closegraph function closes the graphics mode, deallocates all memory allocated by graphics system and restores the screen to the mode it was in before you called initgraph.
Declaration: void closegraph();
C code of closegraph
#include<conio.h>
main()
{
int gd = DETECT, gm;
initgraph(&gd, &gm, "C:\\TC\\BGI");
outtext("Press any key to close the graphics mode...");
getch();
closegraph();
return 0;
}