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 1001011

100110010 10010010010010

1) 100111

2) 10011

3) 100100010

4) 0011

5)10111111

6)-0010101

7)10001000110010

8)0000000

100111;

10111111 ;

10011;

-101011

100100010 ;

10001100110010 ;

10;

0;

100111; 10111111

10011; -10101

100100010; 10001100110010

10; 1