Transcript Unit1x

C_ITCO011/C_ITCO111
LECTURER: E.DONDO
UNIT 1:
INTRODUCTION TO COMPUTER SYSTEMS
Definition
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A computer is a device that accepts data and manipulates it
for some result based on a program or sequence of
instructions on how the data is to be processed.
A computer therefore basically:
◦ takes input.
◦ processes such according to stored instructions.
◦ produces results as output.
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A computer consists of :
◦ hardware (devices, such as a hard drive, that are physically connected
to the computer or components that can be physically touched) and
◦ software (a collection of computer programs and procedures that
perform some task on a computer system.)
Computer characteristics:
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It responds to a specific set of instructions in a
sequenced manner
It can execute a pre-recorded list of instructions (a
program/application)
It can quickly process, store and retrieve large
amounts of data in a structured format
It can perform complex and repetitive procedures
quickly, precisely and reliably.
Hardware components of a computer
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Central processing unit (CPU):
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Memory :
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Mass storage :
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Input devices:
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Output devices:
◦ it is the heart of a computer.
◦ this is the component that actually executes instructions
organized in programs (software), which tell the computer what to
do.
◦ this enables a computer to store data, programs and intermediate
results (e.g. RAM, ROM, cache)
◦ provides fast, expensive, short-term memory.
◦ this enables a computer to permanently retain large amounts of
data and programs.
◦ common storage devices include cds, hard disk and tape drives.
◦ provides slow, cheap, long-term memory.
◦ these are, usually, a keyboard and mouse;
◦ an input device is a conduit through which data and instructions
enter a computer.
◦ these can be a display screen, printer or other device that allows
you to visualize what the computer has accomplished
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This can be done according to:
a) Principles of operation
i. Analogue computers
ii. Digital computers
iii. Hybrid computers
b) Configuration
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Super-computers
Mainframe computers
Mini-computers
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Micro-computers
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Analog computers
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Digital computers
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Hybrid computers
◦ They work on a continuous range of values.
◦ They give approximate results as they deal with quantities that vary
continuously.
◦ They deal with physical variables, such as voltage, pressure, temperature,
speed, etc.
◦ They operate on digital data, such as numbers.
◦ They use a binary number system, in which there are only two digits; 0
and 1.
◦ Each digit (0 or 1) is referred to as a ‘bit’.
◦ They can give results with more accuracy and at a faster rate.
◦ A combination of the desirable features of analog and digital computers.
◦ They are designed using digital circuits, in which there are two levels for
an input or output signal.
◦ These two levels are known as ‘logic 0’ and ‘logic 1’.
◦ They can be used to solve complex problems in engineering and
technology by the application of varying numerical methods.
- This is a classification of digital computers based on performance, size,
cost and capacity.
Super-computers
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these are extremely fast computers that can perform and process billions of
instructions per second
they are normally used to solve intensive numerical computations e.g.
◦ stock analyses,
◦ special effects for movies,
◦ weather forecasting etc.
very powerful and hence the most expensive.
Mainframe computers
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powerful multi-user computers capable of supporting many hundreds or
thousands of users simultaneously
capable of processing data at very high speeds (hundreds of millions
instructions per second).
large in size, expensive and used to process large amounts of data quickly.
mostly used in banks, airline and railway reservation systems, aircraft design
companies etc.
Mini-computers
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these are multi-user computers capable of supporting up to
hundreds of users simultaneously
were developed with the objective to launch low cost computers.
less hardware features than in mainframes in order to reduce costs.
speed or storage capacity is lower than that of mainframes.
their market has diminished as buyers opt for less expensive but
increasingly powerful personal computers (PCs).
Micro-computers
 developed as a result of the invention of the micro-processor
(single chip CPU) .
 are cheaper than mini-computers .
 they can further be classified into the following categories :
◦ Workstations
◦ PCs
◦ Laptop computers
◦ Palm PCs
Micro-computer category
Description
Workstations
-are powerful, single-user computers.
