Q:
Chapter no 5. Data Representation
Define Data.
Ans: Data: A computer program is a collection of data, which can be interpreted as
instruction. Data refers to a collection of organized information, usually the results of
experience, observation or experiment, or a set of premises. This may consist of
numbers, words, or images, particularly as measurements or observation of a set of
variables. Or Data is any collection of facts or figures. The data is the raw material
to be processed by a computer. Names of students, marks obtained in the examination,
designation of employees, addresses, pictures, photographs, drawings, charts and
maps can be treated as data.
Q:
What are the types of data?
Ans: Types of Data: The collection of information is called data. Data could of different
types depending upon their use and requirement within the processing concerned.
Mainly, data is divided into two types:
1. Numeric Data
2. Character Data
Numeric Data: The data, which is represented in the form of numbers, is known as
Numeric data. This includes 0-9 digits, a decimal point (.), +/- sign and the letters E”
or “D”. The numeric data is further divided into two groups:
Integer Data: Integer data is in the form of whole numbers. It does not
contain a decimal point; however, it may be a positive or a negative number.
E.g. 2543, -60, 0, +72 etc.
Real Data: Real data is in the form of fractional number. It contains a decimal
point. It can also be positive or negative number. Real data is further divided
into two types:
Fixed pint data: It includes digits (0-9), a decimal point, +/- sign. E.g. 23.07, .11245, +92.786, 17.12 etc,
Floating point data: It is composed of very big or very small numbers,
which cannot be expressed in normal way e.g. it includes time period for
chemical reaction etc. E.g. charge of electron 1.602x10-19 coulomb, Velocity
of light in m/sec 2.9979x108
Character Data: Character data falls into two groups: i) String data, ii) Graphical
data.
String Data: String data consists of the sequence of characters. Characters
may be English alphabets, numbers or space. The string data is further divided
into two type:
Alphabetic Data: The data, which is composed of English alphabets, is
called alphabetic data. For example, names of people, names of places etc.
(Ahmed, AHMED, Karachi, chair etc)
Alphanumeric Data: The data that consists of alphabets as well as
numerals and some special characters is called alphanumeric data. Address,
Employee code, etc are alphanumeric data. For example, 103, Block No.2,
E103, etc
Graphical Data: Pictures, drawing, photographs and maps are considered as
data. Scanner is used to enter this type of data into computer.
20
Sir Sadiq’s computer notes for class IX
Q:
Chapter no 5. Data Representation
Define information.
Ans: Information: Information is a useful, meaningful and organized form of data.
Computer converts data into information after processing. The output or result of
compute is called information. For example: a mark sheet, a utility bill, a printed
cheque, etc.
Input (Data)
Q:
Processing
Output (Information)
Explain Number system?
Ans: Number System: The number system is the system of counting and calculation.
Number system is based on some characters called digits. Each number is made up of
these characters. The number of digits a system uses is called its base or radix. For
example, the number system we use in our daily life is called Decimal system. Its base
is 10(As the name “Deci” implies.) which mean that it uses 10 digits (i.e. 0-9). There
are four types of number systems used in computer operations.
i)
Decimal ii) Binary
iii) Octal
iv) Hexadecimal
Q:
What are type of number system? Explain in details.
Ans: Type of Number System: There are four types of number systems used in
computer operations.
i)
Decimal ii) Binary
iii) Octal
iv) Hexadecimal
Decimal Number System: We use this number system in our daily life for counting
and calculations. This system uses 10 different symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9
which are called Arabic numerals. The decimal number system is also called the base
10 system. Each of the ten digits, 0 to 9, represents a certain quantity.
The value that the digits represent depends on the weight, or position they hold.
The weights are based on the powers of 10 as shown
4th
3rd
103=1000 102=100
2nd
101=10
1st
100=1
Position
Weight
The Binary system: The binary numeral system, or base-2 number system, is a
numeral system that represents numeric values using two symbols, usually 0 (for
OFF) and 1(for ON). The binary system is ideal for internal working of electronic
computer. Computer circuitry represents data in pattern of ON or OFF states of electric
current. The positional weights for the binary system are based on the powers of 2.
