Software Development Life Cycle

Learning Objectives

• Define an algorithm and state its characteristics.
• Describe the standard flowchart symbols.
• Draw flowcharts for sequence and for a decision.
• Turn an everyday task into ordered steps and a diagram.

Starter Scenario

A pupil wants to make a cup of hot tea. If the steps are jumbled, such as pouring the water before boiling it, the result is wrong. Clear, ordered steps are needed to succeed. A clear set of ordered steps to complete a task is called an algorithm, and computers depend on it completely.

What is an Algorithm

An algorithm is a step by step set of instructions for solving a problem or completing a task. Each step is simple and clear, and the steps are followed in a precise order. In cooking, a recipe is an algorithm because it lists exact ingredients and steps in order. In travel, a route description is an algorithm. In a computer, a program is an algorithm written in a language the computer understands. The key idea is that an algorithm is a plan, and the same plan can be written down in words, in pictures, or in a programming language.

Everyday examples of algorithms include the steps to brush your teeth, which are wet the brush, add paste, brush, rinse and spit. The steps to buy airtime are open the app, enter the amount, confirm and type the code. The steps to line up for assembly are stand in class order, walk out, stand in line and wait. In each one the order matters, because doing a step out of place changes the result.

Characteristics of a Good Algorithm

A good algorithm should be clear, so every step is easy to understand. It should be unambiguous, so each step has only one meaning. It should be finite, so it ends after a certain number of steps. It should be precise, so the input and output are well defined. It should be effective, so every step can actually be carried out. It should be ordered, so steps run from start to finish in a correct sequence. A good algorithm should produce the same correct result every time when followed carefully.

What is a Flowchart

A flowchart is a diagram that shows the steps of an algorithm using standard symbols joined by arrows. It lets you see the whole process at a glance and makes errors easy to spot. Using standard shapes matters because a rectangle always means the same thing to any reader, just as road signs share one meaning for all drivers. To read a flowchart, start at the first oval, move along the arrows, carry out each process you pass, check each decision, and follow the correct branch until you reach the end oval. The arrows are essential because they tell the reader which step comes next.

Drawing Simple Flowcharts

A sequence flowchart shows steps that always happen one after another with no choices. To draw one, write the start oval, then each action in a rectangle, then the end oval, all joined by arrows. For example, making a fruit drink follows the sequence Start, take a cup, pour the juice, add sugar, stir, and End. Each step is one rectangle in a straight chain. When drawing, keep one step in each shape, write short clear words, and always draw an arrow from one shape to the next.

When a flow can go two ways, add a diamond for the decision. The question inside must be answerable with yes or no, and two arrows leave the diamond, one for yes and one for no, each leading to the right next step. For example, going to school follows the sequence Start, check whether it is raining, if yes carry an umbrella then leave, if no leave directly, reach school and End. The diamond sends the flow down one of two branches. Clear labels on the two arrows, such as yes and no, stop the reader from guessing which path to take.

Any algorithm can be turned into a flowchart by changing each word step into its matching symbol. Simple actions become rectangles, questions become diamonds, and the order becomes arrows. Drawing the flowchart by hand first, using a ruler and pencil, is a reliable way to keep the shapes neat and the arrows straight.

Algorithmic Thinking

Algorithmic thinking is the habit of breaking a problem into small, clear steps and putting those steps in the right order. People use algorithmic thinking every day without knowing its name, when a cook follows a recipe, when a student lists the steps for getting to school, and when a trader counts change in a fixed way.

When a task is broken down like this, the set of ordered steps is called an algorithm. A good algorithm has four important characteristics. It is definite, so each step has one clear meaning. It is finite, so it has a definite end and does not run forever. It produces output, so the user gets a visible result at the end. And it is effective, so every step can actually be carried out.

Definite, every step has one clear meaning.

Finite, the steps come to an end after a certain number.

Output, the algorithm produces a result the user can see.

Effective, each step can really be carried out.

Algorithmic thinking is the thinking skill behind programming. In this week's periods learners will write algorithms, draw them as flowcharts, and prepare for writing real programmes in Week 10.

Flowchart Symbols and Their Meanings

A flowchart is drawn with standard shapes, and every shape has one fixed meaning, so any reader understands the picture. The main symbols are the oval, the rectangle, the diamond, the arrow and the parallelogram.

The oval, also called the terminal, marks the start and the end of the flowchart. Every flowchart begins with a start oval and finishes with a stop oval. The rectangle, called the process box, shows an action or step such as add the sugar or print the receipt. The diamond, called the decision box, asks a question that can be answered yes or no, such as Is it raining? The arrow, called the flow line, connects the shapes and shows the direction in which the steps move. The parallelogram, called the input or output box, shows data entering or leaving the computer, such as type the number or display the answer.

Oval, start and end of the flowchart.

Rectangle, an action or process step.

Diamond, a yes or no decision.

Arrow, the direction of flow between steps.

Parallelogram, input or output of data.

Learners should match every part of an algorithm to its correct symbol, so that a word step becomes the right shape on the diagram.

Reading a Flowchart

To read a flowchart, begin at the first oval and follow the arrows from shape to shape. At a rectangle, carry out the action it describes. At a diamond, answer the question and follow the branch that matches, yes or no. The reading ends at the stop oval.

Reading skills help learners check their own diagrams and spot mistakes. If an arrow points the wrong way, or a decision has no yes or no label, the flowchart will send the reader the wrong way, just as an incorrect recipe step ruins the meal.

Start at the first oval and follow the arrows.

Do what each rectangle says, one step after another.

At a diamond, answer the question and follow the correct branch.

Finish when the stop oval is reached.

