Edited by : Noor Alhareqi

1. Edited by : Noor Alhareqi

2. The System Unit • The system unitis 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. Discovering Computers 2012: Chapter 4 Page 210 Figure 4-1

3. Discovering Computers 2012: Chapter 4

4. The System Unit • The inside of the system unit on a desktop personal computer includes: Discovering Computers 2012: Chapter 4 Page 211 Figure 4-2

5. 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 Discovering Computers 2012: Chapter 4 Page 212 Figure 4-3

6. Next 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.

7. 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 Discovering Computers 2012: Chapter 4 Page 213

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

9. Processor • The control unitis 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. Discovering Computers 2012: Chapter 4 Page 214

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

11. Processor Discovering Computers 2012: Chapter 4 Page 216

12. 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

13. Processor Systemclock • 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

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

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

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

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

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

19. Data Representation Discovering Computers 2012: Chapter 4 Page 221

20. Data Representation A computer circuit represents the 0 or the 1 electronically by the presence or absence of an electrical charge 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) Page 221 Figures 4-12 – 4-13 Discovering Computers 2012: Chapter 4

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

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

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