CSCD 102 INTRODUCTION TO COMPUTER SCIENCE II 3

CSCD 102 INTRODUCTION TO COMPUTER SCIENCE II

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. 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

3. 2 Definitions • System a collection of coordinated components that work together to achieve a well defined goal.

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.

3. 2 Definitions • Basic Components / Elements of Computer Systems – input – process – output – store

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.

3. 2 Definitions • Computer Architecture : The style of construction and organization of the many parts of a computer system.

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

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

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.

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.

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.

3. 2 Definitions • Information Data that has been processed or converted into a more useful or meaningful or intelligible form.

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

3. 2 COMPUTER ARCHITECTURE: CONCEPT OF LAYER To study and understand Computer Systems, there a number of levels to be considered: - Simplest ( 2 layer ) concept - Multi-layer concept

Simplest ( 2 layer) SOFTWARE HARDWARE 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.

Multi-Layered Machine 7. 6. Application Layer SOFTWARE High Order Software 5. Operating System Layer 4. Machine Layer 3. Microprogrammed Layer 2. 1. HARDWARE Digital Logic Layer Physical Device Layer

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 )

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.

HARDWARE SUBLAYERS • 3. Microprogrammed layer 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.

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

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.

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.

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.

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.

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.

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”.

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.

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

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.

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

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

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.

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

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.

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.

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

recall • Main components of Digital Logic Layer ( DLL )

recall • Mention examples of standard digital logic devices.

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

recall • Mention the discrete components of logic devices

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

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

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

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

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.

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.

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.

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

Two Bus arrangement used in larger Minicomputers and Mainframes • The processor only accesses data via the memory bus. • The processor delegates some of its detailed I/O controlling powers to subsidiary peripheral processors ( I/O channels )

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

Speed Issues • The bus arrangement and bus width affects the speed of the system and the aim is to • Maximize the use of the processor by freeing it of the burden of controlling low level I/O operations. • To maximize the speed and efficiency of I/O data transfers to and from memory. • Use wider bus width to transfer data. This may vary from 8 -bits, 16 -bits, to 32 -bits , 64 -bits. • Generally the mainframes have lager bus widths than the minicomputers and more so than the microcomputers.

THE PROCESSOR • The processor consists of – The Control Unit (CU) – The Arithmetic and Logic Unit ( ALU) ALL components of the processor are wholly electronic

THE PROCESSOR • Functions of the Processor – To control the use of main storage to store data and instructions – To control the sequence of operations – To give commands to all parts of the computer system – To carry out processing

THE PROCESSOR • The Processor controls the input of data and its transfer into main storage, processes data, and then sends the result to output units. At all stages data transmission is electronic

BUS (multiple) CONNECTIONS • MBR POWER CONTROL BUS DATA BUS MAIN MEMORY ADDRESS BUS PROCESSOR MDR MAR

THE PROCESSOR • Registers are special-purpose temporary-storage locations within the processor or other devices they are separate from the locations in main memory, though similar in structure

THE PROCESSOR • Relation between Buses and Registers MDR = Memory Data Register MBR = Memory Buffer Register MAR = Memory Address Register

THE PROCESSOR • Relation between Buses and Registers – All data and instructions pass in and out of the PROCESSOR through MDR – All data and instructions pass in and out of the MAIN MEMORY through MBR

THE PROCESSOR • Location address (MAR) Prior to each transfer between the processor’s MDR and main memory’s MBR, the exact source or destination of the data in main memory must be specified. This is done by loading the appropriate location address into the MAR.

THE PROCESSOR • Location address Main memory receives this address information via the address bus. It also receives control signals from the processor via the control bus which it is able to decode into commands for it to save or retrieve data.

