Transcript Computer system components

MULTIMEDIA
TECHNOLOGY
SMM 3001
COMPUTER TECHNOLOGY
What is a computer?
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Hardware are the devices that make
up the physical components of the
system
Machine that is capable of gathering,
processing, storing and
disseminating data.
A computer must interface with the
world to collect and convert text,
pictures, audio and video into ones
and zeroes.
The data is then stored and
processed within the computer.
Finally, data is converted back into
some human-computer form for
viewing
What is a computer?
Computer :
 A machine that allows user to
store all sort of information/ data
and then ‘process’ that
information/data, or carry out
actions with the information
such as calculating numbers or
organizing words
Computer system
components
User
Hardware
Software
Computer system
Program
Computer system
components
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A computer system is a
combination of hardware and
software. The hardware consists
of the devices of the machine: a
processor that carries out the
detailed instructions defining the
computer's activities, peripherals
that allow our communication
with the machine itself, and
secondary memory.
Computer system
components
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Software directs the operations
of these components. Computer
hardware by itself is capable of
surprisingly few basic
operations, but driven by
application software, the
computer can perform a wide
range of functions.
Computer system
components
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Two basic categories of
software:
System software
 Application software
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Computer system
components
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System software
Consists of the programs that
manage our operation of the
computer.
 Includes operating system and all
the utilities that enable the
computer to function.
 Every general-purpose computer
must have an Operating System in
order to run other programs.
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Computer system components
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Function of OS includes
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coordination of the hardware and
application software
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eg : allow you to start up and shut
down the computer
allocating storage facilities
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eg : save your work as files and
retrieve that work later
Computer system components
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Function of OS includes
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controlling input and output devices
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managing time sharing for linked and
networked computers
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eg : prints documents, scan documents.
eg : allow you to access files from other
computer.
Examples of OS : Windows NT,
DOS, Windows 2000, Windows 98,
OS/2, Unix
Computer system components
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Apllication software
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Consists of the programs that allow
you to work on higher level tasks.
Example : Application for the
following functions :
Word processing
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Advantage of word processing over using
a type writer is that you can make
changes without retyping the entire
document
Easy to manipulate and format document
Spreadsheet
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Used for mathematical calculation such
as accounts, budgets, statistic and etc
Computer system components
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Database application
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Presentation packages
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A collection of related information
that can be manipulated and used to
sort information, conduct statistical
analysis or generate reports
Enable user to create highly stylised
images, chat and graphs for slide
presentations and reports
Communication application
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Software that enable people to send
faxes and email, dial into other
computer and etc.
The Von-Neumann Machine
Model
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John Von Neumann (1940) proposed
a new logical organization or
architecture for the computer.
Machines based on this architecture
came to be called von Neumann
machines.
Von Neumann Machines
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Separated the logical design from the
engineering details.
The description of the components are
based on their function and not merely
the mechanism that achieves that
function
The Von-Neumann Machine
Model
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Von Neumann Machines
(cont..d)
Implement the stored program
concepts
 Employs a binary internal coding
scheme
 Implement sequential instruction
 Two major sub-system : processor
and I/O System
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The Von-Neumann Machine
Model
I/O System
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The input/output system is
usually a collection of devices
including :Keyboard
 Monitor
 Mouse
 Scanner
 Audio devices
 Video devices
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I/O System
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The input/output system has two
main function.
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it serves as a translator in
communications between the user and
the processor.
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Convert data between some analog format,
the internal digital format and then back to
an analog form suitable for the end user
Provides access to secondary memory
devices where both program and data
can be stored when they are not being
used by the processor.
The Processor
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The heart of the computer
Processor consists of two major units: the
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CPU and
Main memory.
The CPU manages the instructionexecution cycle, and main memory is a fast
storage device for holding binary
instructions and data. These are connected
by a signal pathway called a bus. When the
processor is operating, bits are moved
rapidly across this bus. The number of bits
that can be moved simultaneously across
the bus (32 bits for most modern desktop
computers), called the bus width (is an
important factor in determining the speed
of the computer system.
