Information and Communications Technology

•What is a computer
•Types of computers
•Components of a computer system
05/31/13 06:19 Information and Communications Technology 2

What is A Computer
 A computer is a general purpose device
which can be programmed to carry out a
finite set of arithmetic or logical
operations. Since a sequence of
operations can be readily changed, the
computer can solve more than one kind
of problem.

What is A Computer
 They use digital circuits and are
designed to operate on two states,
namely bits 0 and 1. They are
analogous to states ON and OFF. Data
on these computers is represented as a
series of 0s and 1s.

Types of Computers
Computers can be generally classified by
size and power as follows, though there is
considerable overlap:
1.Personal computer: A small, single-user
computer based on a microprocessor.
Examples are: Laptop, iPad, iPhone,
Desktop

Types of Computers
2. Workstation: A powerful, single-user
computer. A workstation is like a
personal computer, but it has a more
powerful microprocessor and, in
general, a higher-quality monitor.

Types of Computers
3. Minicomputer: A multi-user computer
capable of supporting up to hundreds of
users simultaneously.
4. Mainframe: A powerful multi-user
computer capable of supporting many
hundreds or thousands of users
simultaneously.

Types of Computers
5. Supercomputer: An extremely fast
computer that can perform hundreds of
millions of instructions per second.

Types of PCs
 Desktops: A desktop is intended to be
used on a single location. The spare
parts of a desktop computer are readily
available at relatively lower costs. Power
consumption is not as critical as that in
laptops. Desktops are widely popular for
daily use in the workplace and
households.

Types of PCs
 Laptops: Similar in operation to
desktops, laptop computers are
miniaturized and optimized for mobile
use. Laptops run on a single battery or
an external adapter that charges the
computer batteries.

Types of PCs
 Laptops are enabled with a built-in
keyboard, touch pad acting as a mouse
and a liquid crystal display. Their
portability and capacity to operate on
battery power have proven to be of great
help to mobile users.

Types of PCs
 Netbooks: They fall in the category of
laptops, but are inexpensive and
relatively smaller in size. They had a
smaller feature set and lesser capacities
in comparison to regular laptops, at the
time they came into the market.

Types of PCs
 Personal Digital Assistants (PDAs): It is
a handheld computer and popularly
known as a palmtop. It has a touch
screen and a memory card for storage
of data. PDAs can also be used as
portable audio players, web browsers
and smartphones.

Types of PCs
 Most of them can access the Internet by
means of Bluetooth or Wi-Fi
communication.

Types of PCs
 Wearable Computers: A record-setting
step in the evolution of computers was
the creation of wearable computers.
These computers can be worn on the
body and are often used in the study of
behavior modeling and human health.

Types of PCs
 Wearable computers do not have to be
turned on and off and remain in
operation without user intervention.

Types of PCs
 Tablet Computers: Tablets are mobile
computers that are very handy to use.
They use the touch screen technology.
Tablets come with an onscreen
keyboard or use a stylus or a digital pen.
Apple's iPad redefined the class of
tablet computers.

Types of PCs
 Tower computers: The term refers to a
computer in which the power supply,
motherboard, and mass storage devices
are stacked on top of each other in a
cabinet. This is in contrast to desktop
models, in which these components are
housed in a more compact box.

Types of PCs
 The main advantage of tower models is
that there are fewer space constraints,
which makes installation of additional
storage devices easier.

•Hardware
•Software
•Peopleware

Hardware
 Personal computer hardware are the
component devices that are the building
blocks of personal computers. These
are typically installed into a computer
case, or attached to it by a cable or
through a port. In the latter case, they
are also referred to as peripherals.

Hardware
1. Monitor
2. Motherboard
3. CPU
4. RAM
5. Expansion
Cards
6. Power Supply
7. Optical Disk Drive
8. Hard Disk Drive
9. Keyboard
10. Mouse

Input vs. Output
 Input is the term denoting either an
entrance or changes which are inserted
into a system and which activate/modify
a process. Example, a trackpad sensing
a finger.
 Output is the term denoting either an
exit or changes which exit a system and
which activate/modify a process.
Example, a screen displaying a photo

Software
 Computer software, or just software, is a
collection of computer programs and
related data that provides the
instructions for telling a computer what
to do and how to do it. Software refers
to one or more computer programs and
data held in the storage of the computer.

