Punjab School Education Board
Subject:- Computer Science
Class: 11th
Lesson: 1 Number System
Exercise
A. Multiple Choice Questions:
1. Which of the following numbers is the smallest in the
hexadecimal system?
a) 0 b)
1 c) A d) F
2. What is the binary number of the decimal number 15?
a) 0111 b)
1111 c) 0101 d) 0011
3. Which number system is most widely used in everyday
mathematics?
a) Binary b)
Decimal c) Hexadecimal d) Octal
4. What is the base/radix of the hexadecimal number
system?
a) 2 b) 5 c) 8 d)
16
5. (38CB)16, which number system is an example of?
a) Binary b)
Decimal c) Hexadecimal
d) Octal
a. Select True or False from the following:
1. The binary number 1111 represents the decimal number 15. True
✔️
2. The hexadecimal system uses 2 as its base/radix. False
❌
3. The word octal comes from the Latin word Oct which means
8. True ✔️
4. The binary number system can represent any number using
only the digits 0 and 1. True ✔️
5. The digit '9' is a valid digit in the octal number
system. False ❌
6. In the hexadecimal system, the letter 'B' represents 12
in the decimal number system. False ❌
7. The Roman numeral system is an example of a positional
number system. False ❌
c. Short Answer Questions:
Question:1. What is a number system? Write the names of
the basic categories of number systems?
Answer: A number system is a way in which numbers are
represented. It uses different digits that help in calculations and management
of numbers.
Basic categories of number systems:
1. Binary System – Base 2
2. Decimal System – Base 10
3. Hexadecimal System – Base 16
4. Octal System – Base 8
Question:2. Explain decimal number system?
Answer: Decimal Number System:- Decimal number system
is a positional number system whose base is 10. The digits from 0 to 9 are used
in this system. It is the most widely used number system, which we recognize as
numbers in daily life.
Example:
3 2 1 0
👇👇👇
1 2 3 4
It can be written as 1 × 10³ + 2 × 10² + 3 × 10¹ + 4 × 10⁰ in decimal system.
Key Features:
• Base 10
• 10 digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
• Positional system – The position of each digit
affects its value.
Question:3. What is binary number system? Who is the
inventor of this number system?
Answer: Binary Number System:- Binary number system
is a positional number system whose base is 2. Only two digits 0 and 1 are used
in this system. Binary system is also called digital system, as it is used for
information communication and storage in computers and digital circuits.
Example: 1011 (Binary Number)
This is equivalent to 11 in decimal, and can be written as 1
× 2³ + 0 × 2² + 1 × 2¹ + 1 × 2⁰.
Inventor: The binary number system was invented by
Gottfried Wilhelm Leibniz. He described the properties of this system in 1679
and used this number system to establish the basic concepts of mathematics and
logic.
Question:4. Explain the octal number system?
Answer: Octal Number System:- The octal number system
is a positional number system whose base is 8. The digits from 0 to 7 are used
in this system. Octal number system is used to convert from binary easily
because 3 binary bits (digits) can be converted into one octal digit.
Example: 27 (octal number)
This is equivalent to 2 × 8¹ + 7 × 8⁰ = 16 + 7 = 23 in
decimal.
Key features:
• Base 8
• 8 digits (0, 1, 2, 3, 4, 5, 6, 7)
• Positional system – The position of each digit
affects its value.
• Connection between binary and octal – It is very
easy to convert binary to octal, because 3 binary bits make up one octal digit.
Question:5. What is hexadecimal number system?
Answer: Hexadecimal Number System:- The hexadecimal
number system is a positional number system with base 16. This system consists
of 16 digits:
The numbers 0 to 9 and the letters A to F, where A = 10, B =
11, C = 12, D = 13, E = 14, and F = 15.
The hexadecimal number system is widely used, especially in
computer science and digital electronics, because it is related to the binary
system and represents binary numbers in a short and easy way.
Example: 1A3 (hexadecimal number)
This is equivalent to 1 × 16² + A × 16¹ + 3 × 16⁰ = 1 × 256
+ 10 × 16 + 3 × 1 = 256 + 160 + 3 = 419 in decimal.
