Flow of Control

This page contains the NCERT Computer Science class 11 chapter 6 Flow of Control. You can find the solutions for the chapter 6 of NCERT class 11 Computer Science Exercise. So is the case if you are looking for NCERT class 11 Computer Science related topic Flow of Control questions and answers for the Exercise

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Exercise

1) What is the difference between else and elif construct of if statement?

1) `else`

•

`else` is the default (alternative) block.

•

It runs only when the `if` (and all `elif`, if present) conditions are False.

•

No condition is written with `else`.

Syntax:

if condition:
    statements
else:
    statements

2) `elif`

•

`elif` means “else if”.

•

It is used to check one more condition when the previous `if` condition is False.

•

You can write many `elif` blocks (as needed).

•

Each `elif` has its own condition.

Syntax:

if condition1:
    statements
elif condition2:
    statements
elif condition3:
    statements
else:
    statements

Key differences (quick comparison)

Basis

`elif`

`else`

Condition needed?

✅ Yes

❌ No

Purpose

Check another condition

Runs when no condition is true

How many times can we use?

Many `elif`

Only one `else` (optional)

Position

Between `if` and `else`

Always at the end

In an `if–elif–else` chain, only one block runs: the first condition that becomes True; otherwise `else` runs.

Example

marks = int(input("Enter marks: "))

if marks >= 90:
    print("Grade A")
elif marks >= 80:
    print("Grade B")
else:
    print("Grade C")

•

If `marks` is 92 → Grade A

•

If `marks` is 85 → Grade B

•

If `marks` is 70 → Grade C

2) What is the purpose of range() function? Give one example.

The purpose of `range()` is to generate a sequence of integers (numbers) which is commonly used in a `for` loop.

•

`range(start, stop, step)`

•

stop is not included

for i in range(1, 6):
    print(i)

This prints:

3) Differentiate between break and continue statements using examples.

In Python, `break` and `continue` are loop control statements used inside `for` and `while` loops to change the normal flow of execution.

1) `break` statement

•

Meaning: Stop the loop immediately.

•

When `break` is executed, the loop terminates at once, and control comes outside the loop.

Example (`break` in a `for` loop):

for i in range(1, 6):
    if i == 4:
        break
    print(i)
print("Loop ended")

Output:

1
2
3
Loop ended

✅ Here, as soon as `i` becomes 4, the loop stops completely.

2) `continue` statement

•

Meaning: Skip the current iteration and move to the next one.

•

When `continue` is executed, Python skips the remaining statements of that iteration and jumps to the next iteration of the loop.

Example (`continue` in a `for` loop):

for i in range(1, 6):
    if i == 4:
        continue
    print(i)
print("Loop ended")

Output:

1
2
3
5
Loop ended

✅ Here, when `i` becomes 4, only that iteration is skipped, but the loop continues for 5.

Key Difference (Quick Comparison)

Basis

`break`

continue`

What it does

Ends the loop immediately

Skips the current iteration

Control goes to

Outside the loop

Next iteration of the loop

Loop runs further?

❌ No

✅ Yes

(Extra) Same idea using a `while` loop

`break` in `while`:

i = 1
while i <= 5:
    if i == 4:
        break
    print(i)
    i += 1

Output:

1
2
3

`continue` in `while`:

i = 0
while i < 5:
    i += 1
    if i == 4:
        continue
    print(i)

Output:

4) What is an infinite loop? Give one example.

An infinite loop is a loop that never stops because its condition never becomes false.

Example:

while True:
    print("This will run forever")

5) Find the output of the following program segments:

(i)

a = 110

while a > 100:

print(a)

a -= 2

(ii)

for i in range(20,30,2):

print(i)

(iii)

country = 'INDIA'

for i in country:

print (i)

(iv)

i = 0; sum = 0

while i < 9:

if i % 4 == 0:

sum = sum + i

i = i + 2

print (sum)

(v)

for x in range(1,4):

for y in range(2,5):

if x * y > 10:

break

print (x * y)

(vi)

var = 7

while var > 0:

print ('Current variable value: ', var)

var = var -1

if var == 3:

break

else:

if var == 6:

var = var -1

continue

print ("Good bye!")

(i) Code:

a = 110
while a > 100:
    print(a)
    a -= 2

Output:

(ii) Code:

for i in range(20, 30, 2):
    print(i)

Output:

(iii) Code:

country = 'INDIA'
for i in country:
    print(i)

Output:

I
N
D
I
A

(iv) Code:

i = 0; sum = 0
while i < 9:
    if i % 4 == 0:
        sum = sum + i
    i = i + 2
print(sum)

Working (values of i): 0, 2, 4, 6, 8

Add only when divisible by 4 → 0 + 4 + 8 = 12

Output:

(v) Code:

for x in range(1,4):
    for y in range(2,5):
        if x * y > 10:
            break
        print(x * y)

Output:

(vi) Code:

var = 7
while var > 0:
    print('Current variable value: ', var)
    var = var - 1
    if var == 3:
        break
    else:
        if var == 6:
            var = var - 1
            continue
        print ("Good bye!")

