JSS 3 First Term

Learning Objectives

• Explain what programming is and the parts of a program.
• Describe the input, process and output model.
• Write a simple program plan in pseudocode.
• Find and fix a simple error in a program.

Starter Scenario

A chief gives a driver, a chef and a market trader the same set of instructions, but each one is written in their own style. The driver needs a route, the chef needs a recipe and the trader needs a price list. Similarly, people and computers need instructions in a form they understand. Programming is writing instructions in a form a computer can follow, and the form is called a programming language.

What is Programming

Programming is the process of writing instructions for a computer to carry out. The instructions, taken together, are called a program. A program is different from an algorithm. An algorithm is a plan that anyone can understand, while a program is the same plan written in a programming language so that a computer can run it. People who write programs are called programmers, and nearly every app, game, website and device you use is built on programs.

A programming language has a fixed set of rules and words that a computer understands. Humans write in the language, and the computer translates it into the 0s and 1s it uses. Some languages use visual blocks that snap together, such as Scratch, while others use typed words, such as Python. Both describe the same ideas, just in different forms. Scratch is a good first language because you build programs from blocks, and Python is a typed language that reads almost like simple English.

The Input, Process, Output Model

Almost every program follows three parts. Input is the data that goes into the program. Process is the work the program does on that data. Output is the result the program gives back. In a calculator, the two numbers are the input, the multiplication is the process, and the displayed answer is the output. In a greeting program, the user's name is the input, joining the name to a greeting is the process, and showing the full greeting is the output.

Everyday devices follow the same model. In an ATM, the card and PIN are the input, checking the details is the process, and dispensing money or showing a message is the output. In a GPS, the current position is the input, finding the route is the process, and showing the map and directions is the output. In a music app, your search is the input, finding the song is the process, and playing the chosen song is the output. Thinking of any task in these three parts makes writing a program much clearer.

The input, process, output model maps straight onto a flowchart from Week 9. The parallelogram for input and output becomes the input and output steps, and the rectangle for process becomes the processing action. So when a learner writes a program, they first choose what data comes in, what processing happens, and what result should come out, exactly as they did with flowcharts.

Writing and Debugging a Simple Program

A simple greeting program follows the input, process, output model. It asks for a name, joins the greeting to it, and shows the result. In Scratch, you could use a block that asks the name, another that joins the words, and a block that says the result. In Python, the same idea is written as a few typed lines of code. Reading these steps aloud shows the exact order the program follows.

A program runs from top to bottom, one instruction at a time, just like a flowchart follows arrows. To predict what a program does, follow each line in order and jot down the values as you go. For a greeting that uses a name, the input of the name must come before the output uses it, otherwise the program has nothing to display. Changing the order changes the effect.

A bug is an error that stops a program from running correctly. Debugging is the process of finding that error and fixing it. Common bugs include typing a word wrongly, connecting blocks in the wrong order, using the wrong symbol, or forgetting a required part such as closing a quote. A reliable way to debug is to read the program line by line, run it to see the error message, and then compare each part with the intended steps. Fixing a bug is not failing, it is part of normal programming, and every programmer, even the most experienced, debug programs all the time.

A short program meant to greet a user instead shows nothing because it tries to display a greeting before the name has been given. The fix is to move the input step before the output step. Learners should identify the ordering error and describe the correct order, which mirrors the debugging skill used at the start of this period.

Programming Basics and Language Levels

Programming is giving a computer a clear set of instructions to follow. A program is a complete set of instructions that tells a computer how to perform a specific task. A simple program might ask for a number and then double it, while a complex program like a web browser handles millions of instructions every second.

Programming languages are grouped into levels. Machine language uses only 0s and 1s and is the only language a computer understands directly, but it is very hard for humans to read. Assembly language uses short codes such as ADD or MOV, which is easier but still tied to one type of processor. High-level languages such as Python, Scratch and Java use words close to everyday English. They must be translated into machine language before the computer can run them, but a compiler or interpreter does this automatically.

Simple Program Structures and Pseudocode

Even complex programs are built from a few simple structures. Sequence runs instructions one after another in order. Selection makes a choice, such as if the score is above 50, then say pass, otherwise say try again. Repetition repeats a group of instructions until some condition is met. Together these three structures build every app and game.

Pseudocode is a planning tool that looks like a mixture of English and program words. For example, the pseudocode for a greeting program might read ask for a name, then welcome the name, then show the message. Because pseudocode is not tied to one language, the same plan can be turned into Scratch, Python or any other language.

Programming Environments and Careers

Programs are written using an integrated development environment, often called an IDE, which gives programmers a place to type code, check for errors and run their program in one window. When a high-level program is ready, the computer translates it into machine language. Compilers translate the whole program at once into a runnable file, while interpreters translate and run the program line by line.

Programming skills open up many careers. Software developers build apps, games and office programs. Web developers create websites, and data analysts write programs that turn information into reports and charts. In Nigeria, banks, telecom companies such as MTN and Glo, and government agencies all employ programmers to build systems that serve millions of customers every day.

Practical Work

1. Write pseudocode for a program that greets a named user.
2. Describe the input, process and output of an ATM transaction.
3. Find the ordering error in a greeting program and correct it.
4. Write two differences between an algorithm and a program.

Scenario-Based Questions

1. A pupil writes a program that asks for two numbers and is supposed to add them, but it shows the product instead. Name this type of error and describe the step-by-step process the pupil should follow to find and fix it.
2. A school receptionist wants a program that asks for a visitor's name, asks whether the visitor is a parent or a staff member, and then prints a welcome message with the correct title. Write pseudocode for this program using sequence and selection.
3. A teacher says a program with an infinite loop will never stop. Give an example of an everyday task that could be written as an infinite loop and explain why it would be a problem on a computer.
4. A market trader wants a program that keeps asking for item prices until the trader types 0, then prints the total. Explain why iteration is needed here instead of just sequence, and write a short pseudocode.
5. A pupil says Scratch is a programming language but Python is not. Correct this statement by explaining what both Scratch and Python are and how they differ.
6. A student writes a program: ask for a number, if the number is greater than 10 print Big, otherwise print Small. Test the program mentally with the values 5, 10 and 15 and write the expected output for each.
7. An ATM machine follows the input-process-output model. Describe the input, the process and the output for one complete ATM transaction from insertion of the card to collection of cash.