Thinking Like a Programmer

🗣️ Programming words

A program is a set of instructions for a computer. Source code is the program as a person writes it. Syntax is the grammar rules of a language. A bug is a mistake; debugging is finding and fixing it. An IDE (integrated development environment) is an app for writing, running and debugging code.

🪜 Levels of programming languages

Machine code is pure binary that the CPU runs directly. Assembly language uses short words (mnemonics) like ADD and MOV, one per machine instruction. High-level languages such as Python, Java, C++ and Scratch read more like English and work on many computers. These lessons use Python.

⚙️ Compilers and interpreters

The CPU only understands machine code, so high-level code must be translated. A compiler translates the whole program first, producing a file that runs fast. An interpreter translates and runs it one line at a time, which makes testing easy. Python usually runs through an interpreter.

🔄 Stages of program development

Programs are built in stages: define the problem, design a solution (the algorithm), write the code, test and debug it, put it into use, then document and maintain it. Skipping design and testing is how bugs reach users.

🧭 Algorithms, pseudocode and flowcharts

An algorithm is a step-by-step solution. A good one is clear, finite (it ends), has inputs and outputs, and every step can actually be done. Pseudocode writes it in plain structured English (START, INPUT, OUTPUT, END). Flowcharts draw it: ovals for start and end, parallelograms for input and output, rectangles for processing, diamonds for decisions.

Key points

• Source code is what programmers write; syntax is the language's grammar.
• A bug is a mistake, and debugging is fixing it.
• Machine code is binary; assembly uses short words; high-level languages read like English.
• A compiler translates everything first; an interpreter runs line by line.
• Programs are built in stages: define, design, code, test, use, maintain.
• A good algorithm is clear, finite and has inputs and outputs.
• In flowcharts, diamonds are decisions and parallelograms are input and output.

Try it for real: Design before you code

• Write pseudocode for making tea: START, list each step, END.
• Draw a flowchart for: "Input a mark. If it is 50 or more, output Pass, otherwise output Fail."