-these are desktop machines that are mainly used for
graphics-intensive applications such as computer aided
design (CAD) and the simulation of complex systems.
-they use sophisticated display screens featuring high
resolution colour graphics.
Personal computers (PCs)
-small, single-user computers based on a
microprocessor.
-these desktops are also known as ‘home computers’
and are easier to use and more affordable than
workstations.
-most often used for word processing and small
database applications.
Laptop computers
-also called ‘notebook computers’.
-are portable computers that can fit in a briefcase.
-popular with travelers and other mobile users who need
a computer that can go with them.
Palm PCs
-these are handheld computers.
-these devices were phased out in 2000.
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refers to the stored programs.
they are programs that enable a computer to do
something meaningful.
two main types of software: system and application
◦ System software
 consists of general programs written for computers which provide the
environment in which to run application programs.
 these programs interact with hardware at a very basic level.
 system software therefore serves as the interface between hardware and
the user e.g. operating systems, compiler software and utilities.
 Operating system -an integrated set of specialized programs that is
used to manage the overall operations of a computer e.g. Windows
XP,7,8…… Android, Linux etc.
 Utilities – programs that support a computer in terms of specific tasks,
such as file copying, sorting e.g. check disk, disk defragmenter, task
scheduler etc.
 Compiler software – (see next slide)
-Compiler software is another type of system software.
-it translates a source program (user written program) into an
object program (binary form)
-different compilers are available for different programming
languages e.g. Java compiler, C++ compiler etc
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these are programs designed to solve user problems by
accomplishing specific tasks .
Applications can include hotel reservation systems, game
programs, weather forecasting programs etc.
Other specific purpose application software include:
◦ Word processors
 allow you to create, edit, format, store and print text and graphics e.g.
Microsoft Word, Polaris Word and WordPerfect.
◦ Spreadsheets
 allow users to manipulate numbers by doing repetitive numeric
calculations, using formulae and the creation of graphics and charts e.g.
Microsoft Excel and Polaris Sheet
◦ Presentation software
 for making business presentations e.g. Microsoft PowerPoint and Polaris
Slide.
◦ Database management software
 enable users to store, modify and extract information from a database
e.g. Microsoft Access
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is a printed circuit board that houses the
processor, chipset, memory and expansion slots.
type of motherboard influences the system speed
and computer system upgrade options.
aka as ‘system board’ or ‘main board’
motherboard manufacturers include Intel,
Gigabyte, MSI, ASUS, ASROCK and Acer.
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Form factor
◦ ATX and Micro-ATX
◦ Front panel connectors
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Bus architecture
◦ Internal and external buses
◦ System clock and bus speed
◦ Parallel and serial bus types
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More Components
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CPU socket and chipset
Chipset and memory architecture
Northbridge/Southbridge
Memory
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form factor of a motherboard describes its shape,
physical layout and the type of case and power supply
unit (PSU) that can be used.
most motherboards are based on the ATX or Micro-ATX
design.
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ATX and Micro-ATX
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Front panel connectors
◦ developed by Intel in 1995 to provide a new design for PC
motherboards
◦ can be full size or micro(with fewer expansion slots.)
◦ located on the front panel of the chassis and connects to
motherboard.
◦ These include:
 Power button/reset button
 Power light
 Disk drive activity lights: these show when a disk is being
accessed
 Universal serial bus (USB) ports
 Audio ports
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Internal and external buses
◦ An internal (or local) bus
 connects core components, such as the CPU,
memory and system controllers
◦ An external bus (or expansion bus)
 allows for additional components to be connected to
a computer;
 these components could be peripheral (located
outside the case) or adapter cards (located inside
the case)
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System clock and bus speed
◦ system clock synchronizes the operation of all PC parts and
provides the basic timing signal for the CPU.
◦ It consists of a clock generator that sets up a timing signal
and a clock multiplier that produces different timing
signals for different types of bus.
◦ Clock speeds are measured in megahertz (MHz) or
gigahertz (GHz)
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Parallel and serial bus types
◦ The width of a parallel bus (e.g. 32-bit) and the clock speed
determine data transfer rates.