The weights for the first four positions are given as under:
4th
23=8
3rd
22=4
2nd
21=2
1st
20=1
For example, 100112 can be represented in decimal as:
100112
= 1 x 24 + 0 x 23 + 0 x 22 + 1 x 21 + 1 x 20
= 1 x 16 + 0 x 8 + 0 x 4 + 1 x 2 + 1 x 1
= 16 + 0 + 0 + 2 + 1
= 19
21
Position
Weight
Sir Sadiq’s computer notes for class IX
Chapter no 5. Data Representation
The Octal System: Octal is a Latin word used for eight (8). Octal has eight
fundamental digits as, 0, 1, 2, 3, 4, 5, 6, 7, so the base of this system is 8. The weights
of digit position are successive powers of 8 as under.
For example 3528 can be represented in decimal as:
3528
= 3 x 82 + 5 x 81 + 2 x 80
= 3 x 64 + 5 x 8 + 2 x 1
= 192 + 40 + 2
= 23410
Hexadecimal: Hexadecimal means 16, therefore this is a base-16 number system. It
has 16 fundamental digits. The first ten digits are same as decimal (0-9) and the rest
of the 6-digtis are the first six letters of English alphabet (A, B, C, D, E, and F). The
letters A through F represents the decimal numbers 10 through 15. This system is often
used in programming as a shortcut to the binary number system. The weights used in
the hexadecimal system are the successive powers of 16. The weights of the first four
digits position are as under:
4th
3rd
163=4096 162=256
2nd
161=16
1st
160=1
Position
Weight
For example, 3AC816 can be represented in decimal as:
3AC816
= 3 x 163 + A x 162 + C x 161 + 8 x 160
Q:
= 3 x 4096 + 10 x 256 + 12 x 16 + 8 x 1
= 12288 + 2560 + 192 + 8
= 1504810
Which number system computer uses for processing of data and why?
Ans: The Binary Number system is used for processing of data. The binary numeral system,
or base-2 number system, is a numeral system that represents numeric values using
two symbols, usually 0 and 1. More specifically, the usual base-2 system is a positional
nation with a radix of 2. Owing to its straightforward implementation in electronic
circuitry, the binary system is used internally by virtually all modern computers.
Q:
What are codes? How many types of “codes” are used in computer system?
Ans: Codes: When number, letters or words are represented by special group of symbols,
they are being encoded and the group of symbols is called “code”. The codes include
Binary codes, Binary-coded-decimal code (BCD), and alphanumeric coded.
Alphanumeric codes include ASCII and EBCDIC.
Q:
What is ASCII code?
Ans: ASCII: The American standard code for information interchange (ASCII) pronounced
as “askee” is a universally accepted alphanumeric code used in most computer and
other electronic equipment. Most computer keyboards are standardized with ASCII.
When we enter a letter, a number, or control command, the corresponding ASCII code
goes into the computer. ASCII has 26 characters and symbols represented by an 8-bit
code series. The first 32 codes in the ASCII table represent the control characters that
are not printed or displayed. The other characters are graphic symbols that can be
printed or displayed.
22
Sir Sadiq’s computer notes for class IX
Q:
Chapter no 5. Data Representation
How a flatting-point number is represented in the computer?
Ans: Floating-point Number: The floating-pint number system, based on scientific
notation, is capable of representing very large and very small numbers without an
increase in the number of bits and also for representing numbers that has both inters
and fractional components.
A floating-point number (also known as real number) consists of two parts plus a
sign. The mantissa is the part of a floating-point numbers that represents the
magnitude of the number. The exponent is the part of a floating-point number that
represents the number of places that the decimal point (or binary point) is to be moved.
A decimal number which is, in integer form, is 254,927,200. The mantissa is .2549272
and the exponent is 9. The mantissa is a fractional number and the exponent is the
power of ten. The floating-point number is written as 0.2549272 x 109.
Q:
How 1’s and 2’s complements are represented in computers?
Ans: Complements: The 1’s and 2’s complements of binary numbers permit the
representation of negative numbers. The 1’s of a binary number is formed by changing
all 1’s to 0’s and 0’s to 1’s. The 2’s complement of a binary number is formed by
adding 1 to the least significant bit of 1’s complement. The left-most bit in a signed
binary number is the sign bit, which tells whether the number is positive or negative.