CPU (Central Processing Unit)
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A combination of electronic circuits
that interpret and execute stored
program instructions and
communicate with the rest of a
computer system
Contained in a tiny silicon chip called
a microprocessor
The chip is mounted in a piece of
plastic with metal leads attached to it
Main component
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Arithmetic-logic unit (ALU)
Control unit (CU)
Register
CPU (Central Processing Unit)
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Control Unit – manages the fetching,
decoding and executing of encoded
instruction of store program concepts.
ALU – dedicated to the performance of
the machine’s built-in arithmetic and
logical function.
Register - Special memory unit that
help the CPU keep track of its work:
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Memory address register (MAR)
Memory data register (MDR)
Program Counter (PC)
Instruction Register (IR)
General Register (GR)
Evolution of Microprocessor
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4004 -- introduced in 1971
80286 -- introduced in 1982
Pentium -- introduced in 1993
Pentium II – introduced in 1997
Pentium III Xeon -- introduced in
1999
Itanium – introduced in 2000
Pentium IV –introduced in 2001
Memory
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Memory is usually divided into uniform-size
units that contain a sequence of binary
digits. These sequence of bits are treated
as single units is known as a memory
word, the smallest meaningful unit for
representing information.
A memory word is denoted by a unique
number called its address. Just as your
street address locates your home, a
memory word’s address locates its unique
position in main memory.
Thus, we can conceive of memory as a
collection of standard length, addressable
words. Most processor today use a
memory word size of one byte (one byte =
8 bits)
Bit, byte & binary number
1 Kilobyte (KB) - 1024 bytes
K - Kilo in greek - 1000
For estimates, we can and usually do
think of a kilobyte as 1000 bytes because
1024 is very close to this value.
Example : 64 K = 64 x 1024 = 65,535
byte
MB (Megabyte) = A thousand Kilobyte
(approximately 1 million bytes)
GB (Gigabyte) = 1024 MB (approximately
1 billion (230) bytes)
Summaries
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1 bit - 1 on/off switch
1 byte - 8 bits
1 KB- 1024 byte (210)
1 MB - 1024 KB (1,048,576 byte)
1 GB - 1024 MB (1,073,741,824 byte)
Form of Main Memory
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The two most important forms of
main memory are called:
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Reading a memory item means
consulting its contents.
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RAM (random access memory) –
typically desktop system is
somewhere between 16 and 64
megabyte
ROM (read-only memory) – is more
often in the 4 - 8 megabyte
Original contents remain unchanged
Writing an item means storing
something in its address.
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Original contents are replaced by the
new data
RAM (Random-accessmemory)
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Short-term memory – available only
when the computer is turned on
“Random access” because each memory
word is accessible immediately by its
address
volatile – meaning that they require
constant source of electrical energy to
maintain their contents.
These are called dynamic RAM (DRAM).
Although DRAMs are reasonably fast
and comparatively economical.
This is way it is important to have a
nonvolatile source of secondary memory
that can be used to back up programs
and data.
The CPU & Main Memory
ROM
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Long-term memory – available when the
computer is turned on/off
Also randomly accessible
Is not writeable
Non-volatile
Its contents do not disappear when the
power supply to the computer is shut off.
ROM usually stores proprietary
instruction that the manufacturer has
written for basic system functions such
as starting the computer system, I/O
operations and the like.
REGISTERS
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Registers
 High-speed storage areas used to
temporarily hold small units of
program instructions and data
immediately before, during, and
after execution by the CPU.
 Primary Storage
 Holds program instructions and
data (a.k.a. main memory).
Performance of a system
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The most important factors in
determining the over
performance of the system are:
RAM and transferring rate
 system clock
 bus width
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Stored Program Concept
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Both data and instructions are stored
in a main memory unit. The tasks of
fetching, decoding and executing
the encoded instructions of the
stored program performed by the
control unit are repeated over and
over as long as there are program
instructions to be carried out. This
repeated cycle is called the
instruction execution cycle.
