Thread: clearing the screen

Is there a way to clear screen after a while loop has taken place, so it starts program again but not at the bottom of the last text?

Brad.

You can use clrscr() like hermit suggested but I think this command is not supported on all systems. If it's not supported on your system you can always use the system command:

Code:

system("cls");

Originally posted by Hammer

And cls is supported on all systems is it? [/sarcasm]

You're not listening... I said you could always use the system command.

Originally posted by Hammer


... and the example you gave was specifically using cls, with no mention that that was OS dependant. A newbie might not spot that and could get confused when it didn't work.

And yes I was listening

A newbie should always read the manual pages. In the manual pages you can read how the function works...

But since manual pages are like FAQ pages (nobody reads it), you are probably right. I should have told that the cls command is an operating system command and can be different on any OS.

Option 1

#include <conio.h>
... code ...
clrscr();
... more code...

advantages:
clears the screen...

disadvantages:
... but only on MS-DOS systems with compilers that support it in this manner.
Who says there is a screen connected to standard output anyway?

Errors in FAQ:
nothing significant, except for not mentioning there might not be a screen.

Option 2

putcharing newlines and scrolling over

Advantages:
none

disadvantages:
there may not be a scree - printing 50 lines to the printer doesn't clear the screen
printing 50 lines to a 63 line screen also doesn't clear the screen

Errors in FAQ:
"It works" is wrong. It clearly doesn't work quite so widely as is implied by this phrase.

Option 3

Using a library to do it for you

Advantages:
You don't have to think about whether it works or not
Possibility of slightly portable code, but not universally portable code.

Disadvantages:
Getting a library to do the job
Getting a library which doesn't fall into the 'clearing the screen' errors
Who says there is a screen anyway?

Errors in FAQ:
Nothing significant for this bit, except for the possibility that there might not be a screen attached to stdout.

Option 4

Write directly to video memory

Advantages:
None

Disadvantages:
Highly platform dependent
Who says the program is outputting to that display device, to that framebuffer or even outputting anything to the screen at all?

Errors in FAQ:
Again, this certainly doesn't 'work' since it's completely non portable and depends heavily on the machine running it.

Option 5

Using curses on unix systems

Advantages
It works....

Disadvantages
... but only on unix systems which have curses.

Errors in FAQ:
None, but this is really a special case of option 3

My prefered answer is simply:
There is no way of doing it in C. No matter what you will need to use platform specific techniques. Find the techniques for your platform and use them, being aware that moving your code to other platforms (or even future or past versions of the same platform) might mean your code doesn't work.

Ian Woods

Option 4

Write directly to video memory

Advantages:
None

Disadvantages:
Highly platform dependent
Who says the program is outputting to that display device, to that framebuffer or even outputting anything to the screen at all?

This should work w/o problems w/ the following conditions...
1. Platform is DOS.
2. Screen Resolution (text mode) 25×80 (25 rows by 80 cols)

#include<stdio.h>
main()
{
char far *vm= (char far *) 0xB8000000;
int i;
for(i=3998;i>=0;i-=2)
*(vm+i)=32; /* space character */
}

With little modifications u can run it for other text modes also.

-Harsha