The development life cycle and design tools
Building a program
- A program is built in stages — the program development life cycle.
- We plan it with design tools, then write the algorithm.
- Every algorithm breaks into input → processing → output.
The four stages
- Analysis — study the problem and work out what's needed.
- Design — plan how the program will work.
- Coding — write the code, testing small parts as you go (iterative testing).
- Testing — run the finished program with test data to find errors.
- Two analysis skills: abstraction (keep only the important details) and decomposition (break a big problem into smaller parts).
Practice
Put the development life cycle stages in order.
Analysis (what is needed) → design (plan) → coding (write) → testing (check).
Practice
Abstraction means:
Abstraction simplifies; decomposition breaks a problem into parts.
Practice
Decomposition means:
Decomposition splits a large problem into manageable sub-problems.
Design tools
- A structure diagram — shows the parts of a system and how they fit together.
- A flowchart — boxes and arrows showing the steps in order.
- Pseudocode — steps in simple, code-like English (not a real language).
Practice
Pseudocode is:
Pseudocode describes an algorithm in readable, code-like English without being a real language.
Input, processing, output
- Every algorithm decomposes into input (the data in), processing (the work done), and output (the result).
- e.g. "average of three marks": input the 3 marks → add them and divide by 3 → output the average.
Practice
Every algorithm can be decomposed into:
Input (data in) → processing (the work) → output (the result).
You've got it
Key idea
- life cycle: analysis → design → coding → testing
- abstraction = keep what matters; decomposition = break into parts
- design tools: structure diagram, flowchart, pseudocode
- every algorithm = input → processing → output