Computer ApplicationsICSE Class 8 · Algorithms and Flowcharts

Good Algorithm, Development Steps and Flowchart Symbols: ICSE Class 8

Updated 17 October 2026 · Fact-checked

A good algorithm is finite, definite, effective, takes zero or more inputs, gives at least one output and does not depend on a language. You develop it by understanding the problem, finding input and output, planning the process, writing steps from Start to Stop and dry-running it. A flowchart draws it with an oval, parallelogram, rectangle, diamond and arrows.

Follow the arrows from Start to Stop and match each shape to its job: oval ends, parallelogram reads or prints, rectangle calculates, diamond decides.

Illustration drawn for QuestionBuddy.

Understand A Good Algorithm, Its Development Steps and Flowchart Symbols

Where this sits. In the CISCE Class VIII curriculum this is the first half of the theme on algorithms and flowcharts. Decisions inside algorithms are on the next topic page; loops are not part of Class VIII.

Characteristics of a good algorithm.

Input: zero or more values come from outside.
Output: at least one result is produced.
Definiteness: every step means exactly one thing. "Add some sugar" is not definite; "add 2 teaspoons of sugar" is.
Finiteness: the steps end after a limited number of moves. A step that sends you back to step 1 with no way out breaks this.
Effectiveness: every step is simple enough to be carried out.
Language independence: the same algorithm can be coded in any language.

Steps to develop an algorithm.
1. Understand the problem.
2. Identify the input.
3. Identify the output.
4. Plan the process (formula or decisions).
5. Write the steps in order, from Start to Stop.
6. Test with sample data, including boundary values.

Worked shape: area of a circle. Input radius R; process Area = 3.14 x R x R; output Area. For R = 10: 3.14 x 10 x 10 = 314. (The value 3.14 for pi is an assumption chosen for this page.)

Flowchart symbols.

Symbol	Shape	Used for
Terminal	oval	Start and Stop
Input/Output	parallelogram	reading and printing
Process	rectangle	calculations
Decision	diamond	Yes/No question, two exits
Flow line	arrow	order of steps
Connector	small circle	joining parts

Drawing rules. One Start and at least one Stop; flow top to bottom or left to right; a diamond has one entry and two labelled exits (Yes and No); every path must reach Stop; short text in each box.

Algorithm versus program. An algorithm is a plan in plain language; a program is that plan written in a programming language. Errors in logic are cheaper to find in the plan.

A Good Algorithm, Its Development Steps and Flowchart Symbols: key facts

Characteristics of a good algorithm: Input
Output
Definiteness
Finiteness
Effectiveness
Language independence; Output must be at least one value; input may be zero.
Steps to develop an algorithm: Understand
Input
Output
Process
Write steps
Test; Always end with a dry run using boundary values.
Flowchart symbols: Oval Start/Stop
Parallelogram Input/Output
Rectangle Process
Diamond Decision
Arrow Flow; The diamond is the only symbol with two exits.

Oval	Start/Stop
Parallelogram	Input/Output
Rectangle	Process
Diamond	Decision
Arrow	Flow

How to answer A Good Algorithm, Its Development Steps and Flowchart Symbols questions

Use this routine to write and check an algorithm.

1Write the problem in one line and list its inputs and its output.
2Decide the formula or the decision needed.
3Write numbered steps beginning with Start and ending with Stop, each step doing one thing.
4Draw the matching symbol for each step and join them with arrows.
5Dry-run with two sample values, one of them a boundary value, and check the output.

A Good Algorithm, Its Development Steps and Flowchart Symbols 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.

Planning a school trip budget

Suppose a class teacher in a hypothetical school plans a trip and needs the cost per student. The bus costs 6000 rupees and 40 students will go.

Write the algorithm and test it.

Try it first, then show the solutionSolution

Input: total cost C and number of students N.
Process: share = C / N.
Output: print share.
Test: 6000 / 40 = 150.

Answer: Each student pays 150 rupees. The algorithm has input, process and output, ends after a few steps, and every step is exact.

Memory hook: Input, process, output: every algorithm has this shape.

Tricks to remember A Good Algorithm, Its Development Steps and Flowchart Symbols

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

DEFI + IO
Definiteness, Effectiveness, Finiteness, Independence of language, plus Input and Output.
Use it when: Listing the characteristics.
Oval, slanted box, box, diamond
Oval starts and stops, slanted box talks (input/output), plain box works, diamond decides.
Use it when: Matching symbols to steps.

A Good Algorithm, Its Development Steps and Flowchart Symbols: solved examples

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

Example 1: Symbol for a decision · 1 mark · MCQBoard level

Which flowchart symbol has one entry and two exits labelled Yes and No?
(a) Oval (b) Parallelogram (c) Rectangle (d) Diamond

Try it first, then show the solutionSolution

Only a decision step branches in two.

Answer: (d) Diamond.

Example 2: Which characteristic is broken? · 2 marks · Short answerBoard level

Name the characteristic of a good algorithm that is broken by each: (i) "Add some sugar." (ii) A step that says "Go back to step 1" with no way to stop. (2 marks)

Try it first, then show the solutionSolution

(i) The amount is unclear, so it is not definite (1).
(ii) The steps never end, so finiteness is broken (1).

Answer: (i) Definiteness. (ii) Finiteness.

Example 3: Algorithm for the average of three numbers · 3 marks · Long answerHarder board level

Write an algorithm to find the average of three numbers A, B and C, and test it with 12, 18 and 30. (3 marks)

Try it first, then show the solutionSolution

Start; input A, B, C (1).
Avg = (A + B + C) / 3; print Avg; stop (1).
Test: (12 + 18 + 30) = 60; 60 / 3 = 20 (1).

