Programming Fundamentals

What is the difference between compiled and interpreted languages?

Compiled languages are translated into machine code before execution; interpreted languages are executed line-by-line at runtime.

What is a variable and why do we use it?

A variable is named storage for data, used to hold and manipulate values in a program.

What’s the difference between == and === in JavaScript?

== allows type coercion; === requires both the type and the value to match.

What is a data type?

A data type describes the kind of value a variable can hold, such as string, number, or boolean.

What is the difference between null and undefined?

null is an intentionally empty value; undefined means a variable has been declared but not assigned.

What’s the difference between stack and heap memory?

The stack stores function calls and local variables; the heap stores dynamically allocated objects.

What does it mean when a language is statically typed?

Types are checked at compile time, and variables must have known, declared types.

What does it mean when a language is dynamically typed?

Types are checked at runtime, and variables can change type while the program is running.

What is a strongly typed language?

A strongly typed language enforces strict type rules and avoids unexpected implicit type conversions.

What is a weakly typed language?

A weakly typed language performs automatic type conversions even when they may be surprising or unintended.

What is type coercion?

Automatic conversion of one data type into another, often done in weakly typed languages.

What is a constant?

A constant is a variable that cannot be reassigned after its initial value is set.

What is a literal?

A literal is a fixed value written directly in code, such as "hello" or 42.

What is an expression?

An expression is code that evaluates to a value, such as a + b.

What is a statement?

A statement is a complete instruction executed by a program, like let x = 10;.

What is a keyword in programming?

A reserved word with special meaning in a language, such as if, return, or class.

What is a syntax error?

A mistake in the structure of code that prevents it from running, like unmatched brackets.

What is a runtime error?

An error that occurs while a program is running, such as accessing an undefined variable.

What is a semantic error?

A mistake where the program runs but does not behave as intended.

What is a comment?

Text included in the code for humans to read; it is ignored by the computer.

What are operators in programming?

Symbols that perform actions on values, such as +, -, *, /, or &&.

What is type casting?

Manually converting a value from one type to another.

What is immutability?

A property where a value cannot be changed after it is created.

What is an exception?

An event that represents an error or unexpected condition during program execution.

What is exception handling?

Code that catches and responds to exceptions so a program can recover instead of crashing.

What is a library?

A collection of prewritten functions or utilities that can be reused in programs.

What is a framework?

A structured environment that provides tools, patterns, and rules for building applications.

What is an IDE?

An Integrated Development Environment — software that provides tools like editing, debugging, and building.