Transcript Introduction 3

System Software
• “Background software”, manages the
computer’s internal resources
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System Software
• Operating system
– Interface between application software
(and user) and the computer
– Runs programs
– Processes data
– Stores information
– Frees the user from complicated, technical
tasks
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Examples of Microcomputer Operating
System Software
• DOS - original standard for
IBM compatibles
• Windows - a graphical
operating environment
• Windows 95, Windows 98
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Examples of Microcomputer Operating
System Software
• Windows NT - for powerful
workstations & networks
• OS/2 - competitor to Windows 95
• Macintosh Operating System
• Unix - originally for minicomputers,
now used on microcomputers and
Internet servers
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Hardware - devices for
• Input
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Hardware - devices for
• Input
• Processing
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Hardware - devices for
• Input
• Processing
• Storage
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Hardware - devices for
•
•
•
•
Input
Processing
Storage
Output
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Hardware - devices for
•
•
•
•
•
Input
Processing
Storage
Output
Communications
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Input Devices
• Translate data from form that humans
understand to one that the computer
can work with
• Most common are keyboard and mouse
Selector Buttons
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The System Unit
• Electronic
circuitry
within the
computer
cabinet
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The System Unit
• Two general parts
Central Processing
Unit (CPU) - an
integrated microcircuit that
translates data into
information
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The CPU consists of :
Control Unit (CU)
Arithmetic and Logical Unit
(ALU)
Some Registers.
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The Control Unit (CU) within a
CPU coordinates all activities
of the computer by determining
which operations to perform
and in what order to carry them
out. The CU transmits
coordinating control signals to
other computer components.
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The ALU consists of electronic
circuitry to perform arithmetic
operations (addition, subtraction,
multiplication and division),
logical operations (and, or, not, …)
and to make some comparisons
(less-than, equal, … etc.)
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The System Unit
• Two general parts
• Memory - referred to as
primary storage or
random access memory
(RAM), it temporarily
holds data and programs
for use during
processing (volatile)
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RAM
RAM consists of locations or
cells. Each cell has a unique
address which distinguishes
it from other cells.
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ROM: Read Only Memory
ROM is part of memory.
Programmed at
manufacturing time
Its contents cannot be changed
by users
It is a permanent store
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Secondary Storage
• Stores data and programs
permanently: its retained after the
power is turned off
• Located outside the CPU, but most
often contained in the system
cabinet
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Three Kinds of Disk Drives
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Common Secondary Media
• Diskettes
– Data represented as magnetic spots on
removable flexible plastic disks
– Most common size is 3 1/2 inches, in a rigid
plastic case
– Disk drive holds the diskette, reads or
retrieves the data and writes or stores data
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Common Secondary Media
• Hard drive
– Data is represented magnetically as
with diskettes
– Normally more than one rigid platter in
a sealed unit
– These disks are not removable
– Significantly more capacity and faster
operating than diskettes
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Output Devices
Pieces of equipment that translate the
processed information from the CPU
into a form that humans can
understand.
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Output Devices
Monitors
Printers
Dot matrix printers
Ink jet printers
Laser printers
Sound plasters
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Communications Devices
Hardware that sends and receives
data and programs from one
computer or secondary storage
device to another.
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Units of Measurements
•
•
•
•
•
•
Bit (Binary Digit)(takes two values: 1 or 0)
Byte = 8 bits
KB (Kilo-byte) = 1024 bytes
MB (mega-byte) = 1024 KB
GB (giga-byte) = 1024 MB
TB (Tera-byte) = 1024 GB
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Data
Data are details of various types of
transactions and details relating to specific
situations, which are input to a data
processing system (e.g. computer) for
processing in a prescribed way. Examples of
data relating to students are student-number,
student-name and grades.
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Data
• Document files
• Worksheet files
• Database files
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Information
Information: the result of processing data.
 Information:
Must serve a useful purpose
Must be of an acceptable level of accuracy
Must be available at the right time
Must be relevant to the enterprise, person, … etc.
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Knowledge
• Putting a number of information with the
same type or same topic would be a
knowledge.
Connectivity
The computer’s
capability to
send and
receive
information
from other
locations.
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Connectivity
Systems of interconnected
computers, known as networks, are
the sources of distant information.
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Connectivity
Systems of interconnected computers,
known as networks, are the sources of
distant information.
The National
Information
Infrastructure (NII) is
currently the
Internet.
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Computer Viruses
A computer virus is an application
program designed and written to
destroy other programs.
- It has the ability to:
Link itself to other programs
Copy itself (it looks as if it repeats
itself)
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Examples of Viruses
Monkes
ABC
Crabs
CIH

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How do you know if you have
a virus?
• Lack of storage capability
• Decrease in the speed of
executing programs
• Unexpected error messages
• Halting the system
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Protection against Computer Viruses
• Buy original copies of software only
• Make backups of your files
• Do not let any body to insert a diskette in
your computer unless you are sure they do
not have any viruses.
• Write-protect your disks
• Use anti-virus programs