Finding the 1’s complement of a number:
The 1’s complement of a binary number is formed by changing all1’s to 0’s and 0’s to
1’s.
Binary number
10100110
1’s complement
01011001
Finding the 2’s complement of a number:
The 2’s complement of a binary number is formed by adding 1 to the LSB (Least
Significant Bit) of 1’s complement.
2’s complement = (1’s complement) + 1
Example: Find the 2’s complement of 10010111
Binary number
1’s complement
Add 1
2’s complement
10010111
01101000
+
1
01101001
Book Exercises
Q:
Convert the decimal number into Binary?
23
Sir Sadiq’s computer notes for class IX
Chapter no 5. Data Representation
81410=
2
814
2
407
0
2
203
1
2
101
1
2
50
1
2
25
0
2
12
1
2
6
0
2
3
0
2
1
1
81410= (1100101110)2
Q:
Convert the binary number into decimal?
(1100101110)2=
Q:
1x29+1x28+0x27+0x26+1x25+ 0x24+1x23+1x22+1x21+0x20
1x512+1x256+0x128+0x64+1x32+0x16+1x8+1x4+1x2+0x1
512 + 256 + 0 + 0 + 32 + 0 + 8 + 4 + 2 + 0
814
(1100101110)2 = (814)10
Convert the decimal number into equivalent octal number?
75010=
Q:
8
8
8
8
750
93
11
1
6
5
3
75010= (1356)8
Convert the octal number into decimal number?
6558=
Q:
6 x 82 + 5 x 81 + 5 x 80
6 x 64 + 5 x 8 + 5 x 1
384 + 40 + 5
429
6558 = 42910
Convert the decimal number into hexadecimal number?
178010=
178010= (6F4)16
Q:
16
16
16
1780
111
6
4
F
Convert the hexadecimal number into decimal?
(A109)16= A x 163 + 1 x 162 + 0 x 161 + 9 x 160
10 x 4096 + 1 x 256 + 0 x 16 + 9 x 1
40960 + 256 + 0 + 9
41225
(A109)16= (41225)10
24
(15=F)
Sir Sadiq’s computer notes for class IX
Q:
Chapter no 5. Data Representation
Convert the hexadecimal number into binary number & Binary number into
hexadecimal?
Table of Conversion between Binary and Hexadecimal
Q:
Hexadecimal
Binary
Hexadecimal to binary
0
0000
(A35)16=
1
0001
A
3
5
2
0010
1010 0011 0101
3
0011
Ans: 1010001101012
4
0100
5
0101
Binary to hexadecimal
6
0110
(1110100)2=
7
0111
01111
0100
8
1000
7
4
9
1001
Ans: 7416
A
1010
B
1011
C
1100
D
1101
E
1110
F
1111
Convert the Octal number into binary number & Binary number into octal?
Table of Conversion between Binary and Hexadecimal
Octal
0
1
2
3
4
5
6
7
Binary
000
001
010
011
100
101
110
111
Octal to binary
(453)8=
4
5
3
100 101 011
Ans: 1001010112
Binary to octal
(1110100)2=
001 110
1
6
Ans: 1648
100
4
Q:
Convert the octal numbers into hexadecimal?
117
Ans: Convert first into binary then into hexadecimal by yourself.
Q:
Convert the hexadecimal numbers into octal number?
44CD
Ans: Convert first into binary then into octal by yourself.
Sir Sadiq’s Computer Notes for Class IX.
Composed by: Sir Sadiq, smsadiqnoori@gmail.com
25
Sir Sadiq’s computer notes for class IX
Q:
Chapter no 6. Boolean Algebra
What is Boolean algebra?
Ans: Boolean algebra: Boolean algebra was named after George Boole, who first
defined an algebraic system of logic in the mid-19th century. Boolean algebra is a
convenient and systematic way of expressing and analyzing the operations of logic
circuits. It is a mathematical system for formulating logical statements with symbols.