Key Features:
• Base 16
• 16 digits (0-9 and A-F)
• Positional system – The position of each digit
affects its value.
• Relationship between binary and hexadecimal – A
hexadecimal digit can be represented by 4 binary bits.
Q. Complete the number system conversion:
1. (25)₁₀ = ( )₂ = ( )₈ = ( )₁₆
Answer: (25)₁₀ = (11001)₂ = (31)₈ = (19)₁₆
2. (10111)₂ = ( )₁₀ = ( )₈ = ( )₁₆
Answer: (10111)₂ = (23)₁₀ = (27)₈ = (17)₁₆
3. (47)₈ = ( )₁₀ = ( )₂ = ( )₁₆
Answer: (47)₈ = (39)₁₀ = (100111)₂ = (27)₁₆
4. (A4)₁₆ = ( )₁₀ = ( )₂ = ( )₈
Answer: (A4)₁₆ = (164)₁₀ = (10100100)₂ = (244)₈
Lesson : 2 Introduction to Python
Exercise
A. Multiple Choice Questions.
1. ____ is a default editor that comes with Python.
A. IDLE B.
IPLE C. Text Editor D. Notepad
2. ____ is the shell prompt where we type our commands.
A. << B.
>> C.
>>> D.
<<<
3. The full name of IDE is _______
A. Integrated Direct Environment B.
Integrated Development Environment
C. Information Development Environment D. None of these
4. To run script file code in Python, we can use_________
shortcut keys.
A. FI B.
F2 C. F5 D. F7
5. _____ are like words and punctuation marks in English
language.
A. Literals B.
Identifiers C. Variables D. Tokens
6. ____ are names given to program elements (such as:
variables, functions, lists, tuples, etc.) to identify them.
A. Literals B.
Identifiers C. Variables D. Tokens
7. Literals are _____ values used in source code.
A. Constants B.
Boolean C. String D. Float
8. They are identifiers that are used to store values and we can also change their
value during run time.
A. Constants B.
Variables C. Lists D. Tokens
9. A comment is basically a text that describes the
program code.
A. Execution B.
Compilation C.
Explanation D.
About the above
10. We can display program data on the console in Python
with the _____ function.
A. input() B.
print() C.
output() D. show()
B. Short Answer Questions:
Question:1. What do you know about Python?
Answer: Python is a high-level programming language that is
simple and easy to read. It is interpreter-based and supports object-oriented
programming. Python has many built-in libraries that are used in areas such as
web development, data science, and machine learning. Its wide use and simple
syntax make it ideal for learning a new language.
Question:2. What is an IDE?
Answer: An IDE (Integrated Development Environment) is a
software that provides convenience for programming. It includes a source code
editor, compiler/interpreter, debugger, and build tools. The main purpose of an
IDE is to make the process of writing, testing, and debugging code simple and
fast. Some popular IDEs are PyCharm, Eclipse and Visual Studio.
Question:3. How can you view the list of keywords using
Python cell? Write some examples of keywords.
Answer: You can view the list of keywords using the keyword
module in Python cell. For this, import keyword and print(keyword.kwlist)
command are used. Python keywords like if, else, while, def, class, and True
are used in a special way and have special meaning in Python language.
Some examples: If, else, while, for, def, class, try,
return, import, True, False, None
Question:4. How will you declare variables in Python?
Give examples.
Answer: In Python, no special keyword is required to declare
variables, you just give the variable a name and assign it a value.
Examples:
x = 10 #
Integer type variable
name = "John" #
String type variable
is_active = True #
Boolean type variable
height = 5.9 #
Float type variable
Here, x is assigned to 10, name to "John",
is_active to True, and height to 5.9. Variables in Python can be used in this
way wherever needed.
Question:5. Why is the print() function used in Python
programs?
Answer: The print() function is used in Python programs to
display data on the console or screen. Its main purpose is to show the result
of any input or calculation to the user.
Example:
name = "John"
print("Hello, " + name) # Output: Hello, John
Here, the print() function displays "Hello, John"
on the console. With this, the developer or user can easily see the result of
the code.
C. Long Answer Questions:
Question:1. Define tokens? Describe the different tokens
used in Python.
Answer: Tokens are the main components in Python that are
used to read, analyze and create code. They are implemented to understand and
transform Python's code internally. Each token represents a specific syntax
group.