DETAILS OF A PROCESSOR A L U RESULT OPERAND STATUS IR CONTROL UNIT DATA BUS MAR ARO AR 1 AR 2 AR 3 AR 4 AR 5 AR 6 AR 7 DRO DR 1 DR 2 DR 3 DR 4 DR 5 DR 6 DR 7 MDR INTERNAL BUS ADDRESS BUS EXTERNAL STATUS PC CONTROL DATA EXTERNAL CONTROL CLOCK POWER LINES

THE PROCESSOR • Control Unit Function it co-ordinates and controls all hardware operations peripheral units main memory the processor

THE PROCESSOR • Control Unit How it Operates The two stage operation Fetch-Execute Cycle Assume that after the ROM instructions have been executed the MAR has been loaded with the address of the next instruction to be performed

THE PROCESSOR • Control Unit The CU causes the requisite instruction to be fetched from MM via the MDR and placed in the IR (Current Instruction Register) When MM receives an appropriate signal from the CU, it transfers the instruction, whose address is specified in the MAR, into the processor’s MDR via the Data Bus

THE PROCESSOR • Control Unit The CU causes the requisite instruction to be fetched from MM via the MDR and placed in the IR (Current Instruction Register) When MM receives an appropriate signal from the CU, it transfers the instruction, whose address is specified in the MAR, into the processor’s MDR via the Data Bus

HARDWARE AND SOFTWARE INTEGRATION • FIRMWARE this is program encoded in a ‘hardware’ form usually in Read Only Memory (ROM) used to provide very basic services at a functional level just above the hardware

HARDWARE AND SOFTWARE INTEGRATION • ROM CHIPS is a hardware piece it is referred to as Read Only Memory because it is either impossible or difficult to write to sometimes referred to as Non-Volatile ROM (NVROM) because any data stored in ROM remains there even if the power is turned off

HARDWARE AND SOFTWARE INTEGRATION • STARTUP INSTRUCTION A personal computer’s start-up instruction (the software that boots the system) is put in ROM

HARDWARE AND SOFTWARE INTEGRATION • STARTUP INSTRUCTION A personal computer’s start-up instruction (the software that boots the system) is put in ROM the MOTHERBOARD ROM

HARDWARE AND SOFTWARE INTEGRATION • MOTHERBOARD ROM NORMALLY contains four main Programs in General-purpose computer systems: – – CMOS BIOS POST BOOTSTRAP LOADER

HARDWARE AND SOFTWARE INTEGRATION • CMOS Complementary Metal-Oxide Semiconductor set up this is a menu driven application that allows the user to set System Configuration parameters options security settings and preferences

HARDWARE AND SOFTWARE INTEGRATION • CMOS it is a special kind of small-scale memory embedded in a chip soldered to the motherboard and powered by a battery

HARDWARE AND SOFTWARE INTEGRATION • CMOS function it maintains a record of – – – date and time how much memory your PC has which hardware devices are attached

HARDWARE AND SOFTWARE INTEGRATION • CMOS importance it is only by the reference to CMOS during the power-up procedure that the computer knows it is a computer at all without CMOS the computer would have to laboriously re-identify itself every time

HARDWARE AND SOFTWARE INTEGRATION • CMOS require some configuration at the outset this is done through the BIOS you can configure Password = whether required after POST Drive Order = the order that POST checks drives for the OS Memory = how much RAM is installed on system

HARDWARE AND SOFTWARE INTEGRATION • CMOS Drive Type = the type of hard drive attached Display = specify the monitor type

HARDWARE AND SOFTWARE INTEGRATION • BIOS Basic Input/Output System a series of device driver programs designed to present standard interface to the basic system hardware importantly hardware that must be active during the boot process

HARDWARE AND SOFTWARE INTEGRATION • BIOS ROM This is a separate chip on the motherboard that contains a set of instructions and drivers intended to get the computer hardware (Layer 1) up and running before the OS (Layer 2) kicks in

HARDWARE AND SOFTWARE INTEGRATION • BIOS ROM function most important function is to boot up the system when you first turn on the system, its main system memory is empty, and it needs to find instructions to tell it what to do

