CSCD102

1. CSCD102 INTRODUCTION TO COMPUTER SCIENCE II

2. 3. COMPUTER HARDWARE • 3.1 Objectives • 3.2 Definitions • 3.3 Computer Architecture • Layer Concept • Modular Concept 3.3.1 Simplest (2 layer) 3.3.2 Multi-layer

3. 3.1 Objectives • The student must know the basic terms in computer hardware • Understand the systemic way of problem solution • That the computer is a system • Understand the working of the computer in terms of the hardware architecture using the layer concept and the modular concept • The advantages the two concepts offer in the study of computer systems

4. 3.2 Definitions • System a collection of coordinated components that work together to achieve a well defined goal.

5. 3.2 Definitions • Computer System – -A device that works under the control of stored programs, automatically accepting, storing and processing data to produce information that is the result of that processing. -A device that accepts data in one form and processes it to produce data in another form.

6. 3.2 Definitions • Basic Components / Elements of Computer Systems • input • process • output • store

7. 3.2 Definitions • Basic Functions that Computer Systems perform -Input :- it accepts data from outside for processing within. -Processing:- the computer performs operations on the data it holds within. -Output:- the computer produces data from within for external use -Storage:- the computer holds data internally before, during and after processing.

8. 3.2 Definitions • Computer Architecture : The style of construction and organization of the many parts of a computer system.

9. 3.2 Definitions • Hardware :The general term used to describe all the tangible components ( electronics and mechanical) of the computer system. Examples: - Input devices :- keyboard, mouse, joy stick etc. -Output devices:- printer, visual display unit, plotter etc. -Processor :- Intel Processor, Motorola Processor etc -Storage:- Main Memories/Primary Storage , Mass Storage/ Secondary Storage

10. 3.2 Definitions • Software The general term used to describe all the various programs – intangible - that may be used on a computer system together with their associated documentation. Examples -WINDOWS Operating System -Microsoft WORD -Internet Explorer

11. 3.2 Definitions • Program Is a set of logical instructions that is written in the language of the computer to make the computer perform a specific task.

12. 3.2 Definitions • Stored Program -The computer is only able to obey a program’s instruction if the program has first been stored within the computer. -This implies that the computer must be able to input and store programs in addition to data. -The computer therefore works under the control of stored programs.

13. 3.2 Definitions • Data The raw or basic facts pertaining to an entity or object of interest . Entity or Object of interest = CAR Facts Colour, Registration Number, Chassis Number, Date Manufactured, Number of Passengers, Type etc.

14. 3.2 Definitions • Information Data that has been processed or converted into a more useful or meaningful or intelligible form.

15. Data and information WHAT WILL REPLACE THE ?1 AND ?2 ?1 ?2 PROCESS

16. 3.2 COMPUTER ARCHITECTURE: CONCEPT OF LAYER To study and understand Computer Systems, there are a number of levels to be considered: - Simplest ( 2 layer ) concept - Multi-layer concept

17. Simplest ( 2 layer) The simplest distinction between levels is that between Hardware and Software. • The Hardware is viewed as the lowest and most basic level of the computer onto which a “layer” of Software is added. • The software sits above the hardware, using it and controlling it. • The hardware supports the software by providing the operations the software requires. SOFTWARE HARDWARE

18. Multi-Layered Machine

19. HARDWARE SUBLAYERS • Physical Device Layer Electrical and electronic component layer. The various hardware devices are at this level and are built from simple (discrete) electronic components such as transistors, capacitors and resistors. These components rely on suitable electrical power supplies and operating environments. • (Area of Computer Engineering/Technology )

20. HARDWARE SUBLAYERS • Digital Logic Layer The basic elements at this level can store, manipulate and transmit data in the form of simple binary representations. Gates :- the digital logic elements. A gate is normally constructed from a small number of transistors and other electronic components. AND gate, OR gate, NAND gate, NOR gate, XOR gate etc. Many gates may be combined using (SSI, MSI, LSI, VLSI) onto a single chip to form standard digital logic elements such as :- Adders(full or half), decoders, multiplexers, flip-flops, latches, comparators etc. Standard digital logic elements are combined together to form computer processors, computer memories, and major components of units used for input and output.

21. HARDWARE SUBLAYERS • 3. Microprogrammedlayer and 4. Machine layer The microprogrammed layer interprets the machine language instructions from the machine layer and directly causes the digital logic elements to perform the required operations. The microprogrammed layer is a very basic inner processor and is driven by its own primitive control program instructions held in its own private inner ROM. These program instructions are called microcode and the control program is called a microprogram. The machine layer is the lowest level at which a program can be written and it is only machine language instructions which can be directly interpreted by the hardware.

22. Eg Computer Machines • RISC ( Reduced Instruction Set Computers) • CISC (Complex Instruction Set Computers

23. SOFTWARE SUBLAYERS • 5. Operating System (OS) layer This layer controls the way in which all software uses the underlying hardware. It hides the complexities of the hardware from the other software by providing its own facilities which enable software to use the hardware more simply. It prevents other software from bypassing these facilities so that the hardware can only be assessed directly by the operating system. It provides an orderly environment in which machine language instructions can be executed safely and effectively.