Software
 In other words, software is a set
of programs, procedures, algorithms and
its documentation concerned with the
operation of a data processing system.

Software
 When software is stored in hardware
that cannot easily be modified (such as
BIOS ROM in an IBM PC compatible), it
is sometimes called "firmware" to
indicate that it falls into an uncertain
area somewhere between hardware and
software.

Operating System vs.
Application Software
 System software is computer
software designed to operate
the computer hardware to provide basic
functionality and to provide a platform
for running application software.

 System software includes device
drivers, operating
systems, servers, utilities, and window
systems.

 Application Software is a set of
programs that allows the computer to
perform a specific data processing job
for the user. It is a broad category, and
encompasses software of many kinds,
including the internet browser being
used to display a page.

List of Operating Systems
Operating Systems
Unix and BSD UNIX System V, IBM
AIX, HP-
UX, Solaris (SunOS), IRIX
, (too much to list all BSD
OSs)
GNU/Linux (too much to be listed)
Microsoft Windows
Windows 95, Windows
98, Windows
NT, Windows
2000, Windows
Me, Windows
XP, Windows
Vista, Windows 7,
Windows 8
DOS 86-DOS (QDOS), PC-
DOS, MS-DOS, DR-
DOS, FreeDOS

List of Operating Systems
OS
Mac OS Mac OS classic, Mac
OS X
Embedded and real-
time
(too much to be listed)
Experimental Amoeba, Oberon/Blue
bottle, Plan 9 from Bell
Labs

Picture of Windows 8

Picture of Mac OS X

Peopleware
 Peopleware is a term used to refer to
one of the three core aspects of
computer technology, the other two
being hardware and software.

Peopleware
 Peopleware can refer to anything that
has to do with the role of people in the
development or use of computer
software and hardware systems,
including such issues as developer
productivity, teamwork, group dynamics,
the psychology of programming, project
management, organizational factors

Peopleware
 human interface design, and human-
machine-interaction. Example, a
programmer

• Binary code (Base 2)
• Decimal code (Base 10)
• Conversion (Dec. – Binary and vice versa)
• Hexadecimal code (Base 16)

Binary Code
 A binary code is a way of representing
text or computer processor instructions
by the use of the binary number
system's two-binary digits 0 and 1. This
is accomplished by assigning a bit string
to each particular symbol or instruction.

Binary Code
 For example, a binary string of eight
binary digits (bits) can represent any of
256 possible values and can therefore
correspond to a variety of different
symbols, letters or instructions.

Binary Code
 Those methods may be fixed-width or
variable-width. In a fixed-width binary
code, each letter, digit, or other
character, is represented by a bit string
of the same length; that bit string,
interpreted as a binary number, is
usually displayed in code tables in octal,
decimal or hexadecimal notation.

• ASCII
• Binary-coded Decimal

ASCII Code
 The American Standard Code
Information Interchange, or ASCII, uses
a 7 bit binary code to represent text
within a computer, communications
equipment, and other devices that use
text. Each letter or symbol is assigned to
a number from 0 to 127.

ASCII Code
 For example, in the 8-bit ASCII code, a
lowercase "a" is represented by the bit
string 01100001.

Binary-coded Decimal
 Binary-coded decimal, or BCD, is a
binary encoded representation of integer
values that uses a 4-bit nibble to encode
decimal digits.

 Four binary bits can encode up to 16
distinct values; but, in BCD-encoded
numbers, only the first ten values in
each nibble are legal, and encode the
decimal digits zero, through nine.

 The remaining six values are illegal, and
may cause either a machine exception
or unspecified behavior, depending on
the computer implementation of BCD
arithmetic.

Decimal Code
 The decimal numeral system (also
called base ten or occasionally denary)
has ten as its base. It is the numerical
base most widely used by modern
civilizations.