HARDWARE AND SOFTWARE INTEGRATION • BIOS ROM function these instructions are found within the BIOS program – – SETUP Program POST Program

HARDWARE AND SOFTWARE INTEGRATION • BIOS ROM SETUP Program lets you manually configure the information held in CMOS to access its Setup program you must press a specific key or key combinations as the computer is powering up

HARDWARE AND SOFTWARE INTEGRATION • BIOS ROM POST Program a series of (Power-On Self Test) - test routines that ensure the system components are operating properly

HARDWARE AND SOFTWARE INTEGRATION • BIOS ROM POST Program function the very first thing a computer does when it is powered on is BIOS is loaded into memory

HARDWARE AND SOFTWARE INTEGRATION • BIOS ROM POST Program function BIOS then performs a routine known as POST check again that it still has processor, memory, motherboard, etc.

HARDWARE AND SOFTWARE INTEGRATION • POST fatal errors if POST finds a serious problem or fatal error it throws beep and halt the computer in its tracks this can help to identify the specific Layer 1 component causing the problem

HARDWARE AND SOFTWARE INTEGRATION • Check order the layer 1 components are checked in the order in the table

HARDWARE AND SOFTWARE INTEGRATION Component Description of Test • Check order. Halt without displaying any message ROM BIOS A series of checksums are computed and if they do not match , Processor system halts DMA controller System halts Interrupt Controller System gives a long beep followed by a short beep, system halts Timing Chip System halts BASIC ROM If the system has built in BASIC compiler Video Card System gives a long beep followed by two short beeps If test succeeds ROM BIOS gets copied into RAM memory Expansion Boards are initialized, ROM copied to RAM memory Counts and test RAM by writing a bit to each memory bit Keyboard Presence of keyboard any stuck keys Floppy Drive Signal is sent to adapter to activate floppy drive motor

HARDWARE AND SOFTWARE INTEGRATION • Plug and Play if the BIOS supports plug and play standards it will detect and configure plug and play devices

HARDWARE AND SOFTWARE INTEGRATION • BOOTSTRAP LOADER the routine that first scan`s the secondary storage devices looking for an OS to load often the floppy disk is scanned first ( or removable drives ) then followed by the hard disk as determined by the setup why?

HARDWARE AND SOFTWARE INTEGRATION • System Software oriented to the needs of the hardware and facilitates the development and running of applications

HARDWARE AND SOFTWARE INTEGRATION • System Software comprises Firmware Operating System Utilities Programming Languages( sometimes)

HARDWARE AND SOFTWARE INTEGRATION • OS Structure APPLICATION PROGRAMS SYSTEM PROGRAMS Compilers, Assemblers, Linkers etc USER INTERFACE OS HDW PROCESS MANAGEMENT MEMORY MANAGEMENT I/O MANAGEMENT FILE MANAGEMENT CPU MAIN MEMORY I/O DEVICES SECONDARY STORAGE COMMUNICATION MANAGEMENTT COMMUNICATION DEVICES

HARDWARE AND SOFTWARE INTEGRATION OS LAYERS AND RELATION TO USER, APPLICATIONS , HARDWARE USER COMMAND KERNEL HDW SERVICE APPLICATION PROGRAM

OS • OS FUNCTIONS INCLUDE: Process Control File control Secondary Storage control I/O device control User control

OS • OS Examples: WINDOWS UNIX LINUX REDHAT UBUNTU DOS

OS • OS Model: The Command Layer Service Layer Kernel

OS • OS The Command Layer is the user interface to the OS Function it provides an interface that allows the user to give commands to operate the computer system

OS • OS Service layer is that part of the OS that provide key functions to the computer system e. g Application management Computer Browser Domain Name Servers Event Log Telnet Security Accounts Manager

OS • OS Kernel ( Supervisor/ Executive) is that part of the OS that remains in main storage permanently during the running of the computer; it is the controlling part of the OS Function: - it controls the running of all other programs