It is applied in the design and analysis of digital systems. It provides the operations
and the rules for working with the set {0,1}. Electronic and optical switches can be
studied using this set and the rules of Boolean algebra. Boolean algebra is now being
used extensively in designing the circuits used in computers.
Q:
What are the Rules of Boolean algebra used to simplify an expression?
Ans: Rules of Boolean algebra:
Rule
Rule
Rule
Rule
Rule
Rule
Rule
Q:
1:
3:
5:
7:
9:
11:
12:
A+0 =A
Rule
A.0 =0
Rule
A+A =A
Rule
A+A=1
Rule
A
=A
Rule
A+A.B = A + B
(A+B) (A+C) = A+BC
2:
4:
6:
8:
10:
A+1 =
A.1 =
A.A =
A. A =
A+A.B =
1
A
A
0
A
Define Boolean constants and variable.
Ans: Boolean Constant: Boolean algebra used binary values 0 and 1 as Boolean
constant.
Variable: The variables used in the Boolean algebra are represented by letter such
as A,B,C, x,y,z, etc, with each variable having one of two and only two distinct
possible values 0 and 1.
Q:
Define Truth table.
Ans: Truth Table: The truth table is a systematic listing of the values for the dependent
variable in terms of all the possible values of independent variable. It can also be
defined as a table representing the condition of input and output circuit involving two
or more variables. In a binary system, there is 2n number of combinations, where n is
the number of variables being used. A truth table is a table of all possible
combinations of the variables.
Q:
How many basic logical operators used in Boolean algebra?
Ans: Logical Operator: There are three basic logical operations used in Boolean algebra.
1. ÖR” Operator is represented by a “+” sign. It is used for logical addition or
Boolean Sum.
2. ÄND” Operator is represented by a “.”. It is used for logical multiplication.
3. “NOT” Operator is represented by a prime (‘) or bar (-) on the variable. It is
used for complement operation.
26
Sir Sadiq’s computer notes for class IX
Q:
Chapter no 6. Boolean Algebra
Define OR operator.
Ans: OR Operator: OR operator is represented by a “+” sign. It is used for logical
addition or Boolean Sum. The “+” symbol or OR operation is used by listing all
possible combinations of, for example, A and B and the resulting value of C in the
equation
A + b = C. It is read as “A OR B is equal to C”.
It may be noted that as there are two variables A and B so only 4 (2 n = 22)
combinations of inputs are possible as shown in the Truth Table.
INPUTS
OUTPUT
A
B
A+B=C
0
0
0
0
1
1
1
0
1
1
1
1
Q:
Define AND operator.
Ans: AND Operator: This operation is represented by dot “.” or the absence of an
operator. It is used for logical multiplication. The AND operation is defined by listing
all possible combinations of, for example, A and B and the resulting valued of C in
the equation
A . B = C or AB = C read as Ä AND B is equal to C”.
The truth table for logical AND operation is shown in the table.
INPUTS
A
0
0
1
1
B
0
1
0
1
OUTPUT
A.B=C
0
0
0
1
Q: Define NOT operator.
Ans: NOT Operator: This operation is represented by a prime (‘) or bar (-) on the
variable. It is used for complement operation. For example, A (read as A bar) means
complement of A or NOT A.
INPUTS
A
0
1
Q: What are the Laws of Boolean algebra?
OUTPUT
A
1
0
Ans: Laws of Boolean algebra: There are three basic laws of Boolean algebra are the
same as in ordinary algebra.
1) Commutative Laws 2) Associative Laws 3) Distributive Laws
27
Sir Sadiq’s computer notes for class IX
Chapter no 6. Boolean Algebra
Q:
Commutative Laws:
i.
The Commutative law of Addition for two variables is written as. A + B = B
+ A. The Law states that the order in which the variables are ORed (added)
makes no difference. Remember that in Boolean algebra addition and OR
operation are same.
ii. The commutative law of multiplication for two variables is written as A . B
= B. A. This law states that the order in which the variables are ANDed
(multiplied) makes no difference.
Associative Laws:
i.
