Computer Architecture & Operating System [O.S.]

1. Computer Architecture & Operating System [O.S.] • Architecture : Functions as performed by a Computer System. • Organization : Hardware blocks of a Computer System that helps to implement the Architecture. - CPU. - Memory ( Main & Secondary). - Input & Output Peripherals. • Operating System : A System Software that helps all type of users to operate a computer System. CS43051_2k5_ PSD_Basic_Org

2. The Functions of a Computer • It is a general purpose, user programmable, [ A program :Meaningful Group of instructions written in a specific language aimed to do a specific task.] electronic gadget capable of doing the following tasks : • Data Processing (Numeric & Non Numeric) with high degree of accuracy at a pretty high speed. • Storage of huge amount of information of various types {Text (in various formats) , Picture, Audio, Video} with reasonably high access speed [Information Bank]. • Communication Gateway [ Link to the World]. CS43051_2k5_ PSD_Basic_Org

3. Computer Vs. Other Electronic Gadgets • Full User programmability : Under some support environment. Like do not divide if the divisor is 0can be achieved through programming in a computer but such a thing cannot be achieved in a calculator /organizer. • Wide ConnectivityOptions: To other computers and various types of peripherals. • Ease of upgradeability: By installing new packages , connecting state of the art peripherals, enhancing memory etc. • Downward Compatibility : Even after several phases of up-gradation, almost all computer systems do provide support for several old versions of Hardware as well as software . This enables investments made at any stage of a computer system useful and effective for many years to come. CS43051_2k5_ PSD_Basic_Org

4. Data Processing Activity of any Typical Computer (achieved by executing some program) • Numeric Operations involving manipulation of Integers and Floating Point Numbers that includes very large values too (achieved throughSpecial Application Programs) . • Logical Operations like comparing two items. 3.Non Numeric Operations that includes among all things the following : 3a) Arranging Data Items like preparation of merit list. 3b) Manipulating Pictures & Graphics. 3c) Multimedia applications ( Audio, Video, Graphics, Video) 3d) Create, format, send & receive messages of various forms. CS43051_2k5_ PSD_Basic_Org

5. The Building Blocks of any Computer System • The Central Processing Unit [ C.P.U.] performs processing & control. • The Memory System ( Internal as well as Peripheral Devices) the storage repository. • The various Input & Output Peripheral Devices. • The links/connections between these Components [ The various Bus ]. CS43051_2k5_ PSD_Basic_Org

6. The Operating System The Operating System is a Modular, Expandable Program which is pre-designed & stored in the Memory System that , when executed by the CPU, makes all the components of a Computer functionin unisonas well asenables real world users to interact with the Computer System. CS43051_2k5_ PSD_Basic_Org

7. The Memory System The Common Storage Repository of any Computer System The Memory System of any Computer acts as the Common Storage repository for the following : • The Operating System includes various Drivers , Resource Managers, Command Interpreters & Graphic User Interfaces (GUIs). • Other System Programs like Translator ( Compiler, Assembler) , Linker, Loader, System Libraries. • Various Application Modules like MS-Office, Internet Browsers. • Data in various forms ( Text, Pictures, Images, Audio & Video) CS43051_2k5_ PSD_Basic_Org

8. Computer Components- 1The Central Processing Unit [C.P.U.]Structure Outline Each & every computer MUST carry out some form of processing , hence it must possess : • A Processing Element / Processing Unit / Processor {Arithmetic, Logical, Manipulation of Messages} [ The Arithmetic Logic Unit (ALU) ]. • Some form of electronic local storage / Registers [ Scratchpad ]. • The processing tools i.e. the instructions available for processing . These instructions constitute any program framed to accomplish any kind of processing implemented through the Control Unit . • Proper sequencing the processing steps / instructions as well as controlling the various components to achieve the desired result through the Control Unit. • Interface to the other components of the Computer ( achieved through Registers & Control Unit ). The above are closely linked together hence are all encapsulated into the C.P.U. { Central Processing Unit}. CS43051_2k5_ PSD_Basic_Org

9. The Functions of the CPU The Central Processing Unit performs the following tasks by executing Instructions of some specific Operating System Modules / System program stored in the Memory System. 1) Controlling all peripheral devices. [ Relevant Device Driver Program(s)]. 2) Communicating with all types of Remote Devices. [ Network Protocol Program (s) acting on Network Cards ] 3) Recognizing user commands [ Command Interpreters / GUI (Graphic User Interface) ]. 4) Inputting Data [ Device Driver of the O.S.]. 5) Producing Output (on screen /or on printer) after obtaining Data from Main/Secondary Memory.[Device Driver of the O.S.] 6) Performing arithmetic & logical operations.[ As per Specified Instruction(s) of the executing program (s)]