Output:

Current variable value:  7
Current variable value:  5
Good bye!
Current variable value:  4

Programming Exercises

1) Write a program that takes the name and age of the user as input and displays a message whether the user is eligible to apply for a driving license or not. (the eligible age is 18 years).

# Program to check driving license eligibility
# Eligible age = 18 years

name = input("Enter your name: ")
age = int(input("Enter your age: "))

if age >= 18:
    print(name + ", you are eligible to apply for a driving license.")
else:
    print(name + ", you are not eligible to apply for a driving license.")

Sample Output (Example)

Case 1 (Eligible):

Enter your name: Rahul
Enter your age: 19
Rahul, you are eligible to apply for a driving license.

Case 2 (Not Eligible):

Enter your name: Asha
Enter your age: 16
Asha, you are not eligible to apply for a driving license.

2) Write a function to print the table of a given number. The number has to be entered by the user.

✅ Program (Python)

# Function to print the multiplication table of a number
def print_table(n):
    """This function prints the table of the given number from 1 to 10."""
    for i in range(1, 11):
        print(n, "x", i, "=", n * i)

# Taking input from the user
num = int(input("Enter a number: "))

# Calling the function
print_table(num)

Sample Output

Enter a number: 7
7 x 1 = 7
7 x 2 = 14
7 x 3 = 21
7 x 4 = 28
7 x 5 = 35
7 x 6 = 42
7 x 7 = 49
7 x 8 = 56
7 x 9 = 63
7 x 10 = 70

3) Write a program that prints minimum and maximum of five numbers entered by the user.

✅ Program (Python) — All 5 inputs inside the `for` loop (No lists, no `min()`/`max()`)

# Program to input five numbers and print the minimum and maximum
# All five numbers will be taken inside a for loop.

# We will use two variables: minimum and maximum
# For the first number, we will set both minimum and maximum to that number.
# From the second number onward, we will compare and update.

minimum = None  # not set yet
maximum = None  # not set yet

# Loop runs 5 times to take 5 numbers as input
for i in range(1, 6):
    num = int(input("Enter number " + str(i) + ": "))

    # If this is the first number, set both minimum and maximum
    if i == 1:
        minimum = num
        maximum = num
    else:
        # Compare with current minimum
        if num < minimum:
            minimum = num

        # Compare with current maximum
        if num > maximum:
            maximum = num

# Print final answers
print("Minimum =", minimum)
print("Maximum =", maximum)

Sample Output

Enter number 1: 25
Enter number 2: 11
Enter number 3: 78
Enter number 4: 4
Enter number 5: 50
Minimum = 4
Maximum = 78

4) Write a program to check if the year entered by the user is a leap year or not.

✅ Program (Python)

# Program to check if a given year is a leap year or not
# A year is a leap year if:
#   1. It is divisible by 400, OR
#   2. It is divisible by 4 AND NOT divisible by 100

year = int(input("Enter a year: "))

if (year % 400 == 0) or (year % 4 == 0 and year % 100 != 0):
    print(year, "is a leap year")
else:
    print(year, "is not a leap year")

Sample Output

Case 1 (Leap Year):

Enter a year: 2020
2020 is a leap year

Case 2 (Not a Leap Year):

Enter a year: 2021
2021 is not a leap year

5) Write a program to generate the sequence: –5, 10, –15, 20, –25….. upto n, where n is an integer input by the user.

(Here, we generate n terms.)

✅ Program (Python)

# Program to generate the sequence: -5, 10, -15, 20, -25, ...
# Pattern: Multiply index by 5, then alternate signs (odd indices are negative, even are positive)

n = int(input("Enter n (number of terms): "))

# Loop from 1 to n (inclusive)
for i in range(1, n + 1):
    term = 5 * i  # Multiply by 5 to get magnitude: 5, 10, 15, 20, 25, ...
    
    # Check if i is odd (index 1, 3, 5, ... are negative)
    if i % 2 == 1:
        term = -term  # Make it negative for odd positions
    
    print(term, end=" ")  # Print with space separator

Sample Output

Enter n (number of terms): 7
-5 10 -15 20 -25 30 -35

6) Write a program to find the sum of 1 + 1/8 + 1/27……1/n³, where n is the number input by the user.

✅ Program (Python)

# Program to find the sum: 1/1³ + 1/2³ + 1/3³ + ... + 1/n³

n = int(input("Enter n: "))
s = 0.0  # Initialize sum to 0.0 (float for decimal calculations)

# Loop from 1 to n (inclusive)
for i in range(1, n + 1):
    s += 1 / (i ** 3)  # Add 1/i³ to the sum (i**3 means i cubed)

print("Sum =", s)

Sample Output

Enter n: 4
Sum = 1.1776785714285714

7) Write a program to find the sum of digits of an integer number, input by the user.

