Turbo - C

[Scott M Glen CS89]

Can anyone tell my why the following Turbo-c code causes a crash. (I am using
Turbo-c V2, on an NTS PC).

Basically it's a trivial piece of code, to save a small rectangular area of
the screen to memory, write something in the area (in this case a black
rectangle) and then restore the screen to its original status. 



void
help_option1 (void)

{
int i;
void *buffer;
unsigned size;

size=imagesize(0,0,20,20);  /* define rectangle to be saved */
if (size!=-1)               /* if area is too large imagesize returns -1 */
   {
   buffer=malloc (size);    /* allocate memory for area of screen */
   getimage (0,0,20,20);
   
   setfillstyle (SOLID_FILL,BLACK);
   bar (0,0,20,20);         /* black out the rectangle */
   i=getch();               /* wait for a key */

   putimage (0,0,buffer,COPY_PUT);   /* restore rectangle 
   free (buffer);
   }
else
   {
   /* image too large */
   }
}

When it runs, the black box apewars as expected, but then the screen freezes
I don't even know whether the problem lies with saving the area, or restoring 
it.

Any help would be very much appreciated.....


******************************************************************************
*				                                             *	
*  Scott Glen                                                                *
*  3rd Year Computer Science                                                 *
*  The University Of Strathclyde                                             * 
*  Glasgow                                                                   *
*  Scotland                                                                  *
*                                                                            *	
*  cadx830 at uk.ac.strathclyde.computer-centre-sun			     *
*          sglen at uk.ac.strathclyde.cs				             *	
*                                                   		             * 
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