clrscr(); and getch(); requires the header file conio.h i.e #include <conio.h>

clrscr();  :- This is use to clear the output screen i.e console

suppose you run a program and then alter it and run it again you may find that the previous output is still stucked there itself, at this time clrscr(); would clean the previous screen.

One more thing to remember always use clrscr(); after the declaration like

int a,b,c;

float total;

clrscr();

getch(); :- getch is used to hold the screen in simple language, if u dont write this the screen

will just flash and go away....