✅ Program (Python)

# Program to find the sum of digits of an integer number
# Use % 10 to get last digit, // 10 to remove it

num = int(input("Enter an integer: "))
num = abs(num)   # Handle negative numbers by taking absolute value
s = 0  # Initialize sum to 0

# Extract digits one by one from right to left
while num > 0:
    digit = num % 10  # Get the last digit
    s += digit  # Add it to sum
    num //= 10  # Remove the last digit

# Step 5: Display the result
print("Sum of digits =", s)

Sample Output

Example 1:

Enter an integer: 238
Sum of digits = 13

Example 2:

Enter an integer: 507
Sum of digits = 12

8) Write a function that checks whether an input number is a palindrome or not.

[Note: A number or a string is called palindrome if it appears same when written in reverse order also. For example, 12321 is a palindrome while 123421 is not a palindrome]

✅ Program (Python)

# Program to check whether a number is a palindrome or not
# Reverse the number using % (modulus) and // (floor division)
# and then compare it with the original number

num = int(input("Enter a number: "))

# Negative numbers are not treated as palindrome
if num < 0:
    print(num, "is not a palindrome number.")
else:
    original = num   # Store the original number safely
    reverse = 0      # This will store the reversed number

    # Reverse the number digit by digit
    while num > 0:
        digit = num % 10              # Get the last digit
        reverse = reverse * 10 + digit
        num = num // 10               # Remove the last digit

    # Compare original number with reversed number
    if reverse == original:
        print(original, "is a palindrome number.")
    else:
        print(original, "is not a palindrome number.")

Sample Output

Case 1 (Palindrome):

Enter a number: 12321
12321 is a palindrome number.

Case 2 (Not Palindrome):

Enter a number: 456
456 is not a palindrome number.

9) Write a program to print the following patterns:

(i)

*
* * *
* * * * *
* * *
*

(ii)

1
2 1 2
3 2 1 2 3
4 3 2 1 2 3 4
5 4 3 2 1 2 3 4 5

(iii)

1 2 3 4 5
1 2 3 4
1 2 3
1 2
1

(iv)

*
* *
* *
* *
*

(i) Filled Diamond of `*`

# Pattern (i): Filled diamond using stars

n = 3  # middle row will have (2*n - 1) stars -> 5

# Top half (including middle row)
for i in range(1, n + 1):
    # Print spaces before stars
    for sp in range(n - i):
        print("  ", end="")

    # Print stars in odd count: 1, 3, 5 ...
    for st in range(2 * i - 1):
        print("* ", end="")
    print()  # move to next line

# Bottom half
for i in range(n - 1, 0, -1):
    # Print spaces before stars
    for sp in range(n - i):
        print("  ", end="")

    # Print stars in odd count: 3, 1 ...
    for st in range(2 * i - 1):
        print("* ", end="")
    print()

Output:

    *
  * * *
* * * * *
  * * *
    *

(ii) Number Pyramid (Decreasing then Increasing)

# Pattern (ii): Number pyramid
# Each row prints: spaces, decreasing numbers (i to 1), increasing numbers (2 to i)

n = 5

for i in range(1, n + 1):

    # Print spaces (each space block is "  " for alignment)
    for sp in range(n - i):
        print("  ", end="")

    # Print decreasing numbers: i, i-1, ..., 2, 1
    for k in range(i, 0, -1):
        print(k, end=" ")

    # Print increasing numbers: 2, 3, ..., i
    for j in range(2, i + 1):
        print(j, end=" ")

    print()  # next line

Output:

        1
      2 1 2
    3 2 1 2 3
  4 3 2 1 2 3 4
5 4 3 2 1 2 3 4 5

(iii) Decreasing Rows of `1 2 3 …`

# Pattern (iii): Print numbers from 1 to i, but rows decrease from 5 to 1

n = 5

for i in range(n, 0, -1):      # i = 5, 4, 3, 2, 1
    for j in range(1, i + 1):  # print 1 to i
        print(j, end=" ")
    print()                    # next line

Output:

(iv) Hollow Diamond of `*`

# Pattern (iv): Hollow diamond outline using stars

n = 3  # half height

# Top part (rows 1 to n-1)
for i in range(1, n):
    # Spaces before first star
    for sp in range(n - i):
        print("  ", end="")

    print("*", end="")  # first star

    # Spaces between two stars (only from row 2 onward)
    if i > 1:
        for mid in range(2 * i - 3):
            print("  ", end="")
        print("*", end="")  # second star

    print()  # next line

# Middle row (always two stars with gap)
print("*", end="")
for mid in range(2 * n - 3):
    print("  ", end="")
print("*")

# Bottom part (rows n-1 down to 1)
for i in range(n - 1, 0, -1):
    # Spaces before first star
    for sp in range(n - i):
        print("  ", end="")

    print("*", end="")  # first star

    if i > 1:
        for mid in range(2 * i - 3):
            print("  ", end="")
        print("*", end="")  # second star

    print()

Output:

    *
  *   *
*       *
  *   *
    *

9. Write a program to find the grade of a student when grades are allocated as given in the table below.

Percentage of Marks

Grade

Above 90%

80% to 90%

70% to 80%

60% to 70%

Below 60%

Percentage of the marks obtained by the student is input to the program.

