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Home » Tip Bank » C++
Language: C++
Expertise: Beginner
Mar 13, 1998

System calls for Clearing Screen

Question:
Right now i'm still learning Visual C++, version 4.0. It may seem like the easiest thing in batch or Basic languages, but I can't figure out how to clear the screen in C++. The program I'm working on is DOS based. Also, can you help me with System Calls? (like running an external program from a program)? thnx alot, I appreciate your help.

Answer:
The very thing that gives C its portability is the fact that it is not tied to any hardware. Although the flexibility is certainly there, it is certainly harder to clear the screen, for example, than it is in a language such as Basic.

Depending on your compiler, you could use syntax similar to the following. This cls() function uses int86 to call the ROM-BIOS services and clear the screen.

#include 

void cls()
{
   union REGS regs;

   regs.h.ah = 0x06   // ROM-BIOS scroll service
   regs.h.al = 0      // Number of lines to scroll (0 clears)
   regs.h.bh = 0x07   // Color of cleared area
   regs.h.ch = 0      // Top row of area to clear
   regs.h.dh = 24     // Bottom row of area to clear
   regs.h.cl = 0      // Left column of area to clear
   regs.h.dl = 79     // Right column of area to clear
   int86(0x10,®s,®s); // Call ROM BIOS
}
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