The Associative law of addition is written as follows for three variables. A +
(B + C) = (A + B ) + C. This law
states that when ORing more than two variables, the result is the same
regardless of the grouping of the variables.
ii. The Associative Law of multiplication is written as follows for three
variables. A(BC) = (AB)C. This law states that it makes no difference in
what order the variables are grouped when ANDing more than two
variables.
Distributive Law:
i.
The distributive law is written for three variables as follows. A(B + C) = AB
+ AC. This law states that ORing two or more variables and then. Anding
the result with a single variable is equivalent to ANDing the single variable
with each of the two or more variables and then ORing the products. The
distributive law also expresses the process of factoring in which the
common variable A is factored out of the product terms.
AB + AC = A(B + C)
What are the Standard forms of Boolean Expressions?
Ans: Standard form of Boolean Expression: All Boolean expressions regardless of
their form can be converted into either of two standard forms.
1.
2.
The Sum-of-Product (SOP)
The Product-of-Sum (POS)
The Sum-of-Product (SOP):
When two or more products terms are summed by Boolean addition, the resulting
expression is a sum-of-product (SOP).
Examples:
A + ABC
ABC + CDE + BCD
AB + ABC + AC
An algebraic expression can be changed into SOP by applying Boolean algebraic
techniques. For example, the expression A(B + CD) can be converted to SOP
form by applying the distributive law:
28
Sir Sadiq’s computer notes for class IX
Chapter no 6. Boolean Algebra
A(B + CD) = AB + ACD
Example:
Convert the following expression to SOP form?
(A + B)(B + C + D)
Solution:
(A + B) (B + C + D) = AB + AC + AD + BB + BC + BD
The Product-of-Sums (POS):
When two or more sum terms are multiplied, the resulting expression is a productof-sums (POS).
Examples:
(A + B) (A + B + C)
(A + B + C) (C + D + E) (B + C + D)
(A + B) (A + B + C) (A + C)
Q:
What is Karnaugh Map? How can Karnaugh Map help in simplifying a
Boolean expression?
Ans: Karnaugh Map: Karnaugh map provides a systematic method for simplifying
Boolean expression and if properly used will produced the simplest SOP or POS
expression possible. The Karnaugh map is also known as K-map. It is similar to a
truth table because it presents all of the possible values of input variables and the
resulting output for each value. K-map is an array of cells in which each cell
represents a binary value of the input variables. Karnaugh maps can be used for
expressions with two, three, four and five variables.
K-maps, are often used to simplify logic problems with 2, 3 or 4 variables. 2-variable
Karnaugh maps are trivial but can be used to introduce the methods need to learn.
A
The map for a 2-input OR gate looks like this.
0
B
A
0
Output
Input
B
1
1
1
1
1
A+B
The values of one variable appear across the top of the map, defining the column
values, while the values of the other variable appear at the side, defining the values
of the variable in each row.
Q:
State the Prove Demorgan’s theorem.
Ans: Demorgan’s theorem: The most important logic theorem for digital electronics,
this theorem says that any logical binary expression remains unchanged if we
1.
2.
3.
4.
Change all variables to their complements
Change all AND operations to Ors.
Change all OR operations to ANDs.
Take the complement of the entire expression.
29
Sir Sadiq’s computer notes for class IX
Chapter no 6. Boolean Algebra
DeMorgan, a mathematician who knew Boole, proposed two theorems that are an
important part of Boolean Algebra. They help in simplifying complicated logical
expression.
i)
XY = X + Y
The complement of a product of variable is equal to the sum of the compliments of
the variables.
Proof:
The theorem can be proved by the Truth table:
X
0
0
1
1
Y
0
1
0
1
X.Y
0
0
0
1
X.Y
1
1
1
0
X
1
1
0
0
Y
1
0
1
0
X+Y
1
1
1
0
12
ii)
X + Y = X.Y
The complement of a sum of variables is equal to the product of the complements
of the variables.
Proof:
The theorem can be proved by the Truth table:
X
0
0
1
1
Y
0
1
0
1
X+Y
0
1
1
1
X+Y
1
0
0
0
X
1
1
0
0
Y
1
0
1
0
X.Y
1
0
0
0
Sir Sadiq’s Computer Notes for Class IX.
