Graphics video memory in c using far pointer



(b)Graphics video memory:

Segment number 0XA is known as graphics video memory. This segment has 720 columns and 400 rows.
Intersection of rows and columns is known as pixel. Size of each pixel is one byte which stores color information.


Example:

(q)What will be output of following c program?

#include <dos.h>
#include<stdio.h>

int main(){

int j;
union REGS i,o;
char far *ptr=(char *)0XA0000000;

i.h.ah=0;
i.h.al=0x13;
int86(0x10,&i,&o);

for(j=1;j<=100;j++){
*(ptr+j)=4;
}

return 0;
}

Output: One red color line in the graphics console as shown in the following figure






In the above program what is following codes?
union REGS i,o;
i.h.ah=0;
i.h.al=0x13;
int86(0x10,&i,&o);

Answer:

The task of this code is to switch the 256 bit color graphics console window from default console window of Turbo c++ IDE.

More examples:

Copy the following code and execute the code in Turbo c compile and see what is displaying.

(1)What will be output of following c program?

#include <dos.h>
#include<stdio.h>

int main(){

int j,k;
union REGS i,o;
char far *ptr=(char *)0XA0000000;

i.h.ah=0;
i.h.al=0x13;
int86(0x10,&i,&o);

for(k=0;k<100;k++){
for(j=1;j<=319;j++){
*(ptr+j+k*320)=k;
}
}

return 0;
}


(2)What will be output of following c program?

#include <dos.h>
#include<stdio.h>

int main(){

int j,k;
union REGS i,o;
char far *ptr=(char *)0XA0000000;

i.h.ah=0;
i.h.al=0x13;
int86(0x10,&i,&o);

for(k=0;k<100;k++){
for(j=1;j<=319;j++){
*(ptr+j+k*320)=k;
}
}

return 0;
}







Generic pointer

Null pointer
Wild pointer
Dangling pointer
Near pointer
Far pointer
Graphics video memory
Text video memory
Huge pointer
Memory model in C
C tutorial

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