Algorithms, Flowcharts and Pseudocode Class 11: Writing and Reading Solutions

Understand Algorithms, Flowcharts and Pseudocode for Problem Solving

INPUT a, b
IF a > b THEN
    PRINT a
ELSE
    PRINT b
ENDIF

INPUT N
SET sum = 0
SET i = 1
WHILE i <= N DO
    sum = sum + i
    i = i + 1
ENDWHILE
PRINT sum

Algorithms, Flowcharts and Pseudocode for Problem Solving: key facts

Algorithm

• •Finite
• •Precise
• •Unambiguous
• •Defined inputs
• •Defined outputs

Five characteristics.

Flowchart symbols

Oval	start or end
Parallelogram	input or output
Rectangle	process
Diamond	decision
Arrow	flow

Standard shapes.

Control structures

• •Sequence
• •Selection
• •Repetition

Every algorithm is built from these, in any combination.

Pseudocode keywords

• •INPUT
• •PRINT
• •IF THEN ELSE ENDIF
• •WHILE DO ENDWHILE
• •FOR TO DO ENDFOR

Structured English.

How to answer Algorithms, Flowcharts and Pseudocode for Problem Solving questions

1. 1State the inputs and the required output.
2. 2List the steps in order (sequence).
3. 3Mark any decision and write both branches (selection).
4. 4Mark any repeated steps and the stopping condition (repetition).
5. 5Test the algorithm with a small input and an edge case.

Algorithms, Flowcharts and Pseudocode for Problem Solving in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Tricks to remember Algorithms, Flowcharts and Pseudocode for Problem Solving

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Oval, Parallelogram, Rectangle, Diamond

  Terminator, I/O, process, decision.

  Use it when: Flowchart symbols.

• S-S-R

  Sequence, Selection, Repetition.

  Use it when: Control structures.

Algorithms, Flowcharts and Pseudocode for Problem Solving: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Where students lose marks in Algorithms, Flowcharts and Pseudocode for Problem Solving

The slips examiners see most often, and what to write instead.

• ✗Mistake: Using a rectangle for a decision

  Mixing the symbols.

  Wrong working

  Rectangle with yes/no branches.

  Right working

  Diamond with Yes and No branches.

  ✓Do this: Diamond is for decisions.

  Usually costs: 1 mark

• ✗Mistake: No stopping condition

  A loop that never ends.

  Wrong working

  WHILE i <= N DO sum = sum + i ENDWHILE

  Right working

  Add i = i + 1 inside the loop.

  ✓Do this: Every loop must change the tested variable.

  Usually costs: 1 mark

• ✗Mistake: Not stating inputs and outputs

  Jumping to steps.

  Wrong working

  Step 1: add numbers.

  Right working

  INPUT a, b ... PRINT result.

  ✓Do this: State input and output first.

  Usually costs: 1 mark

Practice questions on Algorithms, Flowcharts and Pseudocode for Problem Solving

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   Which of the following is NOT a characteristic of an algorithm?
   (a) finiteness
   (b) ambiguity
   (c) defined input
   (d) defined output

   Hint

   Steps must be clear.

   Answer

   (b) ambiguity

2. Q2 · 4 marks · Short answerHarder board level

   Write pseudocode to find the largest of three numbers. Show the result for 14, 37, 25. (4 marks)

   Hint

   Compare in pairs.

   Answer

   INPUT a, b, c; SET big = a; IF b > big THEN big = b ENDIF; IF c > big THEN big = c ENDIF; PRINT big. For 14, 37, 25: big = 14; 37 > 14 so big = 37; 25 > 37 is false; PRINT 37.

3. Q3 · 3 marks · Short answerHarder board level

   Write pseudocode to print the first 5 multiples of a number n. Give the output for n = 3. (3 marks)

   Hint

   FOR loop.

   Answer

   INPUT n; FOR i = 1 TO 5 DO PRINT n x i ENDFOR. For n = 3 it prints 3, 6, 9, 12, 15.

4. Q4 · 1 mark · Assertion-reasonHarder board level

   Assertion (A): An algorithm must terminate after a finite number of steps.
   Reason (R): An algorithm that never ends cannot give the required output.
   (a) Both A and R are true, and R is the correct explanation of A.
   (b) Both A and R are true, but R is not the correct explanation of A.
   (c) A is true, but R is false.
   (d) A is false, but R is true.

   Hint

   Finiteness.

   Answer

   (a) Both A and R are true, and R is the correct explanation of A.

5. Q5 · 5 marks · Short answerHOTS / competency

   A school fee is ₹5,000 for classes below 6, ₹7,000 for classes 6 to 8 and ₹9,000 above 8. Write the pseudocode to input a class and print the fee, name the control structure and give the fee for classes 3, 8 and 11. (5 marks)

   Hint

   Nested selection.

   Answer

   INPUT c; IF c < 6 THEN fee = 5000 ELSE IF c <= 8 THEN fee = 7000 ELSE fee = 9000 ENDIF ENDIF; PRINT fee. Control structure: selection (nested). Class 3 gives 5000; class 8 gives 7000; class 11 gives 9000.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Symbol for input and output?Show answer

   Parallelogram.

2. 2.Symbol for start and end?Show answer

   Oval.

3. 3.Which structure repeats steps?Show answer

   Repetition (loop).

4. 4.What does GIGO stand for?Show answer

   Garbage in, garbage out.

5. 5.What is pseudocode?Show answer

   Structured English description of an algorithm.

Algorithms, Flowcharts and Pseudocode for Problem Solving: frequently asked questions