65 coding words

Coding glossary: from algorithm to variable.

Programmers use words that sound strange at first. Here they are in plain English, with links to games and lessons.

A

Algorithm: A step-by-step set of instructions for solving a problem. A recipe is an algorithm for cooking. Learn more →
Argument: A value you give to a function when you call it. In print(5), 5 is the argument.
Array: Another name for a list in many languages: items stored in order and found by their position.

B

Binary: The number system computers use, with only 0 and 1. Each place is worth twice the one to its right. Learn more →
Bit: One binary digit, a 0 or a 1. Eight bits make a byte.
Boolean: A value that is either True or False. Conditions in an if statement are booleans.
Branch: A choice in a program. An if statement creates a branch: one path runs if the condition is true, another if it is not.
Bug: A mistake in a program that makes it do the wrong thing. Finding and fixing bugs is called debugging.
Byte: A group of eight bits. One byte can store a number from 0 to 255, or one letter.

C

Call: To run a function. greet("Sam") calls the function greet.
Class: A blueprint for making objects that bundle data with the code that works on it. Used in object-oriented programming.
Code: The instructions you write for a computer, in a programming language.
Comment: A note in your code that the computer ignores. In Python it starts with #.
Compiler: A program that translates the whole of a program into machine code before it runs.
Condition: A question the program asks that has a True or False answer, such as age > 12.
Constant: A value that does not change while the program runs. By convention it is written in capital letters.
CSS: Cascading Style Sheets: the code that styles a web page, with colours, fonts and layout. Learn more →

D

Data: Information a program stores or works on: numbers, text, lists and more.
Data type: The kind of value something is: whole number (int), decimal (float), text (str), True/False (bool) and so on.
Debugging: Finding and fixing the bugs in a program. Learn more →
Dictionary: A collection that stores pairs of a key and a value, so you can look up a value by its key.

F

Float: A number with a decimal point, such as 3.14.
For loop: A loop that repeats once for each item in a group, such as each number in a range or each letter in a word.
Function: A named block of code that does one job and can be used again and again. It can take inputs and give back an output.

H

HTML: HyperText Markup Language: the code that gives a web page its structure, such as headings, paragraphs and links. Learn more →

I

If statement: Code that runs only when a condition is true.
Immutable: Cannot be changed after it is made. Strings and tuples in Python are immutable.
Import: Bringing code from a module into your program, such as import math.
Indentation: The spaces at the start of a line. In Python, indentation shows which lines belong inside a loop, a function or an if.
Index: The position of an item in a list or string. In Python, counting starts at 0.
Infinite loop: A loop that never stops, usually because its condition never becomes false. A bug to avoid.
Input: Information that goes into a program, from the keyboard, a file or a sensor.
Integer (int): A whole number with no decimal part, such as 7 or -3.
Interpreter: A program that reads your code and runs it line by line. Python is usually run with an interpreter.
Iteration: One round of a loop, or the idea of repeating something.

J

JavaScript: The programming language that makes web pages interactive. It runs in your browser.

K

Key: The label in a dictionary that you use to find a value.

L

Library: A collection of ready-made code you can use in your own programs.
List: An ordered collection of items that you can change, written in square brackets.
Logic gate: A tiny part of a circuit that takes bits in and gives a bit out, such as AND, OR and NOT. Learn more →
Loop: Code that repeats. The two main kinds are for loops and while loops.

M

Method: A function that belongs to an object, called with a dot, such as name.upper().
Module: A file of code that you can import to use its functions.

N

Nested: Placed inside something of the same kind, such as a loop inside a loop or an if inside an if.

O

Object: A thing in a program that bundles data and the actions that can be done with it.
Operator: A symbol that does something with values, such as +, -, *, / and ==.
Output: What a program produces: text on the screen, a sound, a file.

P

Parameter: A name in a function's definition that stands for a value the function will receive.
Pixel: One tiny dot of colour on a screen. Pictures are grids of pixels.
Print: To show text or values on the screen, using the print function.
Program: A set of instructions that a computer follows.
Pseudocode: A plan for a program written in plain language rather than in a programming language.
Python: A popular, readable programming language that is a good first language for beginners. Learn more →

R

Range: A sequence of numbers made with range(), often used in loops.
Recursion: When a function calls itself to solve a smaller version of the same problem.
Return: To send a value back from a function to the code that called it.

S

Scratch: A visual programming language where you snap blocks together, used to teach children the ideas of coding.
Sequence: Instructions that run one after another in order. Sequence, selection and iteration are the three building blocks of programs.
Set: A collection that keeps each value only once, with no particular order.
Sorting: Putting items in order, for example numbers from smallest to largest. Learn more →
String: Text in a program, written in quotes.
Syntax: The rules for how code must be written, like the grammar of a programming language. A syntax error means the rules were broken.

T

Tuple: An ordered collection like a list that cannot be changed once it is made.

V

Variable: A name that stores a value so you can use it later.

W

While loop: A loop that repeats as long as a condition is true.

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