2. Pseudocode: Writing Algorithms in Plain Steps

Pseudocode: Writing Algorithms in Plain Steps

Pseudocode is a way of writing an algorithm in short, structured English. It is not any real programming language, so the computer cannot run it — but it reads almost like code, so it is the perfect bridge between an idea in your head and a program in Python. You think in pseudocode, then translate it line by line into real code.

Why pseudocode helps

It lets you plan the logic without worrying about exact Python punctuation and spelling.
It is easy for any human to read and check.
Each pseudocode line usually becomes one line of real code, so translation is simple.

Common pseudocode keywords (conventions)

Keyword	What it means
`INPUT` / `READ`	Ask the user for a value and store it.
`SET` / `←`	Give a variable a value (assignment).
`OUTPUT` / `PRINT`	Show a value or message to the user.
`IF ... ELSE`	Make a decision; do one thing or another.
`WHILE`	Repeat steps while a condition stays true.
`FOR`	Repeat steps a fixed number of times.
`REPEAT ... UNTIL`	Repeat steps until a condition becomes true.

We indent the lines inside an IF, WHILE or FOR so it is obvious which steps belong together — exactly as Python will later force us to do.

A tiny example: greet the user by name

Problem

Ask the user for their name, then print a friendly greeting that includes it.

Pseudocode

START
  INPUT name
  SET message = "Hello, " + name
  OUTPUT message
END

In Python

name = input("What is your name? ")
message = "Hello, " + name
print(message)

Output: (if the user types Ada)

Hello, Ada

Notice how each pseudocode line turned into one Python line. That is the whole point of pseudocode: plan it in plain steps, then translate.