Chapter Two Hardware Basics Inside the Box Chapter

Chapter Two Hardware Basics: Inside the Box

Chapter Outline • What Computers Do • A Bit About Bits • The Computer’s

What Computers Do Four basic functions of computers include: – – Receive input Process

Input Devices Computers accept information from the outside world. The keyboard is the most

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. © 1999 Addison Wesley Longman 5

Output Devices Computers produce information and send it to the outside world. A video

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. Primary storage © 1999 Addison Wesley Longman Secondary storage 7

A Bit About Bits A bit (binary digit) – is the smallest unit of information – can have two values - 1 and 0. Binary digits, or bits, can represent numbers, codes, or instructions. © 1999 Addison Wesley Longman On Off 8

Bits as Numbers Binary number system - a system that denotes all numbers and combinations of two digits. The binary system uses two digits to represent the numbers 0 and 1. © 1999 Addison Wesley Longman 9

Number System (I) • decimal system ( base 10 ) • octal system (

Number System (II) • decimal octal binary 0 1 2 3 4 5 6

To Represent Negative Numbers • • biased sign magnitude 1’s complement 2’s complement ©

Biased Numbers • decimal 0 000 1 001 2 010 3 011 4 100

Sign Magnitude Numbers • sign -3 -2 -1 -0 0 1 2 3 ©

1‘s Complement Numbers • -3 -2 -1 -0 0 1 2 3 100 101

2‘s Complement Numbers • -4 -3 -2 -1 0 1 2 3 100 101

1‘s Complement Addition • BCD addition • carry end around • result always correct when two operands have different sign • overflow when two positive operands add to a negative result • underflow when two negative operands add to a positive result © 1999 Addison Wesley Longman 17

2‘s complement Addition • BCD addition • carry dropped • result always correct when two operands have different sign • overflow when two positive operands add to a negative result • underflow when two negative operands add to a positive result © 1999 Addison Wesley Longman 18

Floating Point Representation • = 12345 * 10 -2 = 1234. 5 * 10 -1 = 123. 45 = 12. 345 * 101 = 1. 2345 * 102 = 0. 12345 * 103 — normalized form = 0. 012345 * 104 … • 21. 75 = 10101. 11 = 0. 1010111 * 25 © 1999 Addison Wesley Longman 19

PDP-11, VAX-11 Floating Point Representation sign mantissa 0 100001011100……. 0 8 bits 23 bits

IBM 360/370 Floating Point Representation • 21. 75 = 10101. 11 B = 15. CH =. 15 C * 162 0 1000010 0001 0101 1100 0000 4 2 1 5 C 0 0 0 • precision 1/221 ~ 1/106 • range 1663 = 2252 ~ 1078 © 1999 Addison Wesley Longman 21

Bits as Codes ASCII - American Standard Code for Information Interchange - most widely

Code & Character Sets • ASCII ( American Standard Code for Information Interchange ) — 7 bit 0 1 2 8 9 A 0| 1| 2| ! ` ( ) / 3| 0 1 7 8 9 4| @A B © 1999 Addison Wesley Longman H I J 3 B 4 C 5 D 6 E 7 F “ * # + $ - % , &. 2 3 4 5 6 C K D L E M F N G 23 O

Code & Character Sets (IV) • EBCDIC ( extended BCD for information exchange code ) — 8 bit 0 8 6 7 E F 8 | f g h 9 | o p q A | w x y © 1999 Addison Wesley Longman B | 1 9 2 A 3 B 4 C 5 D a i j r b c d e k l m n s t u v z 24

Chinese Characters • Big-5 2 byte ( 16 bit ) 13461字 • CNS 11643

File & Record • files – program file – data file • Record –

Type of Data • numerical – integer, real, double precision, complex, … • non-numerical

Bits as Instructions The computer stores programs as collections of bits. For instance, 01101010 might instruct the computer to add two numbers. (OP code) Other bit instructions might include where to find numbers stored in memory or where to store them. (operands) © 1999 Addison Wesley Longman 28

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 1 K of storage. © 1999 Addison Wesley Longman 29

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 © 1999 Addison Wesley Longman 30

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. © 1999 Addison Wesley Longman 31

The Computer’s Core: The CPU and Memory When you purchase a computer, the selection of the CPU is a very important choice. There are two factors that are very important to computer users are: - Compatibility - Speed © 1999 Addison Wesley Longman 32

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. © 1999 Addison Wesley Longman 33

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 (m. Hz). © 1999 Addison Wesley Longman 34

Speed The architecture of a computer determines its speed. • CISC - complex computer

CPU family • CISC – Intel X 86, Pentium – Motorola 680 x 0

Primary Storage: The Computer’s Memory RAM (random access memory): – is the most common type of primary storage, or computer memory. – used to store program instructions and data temporarily – unique addresses and can store in any location – can quickly retrieve information – will not remain if power goes off (volatile). © 1999 Addison Wesley Longman 37

Primary Storage: The Computer’s Memory • ROM (read-only memory): – information is stored permanently on a chip. – contains startup instructions and other permanent data. © 1999 Addison Wesley Longman 38

Buses, Ports, and Peripherals Information travels between components through groups of wires called buses.

Buses, Ports, and Peripherals: – are external devices for receiving input or producing output (keyboard, monitor, and mouse). – communicate with other parts of the system. © 1999 Addison Wesley Longman 40

Buses, Ports, and Peripherals – provide attachment and communication with external devices by means of: slots (for internal attachment) ports (for external attachments) © 1999 Addison Wesley Longman 41