A. Introduction: why do computers use binary numbers?

Numbers have to be saved in computers so they can be used or calculated. The storage unit are electronic circuits. We have to use different "statuses" of the circuits to represent numbers. Since 2 different statuses are much easier to identify than 10 statuses, all computers use binary system for number storage and operations.

B. Watch (__slides__)

C. Try: how are arithmetic operations done in binary system?

11101 + 01010 = ? ; 1010101 + 1101010 = ? ;

11101 - 01010 = ? ; 1010101 - 1101010 = ? ;

11101 * 01010 = ? ; 1010101 * 1101010 = ? ;

11101 / 01010 = ? ; 1010101 / 1101010 = ? .

100111; 10111111

10011; -10101

100100010; 10001100110010

10; 1

100111;

10111111 ;

10011;

-101011

100100010 ;

10001100110010 ;

10;

0;

1) 100111

2) 10011

3) 100100010

4) 0011

5)10111111

6)-0010101

7)10001000110010

8)0000000