Composed by: Sir Sadiq smsadiqnoori@gmail.com
30
Sir Sadiq’s computer notes for class IX
Chapter no 7. Computer software
Q: What is software?
Ans:
Software: Software is a general term used for computer
programs. A computer program is a planned, step by step set of
instructions that directs the computer what to do and how to do. OR
computer software is a general term used to describe a collection of
computer programs, procedures and documentation that perform some
task on a computer system. There are two types of software, namely,
System Software and Application software.
Q: Define system software and application software in detail.
System Software: The users interact with the application software
whereas system software enables the application software to interact
with the computer hardware. System software is “background”
software. It includes programs that help the computer manage its
internal resources. System software are of following types:
1. Operating system: An operating system is a set of programs
which starts a computer and allows the users to interact with the
hardware and software present in the computer. Without operating
system, a computer cannot do anything useful. Some of the
popular operating systems used in personal computer are: DOS,
Windows, UNIX, Linux, Solaris, etc.
2. Language Translator: It translates a computer program into
machine understandable form. Language translators are
Interpreter, Compiler and Assembler. Interpreter translates
and executes each program statement one at a time, translation is
required if program is run again. Compiler translates the whole
program at a time and stores translated program on disk. The
Assembler is translator for Assembly language.
3. Data-management software: Data-management software
includes database and file management programs that manage
data for an operating system. They can organize, update and print
data.
4. Editors: Editors allow the user to type-in a program generate text
and make modifications whenever necessary. A program is first
written in an editor and then is compiled.
5. Utility software: These are program that users can purchase as
separate products to perform a wide range of functions. The
programs for these functions are PC-Tools, Scand Disk, Norton Disk
Driver, Antivirus, etc.
30
Sir Sadiq’s computer notes for class IX
Chapter no 7. Computer software
Application software: Application software is programs that help a
user perform a specific job. It enables the computer to produce useful
work such as writing a letter, making a reports and preparing
accounts etc. Application software is further divided into two classes.
1. General purpose application software
2. Special purpose application software
General purpose application software: These are called
packaged software or commercial software. Single software can be
applied to a wide variety of tasks. It includes, M.S Office, Corel Draw,
Inpage, Adobe Photoshop, etc.
Special purpose application software: The software that is
designed to perform a specific task is known as special purpose
application software. This is also called Custom Software. The
software can perform only one task for which it has been designed.
For example, Software to process inventory control, software to
maintain Bank Accounts, software used in Airline Booking System.
Q: Write a note on Disk Operating System (DOS).
What are the types of DOS commands?
Ans:
DOS: DOS is an operating system. It manages the routine work of
computer system, controlling everything from internal memory, monitor
display, keyboard input and external communication. It was developed
by a US company called Microsoft in 1981. It provides us with two types
of commands namely, internal and external commands.
Internal commands: Internal commands are built into DOS, and
loaded with DOS. These commands are immediately available in memory
and con not be seen in the disk files list. The internal commands are
DIR, CLAS, DATE, TIME, COPY, VER, VOL, DEL, TYPE, REN, PROPMT,
MD, RD, CD, and PATH etc.
External Commands: External commands are stored on disk as files.
Some commands are FORMAT, CHKDSK, LABEL, DISKCOPY, PRINT, SYS,
EDIT, XCOPY, DELTREE, and DOSKEY.
Q: What is an operating system?
Ans:
Operating System: An operating system is a set of programs
which starts a computer and allows the users to interact with the
hardware and software present in the computer. Without operating
system, a computer cannot do anything useful. Some of the popular
operating systems used in personal computer are: DOS, Windows, UNIX,
Linux, Solaris, etc.
31
Sir Sadiq’s computer notes for class IX
Chapter no 7. Computer software
Q: What are wildcard characters? Why they are used?
Ans: Wildcard characters: While looking for a particular file (using DIR
command to see the directory or DEL command to delete files or COPY
command to copy files), you can use two special characters called
wildcards. A question mark (?) can take the place of any single character
and an asterisk (*) can replace any group of characters, even the entire
filename or extension. They can be used when searching/deleting/ or
copies files on a disk.
For example:
TEST?