Conversion of Binary to
Decimal
Positional notation method
1.For this example, let's convert the binary
number 110112 to decimal. List the powers
of two from right to left. Start at 20
,
evaluating it as "1". Increment the
exponent by one for each power.

Decimal
1. (cont.) Stop when the amount of
elements in the list is equal to the
amount of digits in the binary number.
The example number, 10011011, has
eight digits, so the list, to eight
elements, would look like this: 128, 64,
32, 16, 8, 4, 2, 1
2. Write first the binary number below the
list.

Decimal
3. Draw lines, starting from the right,
connecting each consecutive digit of
the binary number to the power of two
that is next in the list above it. Begin by
drawing a line from the first digit of the
binary number to the first power of two
in the list above it.

Decimal
3. (cont.)Then, draw a line from the
second digit of the binary number to the
second power of two in the list.
Continue connecting each digit with its
corresponding power of two.

Decimal

Decimal
4. Move through each digit of the binary
number. If the digit is a 1, write its
corresponding power of two below the
line, under the digit. If the digit is a 0,
write a 0 below the line, under the digit.

Decimal
5. Add the numbers written below the line.
The sum should be 155. This is the
decimal equivalent of the binary
number 10011011. Or, written with
base subscripts:15510

Decimal

Decimal
Doubling Method
1.This method does not use powers. As
such, it is simpler for converting large
numbers in your head because you only
need to keep track of a subtotal.
2.Start with the left-most digit of the given
binary number.

Decimal
2. (cont.) For each digit as you move to
the right, double your previous total and
add the current digit. For example, to
convert 10110012 to decimal, we take
the following steps:
3. 1011001 → 0 x 2 + 1 = 1
4. 1011001 → 1 x 2 + 0 = 2
5. 1011001 → 2 x 2 + 1 = 5
6. 1011001 → 5 x 2 + 1 = 11

Decimal
7. 1011001 → 11 x 2 + 0 = 22
8. 1011001 → 22 x 2 + 0 = 44
9. 1011001 → 44 x 2 + 1 = 8910
10. Like the positional notation method, this
method can be modified to convert from
any base to decimal. Doubling is used
because the given number is of base 2.

Decimal
10. (cont.)If the given number is of a
different base, replace the 2 in the
method with the base of the given
number. For example, if the given
number is in base 37, you would
replace the *2 with *37. The final result
will always be in decimal (base 10).

Decimal

Conversion of Decimal to
Binary
Comparison with descending powers of
two and subtraction
1.List the powers of two in a "base 2 table"
from right to left. Start at 20, evaluating it
as "1". Increment the exponent by one for
each power. The list, to ten elements,
would look like this: 512, 256, 128, 64, 32,
16, 8, 4, 2, 1

Binary
2. For this example, let's convert the
decimal number 15610 to binary. What is
the greatest power of two that will fit
into 156? Since 128 fits, write a 1 for
the leftmost binary digit, and subtract
128 from your decimal number, 156.
You now have 28.

Binary
3. Move to the next lower power of two.
Can 64 fit into 28? No, so write a 0 for
the next binary digit to the right.
4. Can 32 fit into 28? No, so write a 0.
5. Can 16 fit into 28? Yes, so write a 1,
and subtract 16 from 28. You now have
12.

Binary
6. Can 8 fit into 12? Yes, so write a 1, and
subtract 8 from 12. You now have 4.
7. Can 4 (power of two) fit into 4 (working
decimal)? Yes, so write a 1, and
subtract 4 from 4. You have 0.

Binary
10. Since there are no more powers of two
in the list, you are done. You should
have 10011100. This is the binary
equivalent of the decimal number 156.
Or, written with base subscripts: 15610 =
100111002

Binary

Binary
Short division by two with remainder
1.For this example, let's convert the
decimal number 15610 to binary. Write the
decimal number as the dividend inside an
upside-down "long division" symbol.

Binary
1. (cont.)Write the base of the destination
system (in our case, "2" for binary) as
the divisor outside the curve of the
division symbol.
2. Write the integer answer (quotient)
under the long division symbol, and
write the remainder (0 or 1) to the right
of the dividend.