# Read percentage of marks from the user
p = float(input("Enter percentage: "))

# Decide grade based on the given ranges
if p > 90:
    print("Grade A")
elif p >= 80:
    print("Grade B")
elif p >= 70:
    print("Grade C")
elif p >= 60:
    print("Grade D")
else:
    print("Grade E")

Sample Run Output (Example 1)

Enter percentage: 95
Grade A

Sample Run Output (Example 2)

Enter percentage: 85
Grade B

Sample Run Output (Example 3)

Enter percentage: 55
Grade E

Case Study-based Question

Let us add more functionality to our SMIS developed in Chapter 5.

6.1 Write a menu driven program that has options to

•

accept the marks of the student in five major subjects in Class X and display the same.

•

calculate the sum of the marks of all subjects. Divide the total marks by number of subjects (i.e. 5), calculate percentage = total marks/5 and display the percentage.

•

Find the grade of the student as per the following criteria:

Criteria

Grade

percentage > 85

percentage < 85 && percentage >= 75

percentage < 75 && percentage >= 50

percentage > 30 && percentage <= 50

percentage < 30

Reappear

Let’s peer review the case studies of others based on the parameters given under “DOCUMENTATION TIPS” at the end of Chapter 5 and provide a feedback to them.

# SMIS menu-driven program: accept marks, compute total/percentage and grade
marks = []
total = 0
percentage = 0

while True:
    # display menu options to the user
    print("\n--- SMIS MENU ---")
    print("1. Accept marks (5 subjects) and display")
    print("2. Calculate total and percentage")
    print("3. Display grade")
    print("4. Exit")

    choice = int(input("Enter your choice (1-4): "))

    # Option 1: accept marks for 5 subjects
    if choice == 1:
        marks = []
        # read marks into the list
        for i in range(5):
            m = float(input(f"Enter marks for subject {i+1}: "))
            marks.append(m)
        print("Marks entered:", marks)

    # Option 2: calculate total and percentage
    elif choice == 2:
        if len(marks) != 5:
            print("Please enter marks first using option 1.")
        else:
            total = sum(marks)
            percentage = total / 5
            print("Total marks =", total)
            print("Percentage =", percentage)

    # Option 3: compute and display grade based on percentage
    elif choice == 3:
        if len(marks) != 5:
            print("Please enter marks first using option 1.")
        else:
            # if percentage not calculated yet, calculate it
            total = sum(marks)
            percentage = total / 5

            # determine grade using the given ranges
            if percentage > 85:
                grade = "A"
            elif percentage < 85 and percentage >= 75:
                grade = "B"
            elif percentage < 75 and percentage >= 50:
                grade = "C"
            elif percentage > 30 and percentage <= 50:
                grade = "D"
            else:
                grade = "Reappear"

            print("Percentage =", percentage)
            print("Grade =", grade)

    # Option 4: exit the program
    elif choice == 4:
        print("Exiting... Bye Bye!!")
        break

    # invalid choice handling
    else:
        print("Wrong choice. Please enter between 1 and 4.")

Sample Output

--- SMIS MENU ---
1. Accept marks (5 subjects) and display
2. Calculate total and percentage
3. Display grade
4. Exit
Enter your choice (1-4): 1
Enter marks for subject 1: 82
Enter marks for subject 2: 90
Enter marks for subject 3: 75
Enter marks for subject 4: 88
Enter marks for subject 5: 80
Marks entered: [82.0, 90.0, 75.0, 88.0, 80.0]

--- SMIS MENU ---
1. Accept marks (5 subjects) and display
2. Calculate total and percentage
3. Display grade
4. Exit
Enter your choice (1-4): 2
Total marks = 415.0
Percentage = 83.0

--- SMIS MENU ---
1. Accept marks (5 subjects) and display
2. Calculate total and percentage
3. Display grade
4. Exit
Enter your choice (1-4): 3
Percentage = 83.0
Grade = B

--- SMIS MENU ---
1. Accept marks (5 subjects) and display
2. Calculate total and percentage
3. Display grade
4. Exit
Enter your choice (1-4): 4
Exiting... Bye Bye!!