10. The Components of the C.P.U. • Arithmetic & Logical Processing Unit [ The A.L.U]. • Associated Data Storage Components / Scratch Pad Storage. Electronic Storage (The Registers). • The implementation of the Instruction Set as well as the unit that controls & sequences all operations in accordance with the supported Instruction Set [ The Control Unit ] . • The interface with other components of a Computer [Special Purpose Registers along with associated controls ]. ( All will be illustrated in due course ). CS43051_2k5_ PSD_Basic_Org

11. The Components of the CPU Storage & Interface Registers ALU Control Unit CS43051_2k5_ PSD_Basic_Org

12. The CPU Performance Parameters - 1 N.B: All the activities of any Computer System are being carried out by the CPU by executing some machine level /low level instruction. 1. CPU Speed : Each machine instruction takes a definite time to complete execution. This time is measured in terms of the Number of CPU Clock Periods needed to execute that instruction ( The Instruction Latency). Hence one way to measure the CPU speed is Number of Instructions executed / second (termed as the Throughput) . Typical unit isMIPS (Millions of Instructions per second) or MFLOPS (Millions of Floating point Operations performed per second.) However one normally finds the CPU Clock frequency as rough estimate of its speed i.e. higher the clock frequency higher will be the CPU speed. But in actual terms speed will be affected depending on the most frequently used instructions hence the Throughputhappens to be a more fair estimate of the CPU speed estimated by executing some benchmark programs . CS43051_2k5_ PSD_Basic_Org

13. The CPU Performance Parameters - 2 2. CPU Processing Power : The Operand Size (in bits) it can handle at one go i.e. in a single machine instruction normally. This is directly related to its ALU ( Arithmetic Logic Unit a purely combinational Circuit) width. e.g. Pentium is a 32 Bit CPU Any Machine level instruction of a Pentium Processor can handle 32 bit operands or Pentium contains 32 bit Integer ALUs. N.B: This Operand Sized based classification is interesting in the sense that any n bit CPU can also be used to handle larger sized data provided one writes proper programs to achieve that which gets translated into n bit processing instructions by the Translator Program (The Compiler). CS43051_2k5_ PSD_Basic_Org

14. Computer Components – 2 [ The Memory ] • Memory : Essential to create any form of Information Bank/ Common Storage Repository ( as illustrated earlier). Wide range & types of Memory & Storage Media are available/ in use now –a –days . CS43051_2k5_ PSD_Basic_Org

15. Generalized Memory Structure • Large Data Storage repository. • Structure is NOT dictated by what is stored in that memory (Content Independent). • Several access mechanism modes exists to access it’s content . • Any memory can be thought to be composed of several individuallyaddressable blocks each of which contains some data (generic term) item. CS43051_2k5_ PSD_Basic_Org

16. User Requirement/ Ideal View point of the Computer Memory • Should be Infinite Sized. • Should possess High Speed of access. • Should be of Low Cost . • Has to be Reliable. • Must be Expandable with little or no affect on the existing system configuration. • Must be flexible & adaptable to change in size as well as to compatibility with new emerging technologies. CS43051_2k5_ PSD_Basic_Org

17. Classification of Memory Classification A ( Media Types). • Electronic [ ROM, EPROM, Static RAM, Dynamic RAM, Flash , Memory Stick]. • Magnetic [ Hard Disk, Flex Disk, Tape, DAT]. • Optical [CD-R/ -RW, DVD-R/RW, DVD-RAM, Blue-Ray DVD, HD DVD]. Classification B ( Data Retention Property). • Volatile. [ Electronic ] • Non Volatile. [ Flash, Magnetic , Optical]. Classification C ( Alterability Property). • User Alterable.[ RAM, Flash, Disk, Tape, DAT, CD-RW, Blue-Ray / HD / Ordinary DVD-RW] • Non Alterable [ROM, EPROM, Flash, CD, DVD]. Classification D ( CPU Proximity & Accessibility, Most System Relevant). • Register. {Electronic, Volatile, User Alterable}. • Cache. {Electronic, Volatile, Transparent to User} • Main / Primary. {Electronic, Volatile, User Alterable}. • Secondary ( Some External) . {Flash, Magnetic Disks & Tapes, Optical, Non Volatile, Some User Alterable}. CS43051_2k5_ PSD_Basic_Org

18. Peripheral & Remote Devices Peripherals/ Peripheral Devices : All those Devices that lie in the Periphery of the CPU. All Peripheral Devices are connected to the CPU through several Buses (as illustrated earlier) and are controlled by the CPU through some Device Driver program (s) [ part of the Operating System]. Remote Devices : Those which are far away from the current CPU/ Computer System connected through the Network Interface. CS43051_2k5_ PSD_Basic_Org

19. Input Output Peripherals • Helps to establish link between computer / cyber world & Real World. Various forms of I/O Peripherals exists. • Common Input Peripherals : Key board, Mouse. • Common Output Peripherals : Video Monitor, Printer. CS43051_2k5_ PSD_Basic_Org