Answer: 1. Start. 2. Input A, B, C. 3. Avg = (A + B + C) / 3. 4. Print Avg. 5. Stop. For 12, 18, 30 the output is 20.

Example 4: Choosing symbols for a circle-area flowchart · 4 marks · Long answerHarder board level

An algorithm has these steps: Start; Input radius R; Area = 3.14 x R x R; Print Area; Stop. Name the flowchart symbol for each step and give the output for R = 10. (4 marks)

Try it first, then show the solutionSolution

Start and Stop: oval (1).
Input R and Print Area: parallelogram (1).
Area = 3.14 x R x R: rectangle (1).
3.14 x 10 x 10 = 314 (1).

Answer: Oval for Start and Stop, parallelogram for the input and the print step, rectangle for the calculation. Output for R = 10: 314.

Example 5: Find the faults · 4 marks · Long answerHOTS / competency

A student writes: 1. Start 2. Input marks 3. If marks >= 40 print Pass 4. Stop. Test it with 39 and 40, state what is wrong, and correct it. (4 marks)

Try it first, then show the solutionSolution

40 prints Pass (1).
39 prints nothing, so the algorithm gives no output for a failing student (1).
The decision needs a second path, so it should print Fail otherwise (1).
Corrected step 3: if marks >= 40 print Pass else print Fail (1).

Answer: For 39 the algorithm prints nothing, so it does not always produce an output. Correct step 3 to: if marks >= 40 print Pass, else print Fail. Then 40 gives Pass and 39 gives Fail.

Where students lose marks in A Good Algorithm, Its Development Steps and Flowchart Symbols

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

Mistake: Saying an algorithm may have no output
Every algorithm must give at least one result.
Wrong working
Input: zero or more; Output: zero or more.
Right working
Input: zero or more; Output: at least one.
Do this: Remember that input may be zero but output may not.
Usually costs: 1 mark
Mistake: Using a rectangle for input
Input and output use the parallelogram.
Wrong working
Input N drawn in a rectangle.
Right working
Input N drawn in a parallelogram.
Do this: Learn the slanted box talks.
Usually costs: 1 mark
Mistake: Testing with only one easy value
Boundary values catch decision errors.
Wrong working
Testing marks >= 40 only with 75.
Right working
Testing with 40 and 39.
Do this: Always include the boundary.
Usually costs: 1 mark

Exam tips

Write Start and Stop in every algorithm and flowchart.
Name the symbol and its use together in short answers.
Show a dry run with real numbers; examiners reward it.
Keep each step to one action in simple language.

Practice questions on A Good Algorithm, Its Development Steps and Flowchart Symbols

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

Q1 · 1 mark · MCQBoard level
Which of these is NOT a characteristic of a good algorithm?
(a) Finiteness (b) Definiteness (c) It must be written in Java (d) Effectiveness
Hint
An algorithm is language independent.
Answer
(c) It must be written in Java.
Q2 · 3 marks · Short answerBoard level
A pupil must write an algorithm to find the perimeter of a square. State what she writes for the input, the output and the process, and name the last of the six development steps. (3 marks)
Hint
Think of the six steps.
Answer
Input: the side S. Output: the perimeter. Process: Perimeter = 4 x S. The last step is to test the algorithm with sample data, for example S = 5 gives 20.
Q3 · 4 marks · Long answerHarder board level
Write an algorithm to convert a temperature from degrees Celsius to degrees Fahrenheit using F = C x 9 / 5 + 32, and test it with 100 and 0. (4 marks)
Hint
Two tests, one of them zero.
Answer
1. Start. 2. Input C. 3. F = C x 9 / 5 + 32. 4. Print F. 5. Stop. For C = 100: 100 x 9 / 5 = 180, plus 32 gives 212. For C = 0: 32.
Q4 · 3 marks · Short answerHarder board level
A flowchart has two Start ovals and a diamond with only one exit arrow. State two errors and how to correct each. (3 marks)
Hint
Drawing rules.
Answer
There must be exactly one Start, so the second Start should be removed. A diamond needs two exits labelled Yes and No, so the missing exit should be added and labelled.
Q5 · 4 marks · Long answerHOTS / competency
Rewrite the step "Cook the rice for a while" so that it is definite and effective, and explain why your version is better. (4 marks)
Hint
Give an exact time and an exact check.
Answer
For example: "Cook the rice on a low flame for 15 minutes, then press a grain to check that it is soft." This is definite because the time is exact, and effective because each action can really be done. The original does not say how long, so two people would do different things.

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.What is an algorithm?Show answer
A finite sequence of clear, step-by-step instructions to solve a problem.
2.Which symbol marks Start and Stop?Show answer
The oval (terminal).
3.Which symbol is used for input and output?Show answer
The parallelogram.
4.How many exits does a decision diamond have?Show answer
Two, labelled Yes and No.
5.What is a dry run?Show answer
Testing the algorithm by hand with sample data.
6.Is an algorithm tied to one language?Show answer
No, it is language independent.

A Good Algorithm, Its Development Steps and Flowchart Symbols: frequently asked questions

Are loops part of Class VIII algorithms?

No. The curriculum asks for sequence and decision making only; loops are excluded.

Can an algorithm have no input?

Yes, input can be zero, but output must be at least one.

Is the flowchart or the algorithm written first?

Usually the algorithm is written first and the flowchart is its picture; either way they must match step by step.