Instruction execution cycle
FETCH
the next instruction
EXECUTE
the instruction
DECODE
the instruction
Managing the InstructionExecution Cycle
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Fetching the instruction
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2.
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The previous cycle has left the address of the
next instruction stored in the program counter
(PC) register. The counter unit now signals for a
copy of that address to be sent to the memory
address register (MAR) over the CPU bus.
The value of the address in the program
counter (PC) is then incremented to reflect the
correct location of the next instruction in main
memory (in preparation for the next cycle).
The instruction, whose address is now stored in
the memory address register (MAR), is now
copied to the memory data register (MDR) over
the data bus. The MDR serves as temporary
storage for such transfers from RAM.
Managing the InstructionExecution Cycle
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Decoding the instruction
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The instruction is next copied over the CPU bus
from the MDR to the instruction register (IR) for
decoding. The IT has special circuits that break
the instruction down into its meaningful
components.
Executing the instruction
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Once the instruction is deciphered in the IR, the
control unit sends the appropriate signals to
commence its execution. This execution is
usually carried out by the arithmetic logic unit
(ALU), which may also employ one or more of
the general registers (GR).
Once execution of the instruction completes,
the CPU returns to step 1 and repeats the
entire process.
Inside the CPU
memory
data
register
memory
address
register
accumulator
(work
register)
instruction
register
program
counter
system
clock
arithmetic
logic unit
FETCH the instruction
1. address of the
next instruction is
transferred from
PC to MAR
2. the instruction is
located in memory
FETCH the instruction
3. instruction is
copied from
memory to MDR
DECODE the instruction
instruction is
transferred to
and decoded in
the IR
EXECUTE the instruction
control unit
sends signals
to appropriate
devices to cause
execution of the
instruction
System Clock
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The entire instruction-execution
cycle is governed by the cadence of
the system clock. Each stage takes a
certain number of clock cycles.
The system uses its clock cycles to
ensure that all its components are
properly sequenced.
Clock cycles are usually measured in
megahertz (MHz), where a
megahertz is one million cycles per
second.
System Clock
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Processor in today’s desktop
computer systems have clock
speeds of 200, 300, 400 MHz
and higher.
A 400-MHz processor has a
clock speed of 400 million
cycles per second.
The single instruction may take
several cycles to complete.
Machine Languages
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Instruction set
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bulit-in set of operations a
particular computer model
Machine language
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A particular set of codes that
implement all the operation in its
instruction set
Instruction set
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There are 3 groups
1.
Data movement operations
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2.
Transfering data from memory to CPU
Transfering data from memory to memory
Performing input and output operations
Arithmetic and logical operations
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+, -, x and / numbers
Comparing two quantities for equality,
greater, lesser and the like
Shifting or rotating bits in quantity
Testing, comparing and converting bits
Instruction set
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Program control operation
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Starting the execution of a
program
Halting the execution of a program
Skipping automatically to other
instruction in the program
Testing a data itemto decide
whether to skip to another
instruction in the program
Moore’s Law
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Moore’s Law
 A hypothesis that states transistor
densities in a single chip will double
every 18 months.
Computer Class
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Supercomputers
Very high-performance
 Specialized computers used
primarily for scientific applications
that require intensive numerical
calculations
 Are used for a variety of tasks
such as meteorological
forecasting, modeling of physical
systems and graphics and image
processing
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Computer Class
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Mainframe
Large sized, powerful multi-user
computer
 Support concurrent programs
 Support up to thousand users at
the same time
 Usage for processing amount of
data quickly (customer bank,
insurance company, airlines)
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Computer Class
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Minicomputer
Smaller and capable of serving a
smaller number of users (dozens
rather than hundreds)
 Eg : small financial system, payroll
system
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Microcomputer
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Personel or single user computers
that were relatively inexpensive