20. Input Peripheral Devices and their Functions ( Architectural Aspects) • These are employed to feed data , program, picture, commands to the Computer System. A few commonly used devices are the following : • Keyboard ( The earliest and still most commonly used Input Device).: To type in Commands and/or Data [Alphabets, Digits, Symbols etc.] • The Mouse : Commands are given by clicking its left/right button. It works in a Graphic Environment where user is given option to select among several Options in a menu by moving mouse button on to that item and clicking on that. CS43051_2k5_ PSD_Basic_Org

21. Output Peripherals and their Functions- 1 • Output Peripherals are responsible for providing some form of response/result to the user. Commonly used Output peripheral devices are : • Visual Display Unit (VDU) Screen / Monitor : Is used to display the following • Anything typed in via keyboard. • The various menus available to the user. • The response generated by the system to various user commands in some way. • The result generated by running various programs/ packages. CS43051_2k5_ PSD_Basic_Org

22. Output Peripherals and their Functions - 2 2. Printers : Used to produce printed Outputs / Hard Copy. Various types of printers : • Impact Printers : Where there exists a physical printing Mechanism/ print head that strikes on the paper & ink ribbon to make an impression on the Paper. These mostly print in Black . Examples of such printers are Dot Matrix , Line , Band etc. • Non Impact Printers : Here there exists no physical printing heads rather printing is done by electronic/electrostatic mechanism that regulate the flow of ink/toner which are electro statically deposited on the paper. These can print both in Monochrome (black) as well as in Color. Commonly used printers are Inkjet, Desk jet, Laser etc. Graphic Printers like Dot Matrix, Inkjet, Desk Jet, Laser can print both text as well as pictures while Line Printer, Band Printer can only print characters . But these are high speed & rugged compared to graphic printers . CS43051_2k5_ PSD_Basic_Org

23. Peripheral Interfaces - 1 • Most of the peripheral devices helps in establishing human interface to the computer System (mainly CPU & Memory). • Each of the peripheral differs in characteristics from each other as well as from the electronic parts (CPU & Memory) in terms of electrical features and operating speed. • Some kind of programs are required to control all the various peripherals (Device Drivers) . • Users interact with any computer either by some command or alternately by mouse click . Hence some form of command interpreter or Graphic User interface [GUI] is needed . • These device driver programs as well as Command Interpreter & GUI forms part of the existing Operating System . CS43051_2k5_ PSD_Basic_Org

24. Peripheral Interfaces - 2 • All peripherals must possess the following things : a) An Electronic Peripheral Interface that helps to isolate the CPU & Main Memory from the diverse world of peripherals. b) CPU – Peripheral connectivity is established through the following components : 1) Electronically addressable Command Register (Write Only). 2) Electronically addressable Status Register (Read Only). 3) Electronically addressable Local Data Buffer (Read/Write). CS43051_2k5_ PSD_Basic_Org

25. BUS : The Connection Gateway • Group of Electrical Lines ( cables and/or PCB Tracks OR both ) performs a particular task in unition. • Helps to connect the Different Components of any Computer System. CS43051_2k5_ PSD_Basic_Org

26. CPU – External World Connectivity - 1 1) CPU must be able to address each device interface as well as each memory location. This Address is sent via a group of electrical lines / PCB Tracks termed as the Address bus. 2) CPU sends / receives datato / from the device interface & memory through a separate group of lines termed as Data Bus. 3) CPU sendsCommand to / or reads Device Status from the device interface / memory via a 3rd group of lines known as the Control Bus. CS43051_2k5_ PSD_Basic_Org

27. The Different Buses Address Bus - Group of lines that is used to carry address information from the CPU to the concerned device(s). Address is one that helps the CPU to select one among many devices. Hence it is unidirectional. Data Bus - The group of lines used to carry data/information from the device to CPU &vice versa. It is always bi-directional. Control Bus – The group of lines that enables the CPU to control various activities by sendingappropriate commands as well as monitor status of the concerned device e.g. Read Signal, Write Signal,Status Set Signal. Each bus consists of a number of lines, which is represented in a compact manner. Bi Directional Bus composed of 32 Lines 32 CS43051_2k5_ PSD_Basic_Org

28. Memory Bus & I/O Bus • As has already been mentioned , Peripherals presents a much larger diverse interface scenario than the Memory. • The entire Memory hierarchy interacts with the CPU through some pre-specified protocol. • Whereas, large diverse nature of Peripheral Interfaces demands a much larger variety of interface protocols . • This demands different set of Buses , namely, I/O Bus and Memory Bus to connect peripherals and Memory respectively with the CPU. • However, any type of BUS, in principle , must essentially compose of ADDRESS, DATA & CONTROL Buses only differing in signal level & layout. CS43051_2k5_ PSD_Basic_Org

29. Oversimplified Bus Level Organization CS43051_2k5_ PSD_Basic_Org