Different tokens used in Python:
1. Keywords: These are words that have a specific
meaning in the Python language and are used specifically in the program. Such
as if, else, while, def.
2. Identifiers: These are the names of variables,
functions or classes in the code. For example, name, age, total_sum.
3. Literals: These are the values that are given in the code as
constants. For example, 5 (integer), "Hello" (string), True
(boolean).
4. Operators: These tokens are used to perform
calculations or organization. For example, + (addition), - (subtraction), *
(multiplication), / (division).
5. Delimiters: These tokens are used to establish the
structure and composition of the code. For example, () (parenthesis), []
(bracket), {} (colon), , (comma), ; (serial).
6. Comments: These are tokens in the program that are
not involved in any program operation, but are used to provide additional
information. In Python, a comment begins with #.
These tokens are fundamental to writing, reading and
understanding Python code.
Question: 2. What are Identifiers? Write their different
naming rules.
Answer: Identifiers are names that are used to identify
objects, functions, variables, classes, modules and other elements used in
code. They represent any type of data in Python. Identifiers are specifically
used in Python programming, such as variable names, function names, class names
etc.
Naming Rules for Identifiers:
1. Identifiers must start with:
·
An identifier can only start with a letter or an
underscore (_).
·
It cannot start with a digit (Example: 123abc is
incorrect).
2. Each identifier can contain only letters, numbers and
underscores:
·
Letters (in English), numbers and underscores
(_) can be used in identifiers.
·
However, identifiers cannot contain some special
characters (like @, #, $).
3. Keywords cannot be used as identifiers in Python:
·
Like if, else, while, return etc.
4. Case Sensitivity in identifiers:
·
Python identifiers are case-sensitive, i.e. name
and Name are different.
5. There is no limit to length:
·
Identifiers can be made of any length, but for
its ease of reading and understanding, short and descriptive identifiers should
be used.
Example:
age = 25 #
Valid identifier
first_name = "John" # Valid identifier
total_sum = 100 #
Valid identifier
123abc = 10 #
Invalid identifier (starts with a number)
if = 5 #
Invalid identifier (reserved keyword)
Thus, properly naming identifiers makes the code better,
readable and easier to understand.
Question:3. What are literals? Create a chart showing the
different types of literals used in Python.
Answer: Literals are values that
are passed directly into Python code. They are actual values that are used to process a
command and act directly in place of a variable or function. Literals mean
constant values that are
used directly as part of the code.
Different types of literals used in Python:
|
Literal
Type |
Example |
Description |
|
Integer
Literal |
10, -50, 0 |
These are
simple positive or negative numbers. |
|
Float
Literal |
3.14, -0.001,
2.0 |
These are
decimal numbers with digits. |
|
String
Literal |
"Hello",
'Python' |
These are
words or sentences written with quotation marks. |
|
Boolean
Literal |
True, False |
These can
only hold two values, True or False. |
|
None
Literal |
None |
These
represent the absence of any variable or value. |
Example:
age = 25 # Integer literal
pi = 3.14 # Float literal
name = "John" # String literal
is_active = True # Boolean literal
data = None # None literal
These literals represent actual values in Python that are directly
given in the code.
Question:4. What are Comments? Write different ways to
write comments in Python.
Answer: Comments are texts that are added to the program
code to enhance the reader's understanding or to temporarily ignore a part.
Comments are not part of the execution of the program and are only there to
help the code reader. Writing comments in Python makes our code easier to
analyze and document.
Ways to write comments in Python:
1. Single-line comment:
The # symbol is used to write a single comment in Python.
All text written after this is a comment and is not understood by the program.
Example:
# This is a single comment
age = 25 # This line is also a comment
2. Multi-line comment:
To write a multi-line comment, text is written with ''' or
""" . It does not directly close the code, but is used to
comment on multiple lines.
Example:
'''
This is a multi-line comment
where we can give more information in multiple lines.
'''
or
"""
This is another multi-line comment
where we can write any special information.
"""
Benefits of comments:
• Comments help in understanding the code.
• They are helpful in documenting parts of the program.
• They are used to temporarily unread or debug the code at
some point.
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