Mouse can be used in text mode as well as in graphics mode. Usually it is used in graphics mode. Hence we must first change over to graphics mode. In our program the function initgraph() is responsible for switching the mode from text to graphics .DETECT is a macro defined in ‘graphics.h’. It requests initgraph() to automatically determine which graphics driver to load in order to switch to the highest resolution graphics mode. The initgraph() function takes three parameters, the graphics driver, the graphics mode and the path to the driver file.
Once the driver has been loaded, initgraph() sets up the numeric values of the graphics mode chosen in the variables gd and gm respectively. Here we are assuming that the driver files are in the directory ‘c:\tc\bgi’. Hence the path passed to initgraph() is ‘c:\tc\bgi’.
The various mouse functions can be accessed by setting up the AX register with different values (service number) and issuing interrupt number 51. The functions are listed below.
| Interrupt | Service | Purpose |
| 51 | 0 |
Reset mouse and get status
Call with AX = 0 Returns: AX = FFFFh If mouse support is available Ax = 0 If mouse support is not available |
| 51 | 1 |
Show mouse pointer
Call with AX = 1 Returns: Nothing |
| 51 | 2 |
Hide mouse pointer
Call with AX = 2 Returns: Nothing |
| 51 | 3 |
Get mouse position and button status
Call with AX = 3 Returns: BX = mouse button status Bit Significance 0 button not pressed 1 left button is pressed 2 right button is pressed 3 center button is pressed CX = x coordinate DX = y coordinate |
| 51 | 4 |
Set mouse pointer position
Call with AX = 4 CX = x coordinate DX = y coordinate Returns: Nothing |
| 51 | 7 |
Set horizontal limits for pointer
Call with AX = 7 CX = minimum x coordinate DX = maximum x coordinate Returns: Nothing |
| 51 | 8 |
Set vertical limits for pointer
Call with AX = 8 CX = minimum y coordinate DX = maximum y coordinate Returns: Nothing |
Let us consider a program which makes use of the above functions.
A SIMPLE PROGRAM TO CALL MOUSE POINTER
#include < graphics.h >
#include < stdio.h >
#include < conio.h >
#include < dos.h >
union REGS in,out;
void callmouse()
{
in.x.ax=1;
int86(51,&in,&out);
}
//MAIN FUNCTION
void main()
{
int x,y,cl,a,b;
clrscr();
int g=DETECT,m;
initgraph(&g,&m,”");
callmouse(); // CALLING MOUSE FUNCTION
getch();
}
callmouse() :- In this function AX is set to “1″. When this function is called in main() it displays the mouse pointer. The position of the pointer can be changed by using the mouse.
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