Programming Keywords Table

A reserved keyword is a word that has a special meaning to the compiler or interpreter. Because the language uses these words to define its own structure (like "if", "while", "class"), you are strictly forbidden from using them as names for your variables, functions, or classes.

You will get a Syntax Error. For example, in Python, if you try to write "class = 5", the program will crash immediately because "class" is reserved for defining objects. The compiler gets confused and stops.

Yes, in most modern languages like Python, Java, C++, and JavaScript. For example, "while" is a keyword, but "While" (capitalized) is not. However, using "While" as a variable name is considered very bad practice as it confuses other programmers.

Of the popular languages, C++ has a very large set (over 90 keywords) due to its complexity and low-level features. Python, by contrast, is designed to be simple and has only about 35 keywords. COBOL is famous for having over 300!

A contextual keyword is reserved only in specific situations. For example, in C#, "get" and "set" are keywords when defining properties, but you can use them as variable names elsewhere. This allows languages to add new features without breaking old code.

"yield" is a powerful keyword used in Generators. Instead of returning a value and exiting, a function with "yield" pauses execution and saves its state, allowing it to resume later. This is great for memory-efficient iteration.

"var" is the old way (function-scoped). "let" and "const" were added in ES6 (block-scoped) to fix common bugs. "const" creates a read-only reference, while "let" allows reassignment. You should default to "const" unless you need to change the value.

"static" means the member belongs to the CLASS itself, not to instances of the class. A static variable is shared by all objects. A static method can be called without creating an object (like Math.abs()).

In typed languages like Java and C++, "void" is used effectively as a return type to indicate that a function does NOT return a value. It performs an action and then just finishes.

No, you cannot add new keywords to a language unless you modify the compiler source code itself. However, you can write libraries or macros (in C++) that feel like language extensions.

"transient" is used in serialization. It tells the JVM to ignore this specific field when saving an object's state to a file or stream. This is useful for sensitive data like passwords that shouldn't be persisted.

"volatile" is a modifier used in multi-threaded programming. It tells the compiler that a variable's value might change unexpectedly (by another thread) and prevents the compiler from caching it, ensuring all threads see the most up-to-date value.

"goto" jumps execution deeply into another part of code without structure. This creates "Spaghetti Code" that is impossible to debug or trace. Most modern languages (like Java) reserve the word but don't even implement it to prevent its use!

An "interface" (Java) implies a contract: the class MUST implement these methods. An "abstract class" can provide some default code implementation. A class can implement multiple interfaces but only extend one abstract class.

"pass" is a null statement. It literally does nothing. It is used as a placeholder when syntax requires a statement but you don't want to write code yet (e.g., in an empty function or class definition).