LESSON 1 SESSON 1 Computational Thinking and Programming Logic (COMPUTING)

Hinzugefügt: 2026-05-25

[00:00:01]Welcome back everyone.

[00:00:04]Today we are going to take a deep look at the program development cycle also known as the software development life cycle or SDLC.

[00:00:22]This week we are going to explore each stage in detail with worked examples.

[00:00:32]Have your exercise book ready. Let's go.

[00:00:46]By the end of this session, you'll be able to define the software development life cycle to bracket SDLC and explain its purpose.

[00:01:02]describe what happens at the analysis stage and produce a functional requirements.

[00:01:14]Then describe what happens at the design stage and produce a design for a given problem.

[00:01:24]Then describe what happens at the implementation stage and identify types of errors and then apply the SDLC stages to a real life Ghanaian problem.

[00:01:46]Let's do a quick recap of week 13.

[00:01:50]We learned about algorithms.

[00:01:53]That's a stepbystep instructions to solve a problem.

[00:01:58]Pseudo code algorithm written in plain English and flowcharts which is visual representation of an algorithm.

[00:02:18]The software development life cycle or SDLC is a systematic process used by software development teams to design, develop and test software.

[00:02:36]Its goal is to produce high quality software that meets the client's needs at the lowest cost in the shortest possible time.

[00:02:53]The whole process begins when a client that's the person or organization who needs the software gives the development team a problem.

[00:03:09]Gives the development team a problem specification.

[00:03:17]This is a description of what they need.

[00:03:21]the software to do.

[00:03:29]Now look at the table on your screen.

[00:03:32]There are five stages.

[00:03:34]Analysis, design, implementation, testing and maintenance.

[00:03:45]Stage one is analysis.

[00:03:48]This is where a member of the development team, usually called a systems analyst, communicates with a client to understand the problem.

[00:04:04]Three things are established at this stage.

[00:04:09]First, the purpose.

[00:04:13]What would the program be used for?

[00:04:18]Second, the functional requirements.

[00:04:23]What are the inputs, processes, and outputs?

[00:04:31]You recognize this as the IPO framework from week 13.

[00:04:39]Third, the assumptions.

[00:04:44]What conditions are assumed to be true?

[00:04:49]For example, if a program asks for a person's age, an assumption might be might be that the user will always enter a valid number.

[00:05:09]The functional requirements are recorded in a table with three columns.

[00:05:18]Inputs, processes, and outputs.

[00:05:32]Let's look at a worked example for the analysis stage.

[00:05:38]The problem specification is write a program to output the product of three numbers imputed by the user.

[00:05:51]First we write the purpose a clear description of what the program will do.

[00:06:01]Then we complete the functional requirements table.

[00:06:08]The inputs are three numbers.

[00:06:11]The process is multiplying the three numbers.

[00:06:16]The output is the product.

[00:06:20]Finally, we state our assumptions that all numbers entered will be valid numbers.

[00:06:34]Notice how clear and precise this is.

[00:06:40]The analysis stage sets the foundation for everything that follows.

[00:06:54]Now let's apply the analysis stage to Kofi and Ausius problem.

[00:07:01]The problem specification is coffee wants to write a program that calculates the total revenue from selling one item.

[00:07:14]Look at the functional requirements table on your screen.

[00:07:19]We have three inputs.

[00:07:22]Item name, price per unit, and unit sold.

[00:07:31]The process is calculating total revenue by multiplying price per unit by units sold.

[00:07:42]The outputs are the item name and the total revenue.

[00:07:52]And we state two assumptions.

[00:07:57]What the price will always that the price will always be a positive number and that the units sold will always be a whole number greater than zero.

[00:08:19]This is a complete analysis stage document.

[00:08:25]Here is your first pause and try.

[00:08:34]Pause the video now.

[00:08:37]Complete the analysis stage for this problem.

[00:08:41]A program is needed to calculate the output.

[00:08:46]Sorry, a a program is needed to calculate and output the area of a circle.

[00:08:56]The user enters the radius in centm and pi is taken as 3.14.

[00:09:06]Write the purpose.

[00:09:09]Complete the functional requirements table and state at least one assumption.

[00:09:17]Use the work example on the previous slides to guide you.

[00:09:23]Pause now and press play when you are ready.

[00:09:32]Welcome back.

[00:09:34]Here is the sample answer.

[00:09:37]The purpose clearly describes what the program does.

[00:09:42]The functional requirements table has one input radius one process area equals 3.14 multiplied by radius squared and one output area. The assumption state that the radius will be positive and that pi is taken as 3.14.

[00:10:13]How did yours compare?

[00:10:17]If your word is slightly different but the logic is the same, that's perfectly fine.

[00:10:28]The key is that the purpose is clear.

[00:10:34]The table is complete and the assumptions are stated.

[00:10:45]Stay two is design.

[00:10:50]Using everything established at the analysis stage, programmers now plan how to build the software.

[00:10:59]Three things are produced at the design stage.

[00:11:03]First, an algorithm written as pseudo code or drawn as a flowchart.

[00:11:16]You learn both of these in week 13.