Binary
3. Continue downwards, dividing each
new quotient by two and writing the
remainders to the right of each
dividend. Stop when the quotient is 0.
4. Starting with the bottom remainder,
read the sequence of remainders
upwards to the top. You should have
10011100.

Binary
4. (cont.)This is the binary equivalent of
the decimal number 156. Or, written
with base subscripts: 15610 = 100111002.
This method can be modified to convert
from decimal to any base.

Binary
4. (cont.) The divisor is 2 because the
desired destination is base 2. If the
desired destination is a different base,
replace the 2 in the method with the
desired base. For example, if the
desired destination is base 9, replace
the 2 with 9. The final result will then be
in the desired base.

Binary

Hexadecimal Code (optional)
 Hexadecimal (also base 16, or hex) is a
positional numeral system with a radix,
or base, of 16. It uses sixteen distinct
symbols, most often the symbols 0–9 to
represent values zero to nine, and A,B,
C,D,E,F (or alternatively a–f) to
represent values ten to fifteen.

 For example, the hexadecimal number
2AF3 is equal, in decimal, to (2×163) +
(10×162) + (15×161) + (3×160), or
10995.

 Each hexadecimal digit represents four
binary digits (bits), and the primary use
of hexadecimal notation is a human-
friendly representation of binary-coded
values in computing and digital
electronics.

 One hexadecimal digit represents a
nibble, which is half of an octet (8 bits).
For example, byte values can range
from 0 to 255 (decimal), but may be
more conveniently represented as two
hexadecimal digits in the range 00 to
FF.

 Hexadecimal is also commonly used to
represent computer memory addresses.

• Flowchart
• Algorithm

Flowchart
 A flowchart is a type of diagram that
represents an algorithm or process,
showing the steps as boxes of various
kinds, and their order by connecting
these with arrows. This diagrammatic
representation can give a step-by-step
solution to a given problem.

Flowchart
 Process operations are represented in
these boxes, and arrows connecting
them represent flow of control. Data
flows are not typically represented in a
flowchart, in contrast with data flow
diagrams; rather, they are implied by the
sequencing of operations.

Flowchart
 Flowcharts are used in analyzing,
designing, documenting or managing a
process or program in various fields.

Examples of Flowchart

Algorithm
 In mathematics and computer science,
an algorithm is a step-by-step procedure
for calculations. Algorithms are used
for calculation, data processing,
and automated reasoning.

Algorithm
 More precisely, an algorithm is
an effective method expressed as
a finite list of well-defined instructions for
calculating a function.

Algorithm
 Starting from an initial state and initial
input (perhaps empty), the instructions
describe a computation that,
when executed, will proceed through a
finite number of well-defined successive
states, eventually producing
“output” and terminating at a final ending
state.

Algorithm
 The transition from one state to the next
is not necessarily deterministic; some
algorithms, known as randomized
algorithms, incorporate random input.

References
 http://en.wikipedia.org/wiki/Computer#S
oftware
 http://en.wikipedia.org/wiki/Software#Sy
stem_software
 http://en.wikipedia.org/wiki/Personal_co
mputer_hardware
 http://en.wikipedia.org/wiki/Peopleware
 http://en.wikipedia.org/wiki/Input

References
 http://en.wikipedia.org/wiki/Output
 http://www.cs.cmu.edu/~fgandon/lecture
/uk1999/computers_types/
 http://www.buzzle.com/articles/different-
types-of-computers.html
 http://en.wikipedia.org/wiki/Decimal#Non
-uniqueness_of_decimal_representation
 http://en.wikipedia.org/wiki/Binary_code

References
 http://en.wikipedia.org/wiki/Hexadecimal
 http://www.wikihow.com/Convert-from-
Binary-to-Decimal
 http://www.wikihow.com/Convert-from-
Decimal-to-Binary
 http://en.wikipedia.org/wiki/Flowchart
 http://en.wikipedia.org/wiki/Algorithm

References
 http://img.ibtimes.com/www/data/images
/full/2012/02/16/234130-mac-os-x-
mountain-lion-new-features.jpg

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