Includes TEST, TEST1, TEST2, TESTS, but
not the TESTS1 (it has an extra character)
*.EXE
It refers to all files with .EXE extension.
*.*
Includes all files on the default drive.
Q: What is a Directory? What DOS commands are used to create,
change and delete a directory?
Ans: Directory: A directory contains information about each file such as its
name, size in bytes and the date and time they were created or last
updated. The main directory, called the root directory, can contain many
sub-directories and these subdirectories can contain other subdirectories.
The root directory is not referred to by name. Instead, it is always
indicated by a backslash (\). If you are working in a subdirectory called
IMAGES, the prompt will be:
D:\IMAGES>
We use:
MD or MKDIR command
To create directory
CD or CHDIR command
To change directory
RD or RMDIR command
To remove directory
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Sir Sadiq’s computer notes for class IX
Chapter no 7. Computer software
Write full name of the following:
C.P.U
=
Central Processing Unit
C.U
=
Control Unit
M.U
=
Memory Unit
A.L.U
=
Arithmetic Logic Unit
RAM
=
Random Access Memory
ROM
=
Read Only Memory
L.C.D
=
Liquid Crystal Display
C.R.T
=
Cathode Ray Tube
C.D
=
Compact Disk
GUI
=
Graphical User Interface
BCD
=
Binary Coded Decimal
EBCDIC
=
Extended Binary Coded Decimal Interchange Code
ASCII
=
American Standard Code for Information Interchange
DOS
=
Disk Operating System
DIR
=
Directory
BASIC
=
Beginner’s All-purpose Symbolic Instruction Code
COBOL
=
Common Business Oriented language
ATM
=
Automatic Teller Machine
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Sir Sadiq’s computer notes for class IX
Q:
Chapter no 8. Introduction to windows operating system
What is Windows or windows operating system?
Ans: Windows: Windows is an operating system that helps in operating the computer. It
also manages the hardware and the software present in the computer. We cannot
use the computer without an operating system. Many operating systems are available
but windows is the most popular in personal computers because it is very simple and
easy to learn and use. It helps us to work on the computer. It shows us the
programs, files and folders and allows us to use them. It is a Graphical User Interface
(GUI) based operating system. In DOS we have type-in command, but in windows
command are located on the screen in the form of icons. There are different versions
and flavors of windows, e.g. Windows 2000, Windows XP, Windows NT, Windows
2007, and Windows 8 etc.
Q:
Define what is Desktop? What are its elements?
Ans: Desktop: Windows “Desktop” is like a working surface of a desk. Desktop is where
our applications, folders and shortcuts are located. Desktop contains the following
items:
* Icons
* Task Bar * Start Menu
ICON: An icon is a small colorful graphical picture that
represents an object like a file, folder, program or any
hardware component of the computer. Every icon has a label,
which identifies it. The labels can be changed.
Icons of the Desktop: My Documents, My Computer, My
Network Places, Recycle Bin, Internet Explorer etc.
Task Bar: The Taskbar is a horizontal bar located at the bottom of Windows
Desktop. It contains the Start Button on its left corner and a clock at its right corner.
It between, it displays the buttons for the currently running programs. When we start
a program or a window is opened, a button representing its window appears on the
Taskbar.
When we close the program or window, the button disappears.
Start Button: Start button is present on the left corner of the
Taskbar. It is used to open various links required to use the
computer. On clicking the Start Button, a menu of various items
pops up on the screen. This menu is called the Start Menu. It
shows all the links required to use and maintain the computer.
We can shutdown, restart and / or standby the computer using
the Star button.
Q: Explain the function of windows explorer.
Ans: Windows Explorer: Windows explorer provides another way
to view the contents of the disks and its folders in a tree like
structure. We can navigate between files and folders though
explorer. Files, folders and programs can be opened, moved
and deleted through it. Explorer window has tow panes. Left
pane displays disk drives and folders with + and – sign before
them. Right pane displays the contents of the selected item
from the left pane.
33
Sir Sadiq’s computer notes for class IX
Q:
Chapter no 8. Introduction to windows operating system
Write short notes on the following.
