Junior Programmer key terms

A named storage location in a program that holds a value which can change while the program runs. Its name lets later code read or update that stored value.

A classification that tells the language what kind of value a variable holds, such as whole number, decimal number, text, or true/false, and which operations are allowed on it.

A symbol or keyword that performs an operation on one or more values, for example addition, comparison, or logical AND. Operators combine values into expressions that produce a result.

A combination of values, variables, and operators that the language evaluates to produce a single result. For example, a calculation or comparison written in code is an expression.

The set of grammar rules defining how statements and expressions must be written in a programming language. Code that breaks these rules fails to compile or parse, even if the logic is correct.

Changing a value from one data type to another, either automatically by the language or explicitly by the programmer. Converting text to a number, for example, may fail or lose precision.

A data type with only two possible values, true and false. Boolean expressions drive decisions in conditionals and loops, and comparison operators produce boolean results.

A control structure that runs one block of code or another depending on whether a condition evaluates to true or false. If, else, and switch are common examples.

A control structure that repeats a block of code while a condition holds or for a fixed number of times. Loops avoid duplicating the same statements many times.

One pass through the body of a loop, or the process of visiting each element of a collection in turn. Iteration is how programs process every item in a list.

A loop whose exit condition never becomes false, so it repeats forever and the program appears to freeze. It usually results from a missing or incorrect update inside the loop body.

A named, reusable block of code that performs a task and may accept inputs and return a result. Functions let programmers break a large program into smaller, testable pieces.

A named input declared in a function's definition that receives a value when the function is called. Arguments are the actual values supplied by the caller for those parameters.

The result a function sends back to the code that called it, ending the function's execution. A function without an explicit return value typically gives back nothing or a default like null.

The region of a program where a variable or function name is visible and usable. Local variables are visible only inside their block, while global ones are visible across the file.

A separate source file or unit of code that groups related functions, classes, and values. Modules are imported by other code, which keeps large programs organized and avoids name clashes.

An ordered collection of elements stored under one name and accessed by a numeric position, usually starting at zero. Arrays hold many values of the same type in a fixed order.

The numeric position used to read or change an element in an array or list. In most languages the first element has index zero, and using an invalid index causes an error.

A collection that stores key-value pairs, allowing a value to be looked up quickly by its unique key rather than by a numeric position. Keys are usually strings or numbers.

A sequence of characters used to represent text. Strings can be measured, sliced, joined, and searched, and many languages treat them as immutable, meaning changes create a new string.

Joining two or more strings end to end to form a single new string. Many languages use a plus sign or a dedicated function for this operation.

A blueprint that defines the attributes and methods its objects will have. Writing a class does not create an object; it describes what objects of that type contain and can do.

A concrete instance created from a class, holding its own values for the class's attributes. Multiple objects can be made from one class and each keeps separate state.

A data field that belongs to an object or class and stores part of its state, such as a name or balance. Attributes are read and changed through the object.

A function defined inside a class that describes something its objects can do or an action on their data. Methods are called on an object and can access its attributes.

A relationship where one class derives from another and reuses its attributes and methods, adding or overriding behavior. The child class extends the parent class and is a more specialized type.

An event that interrupts normal execution because something went wrong, such as a missing file or invalid input. Exceptions can be caught and handled so the program does not crash.

A structure that runs risky code in a protected block and handles any exception it raises in a separate block, preventing an abrupt crash. Finally blocks can run cleanup code regardless of success.

The process of finding and fixing defects in a program by reproducing the problem, inspecting state, and testing a correction. Breakpoints and step-through execution are common debugging techniques.

An automated test that checks one small piece of code, usually a single function, against expected outputs. Unit tests are run often to catch regressions when code changes.

Reading from or writing to files on disk using a program, typically by opening a file, performing operations, then closing it to release resources and save changes.

The collection of prewritten modules and functions that ships with a programming language, offering ready-made tools for strings, files, math, and networking so programmers need not build everything.

A search that checks each element of a collection one by one until the target is found or the end is reached. It works on unsorted data but can be slow for large collections.

A fast search that repeatedly halves a sorted collection by comparing the target with the middle element. It requires sorted input and takes about log n comparisons for n elements.

Arranging the elements of a collection into a defined order, such as ascending numbers or alphabetical text. Efficient sorting makes searching faster and output easier to read.

A way to describe how an algorithm's running time or memory use grows as input size increases, ignoring constants. For example, O(n) means work grows in proportion to the input.

A system that records changes to files over time so programmers can review history, restore earlier versions, and collaborate. Git is the most widely used version control tool.

A saved snapshot in version control that records a set of changes together with a message and author information. Commits form the history you can inspect, compare, or revert to.

The storage location that holds a project's files and its complete version history. It can live locally on a computer or remotely on a hosting service for sharing.

An integrated development environment, a single application that combines a code editor, compiler or interpreter, debugger, and other tools to make writing and testing programs easier.