NCERT Solutions: Flow of Control — CBSE Class 11 Computer Science

This page provides complete NCERT exercise solutions for CBSE Class 11 Computer Science Chapter 6 — Flow of Control. Every question is answered with a clear explanation and working Python code.

How to Use These Solutions

1. Attempt each question yourself first — write the code on paper or in IDLE before looking at the answer. 2. Compare your approach — check the logic, indentation, variable names, and output format. 3. Understand every line — if anything is unclear, revisit the [chapter guide](/class/11/computer-science/cbse-flow-of-control) for the concept. 4. Run the code — type each program in IDLE and verify the output matches what is shown. 5. Fix your mistakes — record errors in a mistake notebook and re-attempt the question the next day.

Key Concepts Quick Review

Exercise Solutions

Q1. Write a program to check whether a number is even or odd.

# Program to check even or odd
num = int(input("Enter a number: "))
if num % 2 == 0:
    print(f"{num} is even")
else:
    print(f"{num} is odd")

Output:

Q2. Write a program to find the largest of three numbers.

# Program to find the largest of three numbers
a = int(input("Enter first number: "))
b = int(input("Enter second number: "))
c = int(input("Enter third number: "))

if a >= b and a >= c:
    largest = a
elif b >= a and b >= c:
    largest = b
else:
    largest = c

print(f"The largest number is {largest}")

Output:

Q3. Write a program to print the multiplication table of a number entered by the user.

# Program to print multiplication table
num = int(input("Enter a number: "))
print(f"Multiplication table of {num}:")
for i in range(1, 11):
    print(f"{num} x {i} = {num * i}")

Output:

Q4. Write a program to find the factorial of a number using a loop.

# Program to find factorial using for loop
n = int(input("Enter a number: "))

if n < 0:
    print("Factorial is not defined for negative numbers")
else:
    fact = 1
    for i in range(1, n + 1):
        fact *= i
    print(f"Factorial of {n} = {fact}")

Output:

Q5. Write a program to print the Fibonacci series up to n terms.

The Fibonacci series starts with 0 and 1. Each next term is the sum of the two previous terms.

# Program to print Fibonacci series
n = int(input("Enter number of terms: "))

if n <= 0:
    print("Please enter a positive number")
elif n == 1:
    print(0)
else:
    a, b = 0, 1
    print(a, b, end=" ")
    for i in range(2, n):
        c = a + b
        print(c, end=" ")
        a = b
        b = c
    print()

Output:

Q6. Write a program to print the following star pattern:

# Program to print right-angled triangle star pattern
n = int(input("Enter number of rows: "))
for i in range(1, n + 1):
    for j in range(i):
        print("*", end=" ")
    print()

Output:

Q7. Write a program to check whether a number is prime or not.

A prime number is divisible only by 1 and itself. We check divisibility from 2 to n-1.

# Program to check if a number is prime
n = int(input("Enter a number: "))

if n <= 1:
    print(f"{n} is not a prime number")
else:
    for i in range(2, n):
        if n % i == 0:
            print(f"{n} is not a prime number (divisible by {i})")
            break
    else:
        print(f"{n} is a prime number")

Output:

Note: This solution uses the for-else construct. The else block runs only when the loop completes without hitting break, meaning no divisor was found.

Q8. Write a program to find the sum of digits of a number using a while loop.

# Program to find sum of digits
num = int(input("Enter a number: "))
temp = abs(num)  # handle negative numbers
digit_sum = 0

while temp > 0:
    digit_sum += temp % 10
    temp //= 10

print(f"Sum of digits of {num} = {digit_sum}")

Output:

Q9. Write a program to find the reverse of a number using a while loop.

# Program to reverse a number
num = int(input("Enter a number: "))
temp = abs(num)
rev = 0

while temp > 0:
    rev = rev * 10 + temp % 10
    temp //= 10

if num < 0:
    rev = -rev

print(f"Reverse of {num} = {rev}")

Output:

Q10. Write a program to check whether a number is a palindrome.

A palindrome number reads the same forwards and backwards (e.g., 121, 1331).

# Program to check palindrome number
num = int(input("Enter a number: "))
temp = num
rev = 0

while temp > 0:
    rev = rev * 10 + temp % 10
    temp //= 10

if num == rev:
    print(f"{num} is a palindrome")
else:
    print(f"{num} is not a palindrome")

Output:

Q11. Write a program to print all prime numbers between two given numbers using nested loops and break.

# Program to print prime numbers in a range
start = int(input("Enter start of range: "))
end = int(input("Enter end of range: "))

print(f"Prime numbers between {start} and {end}:")
for num in range(start, end + 1):
    if num <= 1:
        continue
    for i in range(2, num):
        if num % i == 0:
            break
    else:
        print(num, end=" ")
print()

Output:

Q12. Write a program to demonstrate the use of break and continue in a loop.

# Program to demonstrate break and continue

# break: find first number divisible by both 3 and 5
print("Using break:")
for i in range(1, 100):
    if i % 3 == 0 and i % 5 == 0:
        print(f"First number divisible by both 3 and 5 is {i}")
        break

# continue: print numbers 1 to 10, skipping multiples of 3
print("\nUsing continue — numbers 1 to 10 (skip multiples of 3):")
for i in range(1, 11):
    if i % 3 == 0:
        continue
    print(i, end=" ")
print()

Output:

Related Pages

• [Flow of Control — Chapter Guide](/class/11/computer-science/cbse-flow-of-control)
• [Getting Started with Python — Chapter Guide](/class/11/computer-science/cbse-getting-started-python)
• [Getting Started with Python — Exercise Solutions](/class/11/computer-science/solutions/cbse-getting-started-python-exercise-solutions)