased the running time of my program by over 200 milliseconds. Imagine what happens if you tried to clear the screen regularly?

>Where can we look for it?
Overhead can be any kind of resource that your program uses, just look for any point where you might use a great deal of it.

>How do we avoid it?
Careful design.

>this one works with every compiler
Perhaps every compiler, but it may not always work as well as you want it to. What if the size of the console screen is larger than 25 rows? What if there isn't even a screen? A lot of C programs run on platforms where there is no screen output, everything goes to a file, I personally wouldn't want to read a file with 26 newlines in between every bit of real data.

In the end, there's no standard, portable, effective, efficient way to clear the screen usefully. And in most cases one can do without clearing the screen since those users who would care about it will rarely use a command line program and much of the time those who use command line programs regularly will redirect the output to a file.

-Prelude

@Hammer
whoops you're right... i=0 not i=1...

@Barjor
can you tell me how, please?

I think I would use gotoxy(1,1);

edit se below....Never needed gotoxy() myself so maybee I should just keep my hands away from the keyboard.

Also taken from the faq if you are using console

Code:

#include <windows.h>
void gotoxy(int x, int y)
{
   COORD coord;
   coord.X = x;
   coord.Y = y;
   SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), coord);
}

yes, i am using the console (but never included windows.h, yet)
thanks Barjor

Prelude,

Thanks for the assist on the "overhead" issue. Undoubtedly the most definitive information I've run across on the topic.



-Skipper