[00:11:20]Second, a list of the variables and data types that will be needed.

[00:11:29]Third, a user interface design, often shown as wireframe.

[00:11:38]A wireframe is a simple sketch of what the user will see on screen.

[00:11:45]The key principle of the design stage is this.

[00:11:51]Design comes before coding.

[00:11:56]Never write code without a plan.

[00:12:06]Look at the wireframe on your screen. It shows a simple input form.

[00:12:13]This is drawn before any code is written.

[00:12:20]Let's look at the design stage for Kofi's program.

[00:12:25]First the algorithm written in pseudo code.

[00:12:31]We enter the item name, price per unit and unit sold.

[00:12:37]We calculate total revenue by multiplying price per unit by unit sold.

[00:12:45]Then we output both the item name and the total revenue.

[00:12:52]Second, the variables list.

[00:12:57]Notice that we now specify the data type for each variable.

[00:13:05]Item name is a string that means text.

[00:13:12]Price per unit is a float that means a decimal number.

[00:13:20]Unit sold is an integer, a whole number and total revenue is also a float.

[00:13:32]Specifying data types is an important part of the design stage.

[00:13:41]It helps the programmer when they move to the implementation stage.

[00:13:58]Stage three is implementation.

[00:14:01]This is where the algorithm is translated into actual code using a programming language.

[00:14:09]In this course, we use Python which we will study in detail in weeks 19 and 20. During coding, debugging may be required.

[00:14:24]This means finding and fixing errors in the code.

[00:14:30]There are three types of errors you need to know.

[00:14:37]A syntax error is a mistake in the spelling or a grammar of the code like writing prompts instead of print.

[00:14:55]A runtime a runtime error occurs when the program crashes during execution.

[00:15:04]For example, if the program tries to divide by zero, a logic error is when the program runs without crashing but gives the wrong answer. For example, using the wrong formula to calculate the area of a circle.

[00:15:31]All three types of errors can be found and fixed during implementation stage.

[00:15:45]Look at example on your screen. Figure 14.3.

[00:15:51]A correct program and the program with a syntax error each with corresponding outputs. Here is your second pause and try. Pause the video now. Study the pseudo code for Kofi's circle area program.

[00:16:15]Answer the three questions.

[00:16:18]First, what type of error is present?

[00:16:24]Second, what is the correct formula?

[00:16:28]Rewrite step two correctly.

[00:16:31]Third, complete the design stage by writing the variables list for this program.

[00:16:43]Think carefully about the error type.

[00:16:48]Is it a syntax error, a runtime error, or a a logic error?

[00:16:58]Pause now and press play when you are ready.

[00:17:09]Welcome back.

[00:17:12]Here are the answers. Here are the answers.

[00:17:16]The error in the pseudo code is a logic error.

[00:17:22]The program would run without crashing but it would give the wrong answer because addition was used instead of multiplication.

[00:17:33]The correct formula is 3.14 multiplied by radius multiplied by radius.

[00:17:41]The correct step is let area = 3.14 * radius * radius.

[00:17:51]For the variables list, we have two variables radius and area both of data type floats because they can be decimal numbers.

[00:18:10]Did you identify the error type correctly?

[00:18:15]The distinction between syntax, runtime, and logic errors is important.

[00:18:24]Make sure you understand all three.

[00:18:33]Here's your challenge tax for session one. Pause the video.

[00:18:38]Complete the full analysis and design stages for this problem.

[00:18:46]A program is required to calculate a wall area of a room given its length, breadth and height.

[00:18:58]I have given you the formula as a hint.

[00:19:03]Your response should include a purpose statement, a functional requirements table, at least one assumption, a pseudo code algorithm, and a variables list with data types.

[00:19:30]This brings together everything from today's session.

[00:19:39]Pause now and press play when you are ready.

[00:19:56]Here's the full answer.

[00:20:01]The purpose clearly describes the program.

[00:20:06]The functional requirements table has three inputs, one process and one output.

[00:20:14]The assumption states that all measurements will be positive numbers.

[00:20:20]The pseudo code follows the IPO structure.

[00:20:26]Three inputs, one process, one output.

[00:20:32]And the variables list has four variables.

[00:20:39]All of data type floats because they can be decimal numbers.

[00:20:47]If you completed all five parts correctly, excellent work.

[00:20:56]If you missed any part, review it carefully before session two.

[00:21:12]Excellent work today.

[00:21:14]Let's recap what we covered.

[00:21:18]The analysis stage produces a purpose statement, a functional requirements table, and assumptions.

[00:21:29]The design stage produces a pseudo code algorithm, variables list, and a wireframe.

[00:21:40]The implementation stage is where code is written and errors are debugged.

[00:21:49]And we learn three types of errors.

[00:21:53]Syntax, runtime, and logic.

[00:21:59]Use the selfch check on your screen.

[00:22:05]For your take-home task, complete the full analysis and design stages for the students average mark problem.

[00:22:23]We will build on this in session two when we cover testing and maintenance.

[00:22:34]See you there.

[00:22:46]Thank you.

[00:22:48]Have a great day. Bye-bye.