doubt in graphics

[rampraveen]

#include "stdio.h"
#include "conio.h"
#include "graphics.h"
char far *vidmem=0xB8000000;
main()
{
 
    int gm,gd=DETECT;
    int r,c,i;
    char message[]="praveen";
    initgraph(&gd,&gm,"");
 
    clrscr();
    for(r=5;r<=20;r++)
    {
        for(c=5;c<=50;c++)
            write2vdu('',64,r,c);
    }
    c=10;
    for(i=0;i<=10;i++)
    {
        write2vdu(message[i],77,10,c);
        c++;
    }
    getch();
}
write2vdu(char ch,char attr,int row,int col)
{
char far *v;
v=vidmem+row*160+col*2;
*v=ch;
v++;
*v=attr;
}  

when i run this, it just show only white screen..but the author of this program says tat will show a box with some texts..any one help me to get correct output.thankyou....

[weaknessforcats]

I don't have a compiler old enough to compile thbs code.

I havent't seen far pointers in 20 years. Where did this code come from?

[rampraveen]

@weaknessforcats
from one c graphics book..

[rampraveen]

am using xp and intel motherboard..any problems wit tat..

[weaknessforcats]

I am not able to compile this code so I can't analyse it for you. Sorry.

[rampraveen]

@weaknessforcats
it's k..i have one doubt in tat program..tat means in that top of the prgm we are using "char far *vidmem=0XB8000000;"
will u tell why we are using this..?,...thk u...

[weaknessforcats]

vidmem is used in a calculation. The 0XB8000000 must have somethibng to do with the amount of video memory.

The fact that vidmen is a char far* means the pointer is located outside the current code segment. For this to work you need a compiler old enough to use segmented memory models which went out of existence about 1990.

Basically, I don't believe the code is going to work using any modern computer/compiler/video driver.

[drhowarddrfine]

@weaknessforcats
gcc will. I'm pretty sure that video address is still used though I don't know how Windows would react to it. I still see assembly code passed around using that on the assembly forums I visit. I haven't paid attention to this stuff in a few years though.

[newb16]

In real mode (including emulation of it in dos box in windows), 0xB800:0000 is the starting address of display buffer of cga (ega, vga) adapter in text mode. The problem is that write2vdu expects the text mode to be on, but initgraph puts the adapter into graphics mode.

[rampraveen]

thanks friends at last i got a correct output with windows xp also........thk you for all.......