1. Bits & Bytes Why computers use binary

2. Analog Signals Analog signals : constantly changing values – Difficult to make precise

3. Digital Digital signals : only allowed to have specific values

4. Binary Computers are digital systems with 2 possible states: on or off – Called a binary system

5. Analog Signals Analog values converted to binary with a threshold value

6. Analog Implementation of Binary Even if actual values are somewhat noisy Correct binary value is preserved

7. Why Binary 1.Unambiguous signals (easy to tell 1 from 0) – Storing, copying data can be done without errors 2.Simple, easy to build – 1/0 easier to build than 1/2/3/4/5/6/7/8/9/0 3.Anything that can be represented with some sort of pattern can be represented with patterns of bits

8. Bits Bit : single on/off value Represented as: – A mechanical electrical switch. – Voltage on a wire. – Magnetic field of a small slice of metal. – A hole punched in a card. – A tiny part of the light-reflecting surface of a CD. …

9. Bit Patterns One bit : 2 possible values: 0 1

10. Bit Patterns One bit : 2 possible values: 0 1 Two bits : 4 possible values 00 01 10 11

11. Bit Patterns Two bits : 4 possible values 00 01 10 11 Three bits : 8 possible values 000100 001101 010110 011111

12. Bit Patterns Four bits: 16 values Five bits: 32 values … n bits: 2 n values

13. Bytes 1 bit (1/0) usually not useful on its own Usually work in larger chunks – Byte : 8 bits – Special names for large collections of bytes: NameNumber of Bytespower of 2 byte12020 kilobyte (KB)10242 10 megabyte (MB)1,048,5762 20 gigabyte (GB)1,073,741,8242 30 terabyte (TB)1,099,511,627,7762 40