Discovering Computers 2012 Your Interactive Guide to the

Discovering Computers 2012 Your Interactive Guide to the Digital World Edited by : Noor Alhareqi

The System Unit • The system unit is a case that contains electronic components of the computer used to process data. • Made of metal or plastic to protects the internal components from damage. • All computers have a system unit. It is available in variety of shapes & sizes. Page 210 Figure 4 -1 Discovering Computers 2012: Chapter 4 2

Discovering Computers 2012: Chapter 4 3

The System Unit • The inside of the system unit on a desktop personal computer includes: Drive bay(s) Power supply Sound card Video card Processor Memory Page 211 Figure 4 -2 Discovering Computers 2012: Chapter 4 4

Motherboard • The motherboard is the main circuit board of the system unit. • Contains expansion slots, processor chips, and memory slots • Sometimes called a system board Page 212 Figure 4 -3 Discovering Computers 2012: Chapter 4 5

Motherboard • Most computers use integrated circuits also called chips , for their CPU and main memory. • Memory chips are installed on memory module( card) that fit in a slot on the mother board. • What is a chip? • Small piece of semi-conducting material on which integrated circuits (IC) are etched. • IC contain many microscopic pathways capable of carrying electrical current. • Each IC can contain millions of elements such as resistors, capacitors, transistors. Next

Processor • The processor, also called the central processing unit (CPU), interprets and carries out the basic instructions that operate a computer – Contain a control unit and an arithmetic logic unit (ALU) that work together to perform processing operations Multi-core processor Page 213 Dual-core processor Discovering Computers 2012: Chapter 4 Quad-core processor 7

Processor Page 213 Figure 4 -4 Discovering Computers 2012: Chapter 4 8

Processor • The control unit is the component of the processor that directs and coordinates most of the operations in the computer. – Handles the transmission of data into and out of the CPU and supervises its overall operations. – Its interprets each instruction issued by a program & then initiates the appropriate action to carry out the instruction. • The arithmetic logic unit (ALU) performs arithmetic, comparison, and other operations. Page 214 Discovering Computers 2012: Chapter 4 9

Processor • For every instruction, a processor repeats a set of four basic operations, which comprise a machine cycle Page 215 Figure 4 -5 Discovering Computers 2012: Chapter 4 10

Processor The processor contains registers, that temporarily hold data and instructions The system clock controls the timing of all computer operations Page 216 Discovering Computers 2012: Chapter 4 11

Processor Registers • The registers are special storage areas in the CPU. • Their function is to hold instructions, data values, memory addresses of both the instructions and data. • There are 4 basic types of it: CU, ALU • Instruction register hold instruction • Address register hold address of( data , next instruction ). • Storage register store data retrieved from main memory prior to processing. • Accumulator store the results of arithmetic & logic operations Discovering Computers 2012: Chapter 4 12

Processor System clock • It generates regular electronic pulses , or ticks, that control the timing of all computer operations ( i. e. set operating pace of components of system unit) • Pace of system clock is clock speed. Most clock speeds are in the gigahertz (GHz) range (1 GHz = one billion ticks of system clock per second). Discovering Computers 2012: Chapter 4 13

Processor • Most current personal computers support pipelining – Processor begins fetching a second instruction before it completes the machine cycle for the first instruction Pages 215 – 216 Figure 4 -6 Discovering Computers 2012: Chapter 4 14

Processor • Parallel processing uses multiple processors simultaneously to execute a single program or task – Massively parallel processing involves hundreds or thousands of processors Page 220 Figure 4 -11 Discovering Computers 2012: Chapter 4 15

Processor • The leading manufacturers of personal computer processor chips are Intel and AMD Pages 216 – 217 Figure 4 -7 Discovering Computers 2012: Chapter 4 16

Processor • Determine how you plan to use a new computer before selecting a processor Page 218 Figure 4 -8 Discovering Computers 2012: Chapter 4 17

Processor • A processor chip generates heat that could cause the chip to burn up • Require additional cooling – Heat sinks – Liquid cooling technology Pages 219 - 220 Figures 4 -9 – 4 -10 Discovering Computers 2012: Chapter 4 18

Data Representation Analog signals are continuous and vary in strength and quality Digital signals are in one of two states: on or off • Most computers are digital recognize only two discrete states: on or off. • Use a binary system to recognize two states • Use number system with two unique digits: 0 and 1, called bits (short for binary digits) Page 221 Discovering Computers 2012: Chapter 4 19

Data Representation A computer circuit represents the 0 or the 1 electronically by the presence or absence of an electrical charge Page 221 Figures 4 -12 – 4 -13 Eight bits grouped together as a unit are called a byte. A byte represents a single character in the computer ( numbers, upper or lower case letters, or punctuation marks) Discovering Computers 2012: Chapter 4 20

Data Representation • The different combinations of 0 s and 1 s are defined by patterns called a coding schema. • There are two coding schemas used to represent data Ø ASCII—American Standard Code for Information Interchange [Personal Computers – PCS] Ø EBCDIC—Extended Binary Coded Decimal Interchange Code [Mainframes, Mini-computers] Page 221 Figure 4 -14 Discovering Computers 2012: Chapter 4 21

Data Representation • ASCII is the most widely used coding scheme to represent data Page 221 Figure 4 -14 Discovering Computers 2012: Chapter 4 22

Data Representation Page 222 Figure 4 -15 Discovering Computers 2012: Chapter 4 23