Icon
Taskbar
Recycle Bin
My Computer
My Documents
Windows
Ans: Icon: An icon is a small colorful graphical picture that represents an object like
a file, folder, program or any hardware component of the
computer. Every icon has a label, which identifies it. The labels can
be changed.
Icons of the Desktop: My Documents, My Computer, My
Network Places, Recycle Bin, Internet Explorer etc.
Taskbar: The Taskbar is a horizontal bar located at the bottom of
Windows Desktop. It contains the Start Button on its left corner
and a clock at its right corner. It between, it displays the buttons
for the currently running programs. When we start a program or a window is opened,
a button representing its window appears on the Taskbar.
When we close the program or window, the button disappears.
Recycle Bin: Recycle Bin makes it easy to delete and
undelete
files
and folders. When a file or folder is deleted from any
location,
windows stores it in the Recycle Bin. If a file is deleted
accidentally, we
can move it back from the Recycle Bin. We can also empty recycle bin to save disk
space. We can delete a file or folder by select them and press delete key. We can
also use right mouse button menu to delete files or folders.
My Computer: My computer lets us browse the contents of our computer. The
common tasks that we can perform through my computer are:
1. Access information stored as different storage devices connected with the
computer, such as hard disk, floppy disk, CD / DVD ROM or USB.
2. Create, move, copy, delete or rename files, folders and programs from one
disk to another disk.
3. Execute or run programs from the disks.
4. Configure devices of the computer.
5. Add or remove a printer
My Document: It is a desktop folder that provides a convenient place to store
documents, graphics or other files that we want to access quickly. On the desktop it
is represented by a folder with a sheet of paper in it. When we save a file in a
program such as word pad or paint, the file is by default saved in my documents
unless we choose a different location. OR My Documents is the name of a special
folder on the computer’s hard drive that is commonly used to store a user’s
documents, music, pictures, downloads, and other files.
Windows: It is a rectangular area of Screen that displays different
information. In windows every folder or application has a windows. Following are the
properties of a windows.
1. Every window has a title bar which displays the name of the widow.
2. Windows can be resized,
minimized and maximized by
pressing the buttons at the top
right corner, of the title bar.
3. A window can be closed by pressing the X button at the right of the title
bar.
34
Sir Sadiq’s computer notes for class IX
Q:
Chapter no 8. Introduction to windows operating system
4. A window can be moved at any location of the screen.
How can you change wallpaper of the Desktop?
Ans: Changing
of
Wallpaper:
Wallpaper of the desktop
change by following steps:
1. Close or minimize all
open window
2. Click the right button on
any blank space of the
desktop
3. A menu will appear click
on properties
4. Display property dialog box will appear
5. Click on the background tab
6. Select from the list of currently available wallpapers
7. Click on the “apply” button
8. Click on the “Ok” button
9. Wallpaper has been changed
Q: What is computer Virus?
Ans: Computer Virus: A computer virus is a hidden program, which can infect other
programs by modifying them and causes data loss. It attaches itself to other
programs and executes secretly every time the host program is executed. The virus
replicates itself within a computer system. Some viruses hidden in the computer can
infect the computer at a particular time called Time Bomb viruses. Computer viruses
may perform the following malicious functions.
1. It infects other programs
2. It destroys the data on disk.
3. It spreads from one disk to another.
4. Sometimes it makes the computer unusable.
5. It increases the file size and replicates itself, thus making the wastage of
memory space.
Some names of Viruses: There are a large number of viruses present in the
computer world. These viruses include Brain (developed by a group of Pakistanis),
Joshi, Jerusalem, Friday 13th, Chernobyl, etc.
Q: What is Antivirus?
Ans: Antivirus: Antivirus is another software that when executed removes the virus
programs from the disk. Antivirus software has been developed to get rid of the
computer viruses that can destroy the valuable data and causes the computer to
malfunction. Some of the antivirus programs available are:
* Norton Anti-Virus
* MacAfee * Avast
* PC clean
* AVG
* Panda
Q: How can you create a folder?
Ans: Creating a folder:
1. In My computer or windows explorer, select the drive where you want to
create the new folder.
2. In the File menu, click on the New and then click on Folder
3. The new folder appears with the temporary name.
4. Type a suitable name for the new folder and press the enter key.
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