2. Hardware Basics: Inside the Box 2

3.  2001 Prentice Hall2.2 Chapter Outline “There is no invention – only discovery.” Thomas J. Watson, Sr. What Computers Do A Bit About Bits The Computer’s Core: CPU and Memory

4.  2001 Prentice Hall2.3 What Computers Do Receive input Process Information Produce Output

5.  2001 Prentice Hall2.4 What Computer Do Store Information

6.  2001 Prentice Hall2.5 Input Devices Computers accept information from the outside world The keyboard is the most common input device Pointing devices like the mouse also receive input

7.  2001 Prentice Hall2.6 Output Devices Computers produce information and send it to the outside world. A video monitor is a common output device. Printers also produce output.

8.  2001 Prentice Hall2.7 Process Information The processor, or central processing unit (CPU), processes information and performs all the necessary arithmetic calculations. The CPU is like the “brain” of the computer.

9.  2001 Prentice Hall2.8 Store Information Memory and storage devices are used to store information Primary storage is the computer’s main memory Secondary storage uses disks or other media

10. Input devices Output devices Processors Storage Hardware

11.  2001 Prentice Hall2.10 Information Information comes in many forms Words... Numbers... Pictures... Sounds Computers only understand information in digital form  Information must be broken into bits

12.  2001 Prentice Hall2.11 A Bit About Bits A bit (binary digit) –is the smallest unit of information –can have two values –can represent numbers, codes, or instructions Think of these values as switches: yes and no, black and white, high and low, or on and off “ Even the most sophisticated ocmputer is really only a large well- organized volume of bits.” David Harel

13.  2001 Prentice Hall2.12 More about Bits Each switch can be used to store a tiny amount of information, such as: –An answer to a yes/no question –A signal to turn on a light Larger chunks of information are stored by grouping bits as units –8 bits (byte) = 256 different messages

14.  2001 Prentice Hall2.13 Bits as Codes ASCII - American Standard Code for Information Interchange –most widely used code, represents each character as a unique 8-bit code.

15.  2001 Prentice Hall2.14 Bits as Instructions The computer stores programs as collections of bits. –For instance, 01101010 might instruct the computer to add two numbers. Other bit instructions might include where to find numbers stored in memory or where to store them.

16.  2001 Prentice Hall2.15 Bits, Bytes, and Buzzwords Common terms might describe file size or memory size: –Bit: smallest unit of information –Byte: a grouping of eight bits of information –K: (kilobyte); about 1,000 bytes of information - technically 1024 bytes equals 1K of storage.

17.  2001 Prentice Hall2.16 Bits, Bytes, and Buzzwords MB: (megabyte): about 1 million bytes of information GB: (gigabyte): about 1 billion bytes of information TB: (terabyte): about 1 million megabytes of information

18.  2001 Prentice Hall2.17 The Computer’s Core: The CPU and Memory The transformations are performed by the CPU - the central processing unit or processor. The microprocessor, which is a silicon chip, is located on the motherboard.

19.  2001 Prentice Hall2.18 The CPU: The Real Computer When purchasing a computer, selecting a CPU is very important. The two most critical factors are compatibility and speed.

20.  2001 Prentice Hall2.19 Compatibility Not all software is compatible with any given CPU. Each computer has a unique instruction set - a vocabulary of instructions the processor can execute. New microprocessors can usually run older software, but new software is not usually compatible with old microprocessors.

21.  2001 Prentice Hall2.20 Speed The computer’s speed is measured by the speed of its internal clock - a device to synchronize the electric pulses. Speed is measured in units called megahertz (mHz).

22.  2001 Prentice Hall2.21 Speed A computer’s speed cannot be judged by megahertz alone. Speed is also determined by the architecture of the processor – how individual components of the CPU are put together on the chip.  Newer chips can manipulate more bits simultaneously than older chips.  Typically a CPU can process between 16 to 64 bits.

23.  2001 Prentice Hall2.22 Speed Manufacturers have switched from CISC to RISC processors so tasks can be performed faster. CISC - complex instruction set computer RISC - reduced instruction set computer

24.  2001 Prentice Hall2.23 Speed Parallel processing places multiple processors in a computer. Most supercomputers have multiple processors that divide jobs into pieces and work in parallel on the pieces.

25.  2001 Prentice Hall2.24 The Computer’s Memory RAM (random access memory): –is the most common type of primary storage, or computer memory –is used to store program instructions and data temporarily –unique addresses and can be stored in any location –can quickly retrieve information –will not remain if power goes off (volatile)

26.  2001 Prentice Hall2.25 The Computer’s Memory ROM (read-only memory): –information is stored permanently on a chip. –contains startup instructions and other permanent data.

27.  2001 Prentice Hall2.26 Buses, Ports, and Peripherals Information travels between components through groups of wires called buses. Buses connect to storage devices in open areas in the box called bays.

28.  2001 Prentice Hall2.27 Buses, Ports, and Peripherals Busses also connect to slots inside the computer as well as sockets on the outside of the computer called ports.

29.  2001 Prentice Hall2.28 Buses, Ports, and Peripherals Slots and ports also allow external devices called peripherals to be added to the system (keyboard, monitor, and mouse). Without peripherals, the CPU and memory are like a brain without a body.