24. SOFTWARE SUBLAYERS • 6. Higher Order Software layer Handles all programs in languages other than machine language which require translation into machine code before they can be executed. Such programs, when translated, rely upon the underlying OS facilities as well as their own machine instructions.

25. SOFTWARE SUBLAYERS • 7. Applications layer This is the computer interface as seen by the end-user. The language of the computer as seen by the end-user.

26. SOFTWARE SUBLAYERS • Virtual Machine (VM) Given the layer arrangement of the computer architecture, the underlying computer as viewed from each layer is sometimes referred to as VM. The OS is a VM to the Higher order software layer. The Higher Order software layer is VM to the Application layer.

27. PHYSICAL ORGANIZATION OF THE COMPUTER SYSTEM • How the complete microelectronic components are deployed. Design and Build Approach: The Principle of Modular Construction Most computer manufacturers construct their computers from varied combinations of standard components. For example, many different microcomputers contain the same microprocessors.

28. PHYSICAL ORGANIZATION OF THE COMPUTER SYSTEM • Standard components are much easier to interconnect if the means of interconnection is also standardized. One important method for doing this is using “buses”.

29. PHYSICAL ORGANIZATION OF THE COMPUTER SYSTEM • BUS A Bus is a collection of parallel electrical conductors called “lines” onto which a number of components may be connected. Connections are made at points along the length of the bus by means of connectors with multiple electrical contacts.

30. PHYSICAL ORGANIZATION OF THE COMPUTER SYSTEM (MODULAR) GENERAL PURPOSE BUS OUTPUT UNITS PROCESSOR MAIN MEMORY INPUTUNITS

31. BUS • Two Basic Types of Bus • Internal Buses Are used within the processor and are integral parts of its construction. • External Buses Are used to connect separate hardware elements together, e.g. connecting the processor to main memory.

32. BUS • Use of Bus Buses may be used to convey: • Data signals ( data bus / lines) • Data address signals ( address bus / lines) • Control signals ( control bus / lines ) • power

33. BUS • Form-Factor/ Size of the Computer Three different forms of construction • Single-chip computers • Single-board computers • Multiple-board, bus-based computers

34. BUS • Single-chip computers– those found in such devices as • Cameras • Watches • Intelligent micro-machines • The processors are specialized, they are programmed to do specific task , they are not immediately recognizable.

35. BUS • Single-board computers– are • usually much bigger than single-chip computers • still relatively small • they are constructed on printed circuit boards (PCB)

36. BUS • Single-board computers– are Two broad categories of Single-board • Small general-purpose microcomputers: for example Personal Computers and its family. • Small special-purpose computers : often used for applications involving the control of physical processes.

37. BUS • Single-board computers– are Two broad categories of Single-board • Small general-purpose microcomputers: for example Personal Computers and its family. • Small special-purpose computers : often used for applications involving the control of physical processes.

38. BUS • Multiple-board, bus-based computers-are usually • General-purpose computers • Normally too large to fit onto a single board Function oriented boards are connected by plugging them into individual slots on one or more general-purpose buses. One board may contain the processor, another board may contain the main memory and so on Example include the main frames and the minicomputers Motherboard – the primary board for the processor and other main components are slotted into it

39. recall • Main components of Digital Logic Layer ( DLL )

40. recall • Mention examples of standard digital logic devices.

41. recall • Adders • Decoders • Multiplexers • ……. These are the standard digital logic devices. They are combined together to form computer modules Buses provide the interconnections.

42. recall • Mention the discrete components of logic devices

43. recall • The logic gates : AND, OR ……………………… • Draw the Logic gates AND , OR

44. PHYSICAL ORGANIZATION OF THE COMPUTER SYSTEM (MODULAR) • I / O BUS MEMORY BUS INPUTUNITS OUTPUT UNITS PROCESSOR MAIN MEMORY

45. TWO BUSES • I / O BUS MEMORY BUS INPUTUNITS OUTPUT UNITS MAIN MEMORY PROCESSOR

46. Two Bus arrangement • MOST architectures are based upon TWO BUSES and follow one of the two basic architectures shown above.

47. Two Bus arrangement • In both cases the bus used for data transfers between memory and the processor is separate from the bus used by input and output units.

48. Two Bus arrangement • The data transfers between memory and the processor use a faster bus than that of the slower devices used for input and output.

49. Two Bus arrangement used in larger Microcomputers and many Minicomputers • The processor has direct connections to both buses. • Data only passes between memory and the I/O units via the processor.

50. Two Bus arrangement used in larger Microcomputers and many Minicomputers • I / O BUS MEMORY BUS INPUTUNITS OUTPUT UNITS PROCESSOR MAIN MEMORY