◦ data rate for serial communication is based on the clock
speed and encoding mechanism.
◦ Newer bus designs e.g. USB & Firewire use serial
communication .
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CPU socket and chipset
◦ A chipset is a set of electronic components in an integrated
circuit that manages the data flow between the processor,
memory and peripherals. It is usually found on the
motherboard.
◦ type of chipset on the motherboard can affect the type of
processor, processor speed, type & amount of system
memory, & type(s) of system bus.
◦ chipset consists of a number of controllers that handle the
transfer of data between the CPU and various devices e.g.
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I/O controller
PS2 keyboard and mouse controller
System memory controller
Sound, network, video controllers
Chipset and memory architecture
◦ link between the CPU and system memory is a key factor in
determining system performance.
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Northbridge (host bridge)
◦ is a microchip on some PC motherboards and is connected
directly to the CPU and thus responsible for tasks that require
the highest performance
◦ its main function is system memory controller, connecting the
processor to random access memory (RAM)
◦ also supports other faster components, such as the
accelerated graphics port (AGP) bus.
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Southbridge (I/O Controller Hub )
◦ is not directly connected to the CPU.
◦ designed to control all of the I/O functions not handled by the
Northbridge (often older, slower technologies), such as USB,
serial, parallel, system basic input-output system (BIOS), disk
controllers and onboard audio or network adapters.
◦ the Northbridge ties the Southbridge to the CPU.
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Its mainly in two categories: primary and secondary.
There is also high speed cache memory.
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Features of primary memory :
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It is connected to the processor.
Data stored in it is easily changed.
It holds the data that the processor is actively working with.
It interacts with the processor (millions of times per second).
It needs constant power.
Features of secondary memory:
◦ It is connected to main memory through the bus and a controller.
◦ Data stored in it is easily changed; however, changes are slow
compared with main memory.
◦ It is used for the long-term storage of data.
◦ Before data can be used, it must be copied from secondary
memory into main memory.
◦ Secondary memory does not need power to function.
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Main memory
◦ is sometimes referred to as RAM (random-access memory .)
◦ this is where programs and data are kept when the
processor is actively using them.
◦ When programs and data become active, they are copied
from secondary memory into main memory, where the
processor can interact with them. A copy then remains in
secondary memory.
◦ RAM is volatile; it loses its contents as soon as power is
removed.
◦ RAM normally is dual inline memory modules (DIMMs) fitted
to motherboard sockets.
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Cache Memory
◦ is a very high speed semiconductor memory which
can speed up CPU.
◦ It acts as a buffer between the CPU and main
memory.
◦ It is used to hold those parts of data and programs
which are most frequently used by CPU.
◦ The parts of data and programs are transferred
from disk to cache memory by the operating
system, from where CPU can access them.
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Read-only memory (ROM)
◦ data stored in ROM cannot be modified, or can be
modified only slowly or with difficulty,
◦ it is mainly used to distribute firmware (software
that is very closely tied to specific hardware and
unlikely to need frequent updates).
◦ It is non-volatile storage (that is, storage that
retains its data when power is removed) .
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The Basic Input-Output System (BIOS)
◦ known as system BIOS or ROM BIOS.
◦ aka ‘firmware’ because it consists of both the physical chip
(hardware) and the programs coded into such (software).
◦ is the first software run by a PC when it is powered on.
◦ purposes to initialize and test the system hardware
components and to load an OS.
◦ it provides the following features:
 Power-on self-test (POST) diagnostic tests
 A real-time clock (RTC) that keeps track of the current
date and time
 Setup menus that allow for low-level hardware
configuration
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is where data is kept on a long-term basis.
Most popular storage device is the hard disk
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Primary memory
Fast
Expensive
Low capacity
Secondary memory
Slow
Cheaper
High capacity
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Works directly with processor
Not connected directly to the processor
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1. Define :
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OS
application software
micro-computer
mainframe
bus.
2. Briefly discuss the types of computer
memory and their respective uses.