Constructing Flowcharts for Everyday Tasks

Constructing a flowchart follows a simple method. First write the steps of the task in order as plain sentences. Then decide which shape each step needs. Finally draw the shapes with a ruler and pencil, link them with arrows, and check by reading the finished picture from start to end.

For example, consider the task of getting ready for school. The main steps can be listed as start, wake up, brush teeth, dress, check whether breakfast is ready, and go to school. The decision Is breakfast ready? is a diamond with two branches. If yes, eat breakfast and then go to school. If no, go to school directly.

Using a ruler and pencil keeps the shapes neat. Each shape should hold one short step, and every arrow should point clearly to the next shape. A flowchart with one step per shape is far easier to read and to turn into code later.

Flowcharts for Simple Computations

Flowcharts are also used for simple computations, tasks where the computer takes a number, works on it and shows an answer. A common example is finding the area of a rectangle.

The flowchart reads as follows. Start. Read the length L and the width W of the rectangle, shown in parallelograms. Process the calculation, Area equals L times W, shown in a rectangle. Finally display the area, shown in a parallelogram, and stop. This pattern, input, process, output, is the shape of nearly every simple computation.

Read the two input values in parallelograms.

Calculate in a process rectangle, such as Area equals L times W.

Display the result and stop.

Learners can repeat this pattern for other computations, such as finding the total cost of items or converting miles to kilometres, which strengthens the link between flowcharts and real programmes.

Practical Work

1. Write the steps for making a fruit drink as an ordered algorithm.
2. Draw a flowchart with a decision for whether to carry an umbrella.
3. Match each flowchart symbol with its meaning.
4. Write the algorithm for buying airtime in four clear steps.

Scenario-Based Questions

1. A pupil wants to make a cup of tea but writes the steps in this order: drink the tea, boil water, put tea bag in cup, pour boiling water. Explain why this algorithm fails and rewrite the steps in the correct order.
2. A school wants a flowchart that asks a pupil for their class. If the class is JSS 3, the flowchart prints Welcome to JSS 3. For any other class, it prints Sorry, this system is for JSS 3 only. Identify which flowchart symbol you would use for each step and draw the flowchart.
3. A farmer wants an algorithm to decide whether to irrigate his crops. The rule is: if the soil moisture is below 30 percent, irrigate; otherwise, do not irrigate. Write the algorithm and say which flowchart symbol represents the decision.
4. A teacher says an algorithm must have a start and an end. Explain why an algorithm without a clear end point can cause problems and give an example of an everyday task with a definite end.
5. A pupil draws a flowchart but uses rectangles for decisions and diamonds for processes. Identify the mistake, explain the correct use of each symbol, and say why using the wrong symbol confuses the reader.
6. A library needs an algorithm to check if a borrower can take a book. The rules are: if the borrower has fewer than 3 books and the book is not reserved, the borrower can take it. Otherwise, the borrower cannot. Write the algorithm in steps and identify the decisions.
7. A beginner programmes a robot to move forward, turn left and pick up an object. Write a simple algorithm with exactly five steps and suggest what flowchart symbols would be used for each step.

Lesson objectives

By the end of the week, learners should be able to:

1. Define the software development life cycle and its phases.
2. Name the eight phases in order.
3. Compare waterfall and agile models on flexibility.
4. Describe the testing phase and its purpose.
5. Draw a simple waterfall lifecycle chart showing all phases.

Key vocabulary

• Software development life cycle: the ordered stages of building software.
• Phase: one stage in the development process.
• Waterfall: a linear model moving strictly through stages once.
• Agile: an iterative model repeating cycles of planning, building and testing.
• Testing phase: verification checking the product works correctly.
• Verification: confirming the product meets requirements.
• Validation: confirming the product meets user needs.
• Linear model: a model progressing strictly through stages without loops.

Common misconceptions

• "Waterfall never revisits earlier phases." Waterfall revisits earlier phases on major defects.
• "Agile is chaotic development." Agile has disciplined iteration cycles inside loops.
• "Testing happens only at the end." Testing runs throughout the life cycle continuously.

Teacher activities

1. Starter: display a waterfall chart and an agile chart side by side and ask which suits a school assignment.
2. Define the software development life cycle and state the eight phases in order.
3. Compare waterfall and agile on flexibility and documentation.
4. Explain the testing phase and its relation to verification and validation.
5. Draw a simple waterfall lifecycle chart on the board.
6. Close with the model-choice task and exit question.

Student activities

1. Choose the starter item and explain the preference reason.
2. Define the software development life cycle in their own words and list the eight phases.
3. Compare waterfall and agile on flexibility and documentation.
4. Explain the testing phase and relate it to verification and validation.
5. Draw a waterfall lifecycle chart showing all eight phases.
6. Choose the model suited to a small team project and justify it.
7. Answer the exit question in one sentence about waterfall revisits.

Practical / learning evidence

An eight-phase waterfall chart, a waterfall versus agile comparison and a one-paragraph testing explanation. Submit all three for marking.

Resources and preparation

Printed chart templates, blank comparison sheets and sample project scenarios. Offline route: paper versions, no device needed. Display diagrams carefully and avoid touching any hardware used in demos.

Assessment for learning

Inspect the waterfall chart for eight distinct phases in order. Mark the waterfall versus agile comparison for equal criteria. Check the testing explanation for verification and validation linkage. Flag any learner who claims waterfall never revisits earlier phases.

Inclusion and homework

Provide the chart prefilled for learners who need scaffolding and allow oral comparison. Extend confident learners with seven more phases and a seven-scenario comparison. Homework: describe one real application built with the waterfall model in one paragraph.