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Keywords in C++
In C++, keywords are predefined reserved identifiers that hold specific meanings and cannot be utilized as identifiers in our program. C++ reserves a set of keywords for its own use.
C++ allocates a collection of words for specialized purposes, often referred to as reserved words. In the table below, certain keywords are outlined, emphasizing that they cannot be employed in a program as variables or identifiers. If any attempt is made to use these reserved words mistakenly, the compiler will generate an error.
| KEYWORDS | DESCRIPTION |
|---|---|
| asm: | Allows insertion of assembly language commands directly into code. |
| auto: | Directs the compiler to deduce the type of a declared variable from its initialization expression. |
| bool: | Represents a variable with two values: True and False. |
| break: | Ends the execution of the nearest enclosing loop or conditional statement. |
| case: | Used in a switch statement to test a variable against a list of values. |
| catch: | Indicates the catching of an exception in a program. |
| char: | Represents a data type for single characters. |
| class: | A blueprint for a user-defined data type. |
| const: | Declares a constant in C++. |
| const_cast: | Used to cast away the constness of variables. |
| continue: | Skips the code in between and forces the next iteration of a loop to take place. |
| default: | Optional case in a switch statement for tasks when none of the cases is true. |
| delete: | Used to delete dynamically allocated memory. |
| double: | Allocates memory for floating-point numbers. |
| do: | Represents a do...while loop that tests the condition at the bottom of the loop. |
| dynamic_cast: | Converts pointers from parent to child types. |
| else: | Optional clause in an if statement executed when the Boolean expression is false. |
| enum: | Creates enumerations for a new, simple type. |
| explicit: | Specifies whether user-defined type conversions are explicit or implicit. |
| export: | Marks a template definition as exported. |
Note:
In C++ programming, it's essential to recognize that keywords are case-sensitive. This means that the compiler distinguishes between uppercase and lowercase letters when interpreting the language's reserved words. For instance, "if," "If," and "IF" are treated as distinct keywords.
| KEYWORDS | DESCRIPTION |
|---|---|
| extern: | Gives a reference of a global variable visible to all program files. |
| false: | Represents one of the two values for a bool type. |
| float: | Stores real numbers or floating-point numbers. |
| for: | Repetition control structure for efficiently writing loops. |
| friend: | A function that can access non-public members of a class. |
| goto: | Allows the program's execution flow to jump to a specified location within the function. |
| if: | A conditional statement with an optional else clause. |
| inline: | Creates an inline function. |
| int: | Stores integer values. |
| long: | Represents a data type that may occupy more storage than int. |
| mutable: | Allows a member of an object to override const member functions. |
| namespace: | Mechanism for grouping features in a program. |
| new: | Allocates memory dynamically for any data type. |
| operator: | A symbol that tells the compiler to perform specific manipulations. |
| private: | A member variable or function inaccessible from outside the class. |
| protected: | Similar to private but can be accessed in derived classes. |
| public: | Accessible from anywhere outside the class within a program. |
| register: | Defines local variables stored in a register instead of RAM. |
Note:
In C++ programming, the case sensitivity applies not only to keywords but also to identifiers—names given to variables, functions, classes, and other user-defined entities. Therefore, "MyVariable" and "myvariable" would be considered two separate identifiers in C++.
| KEYWORDS | DESCRIPTION |
|---|---|
| reinterpret_cast: | Converts a pointer to a new designated type. |
| return: | Used to return values from a program or function. |
| short: | Represents integers that may occupy fewer bytes of memory than int. |
| signed: | A data type that can be int or char, with positive, negative, or zero values. |
| sizeof: | Computes the amount of memory in bytes. |
| static: | Keeps a local variable in existence during the program's lifetime. |
| static_cast: | Performs narrowing conversion and silences compiler warnings. |
| struct: | Similar to class but with default public access to members. |
| switch: | Allows testing a variable for equality against a list of values. |
| template: | Enables defining a family of functions or classes operating on different types. |
| this: | A pointer giving every object access to its own address. |
| throw: | Used to throw exceptions when a problem occurs. |
| true: | Represents one of the two values for a bool type. |
| try: | Identifies a block of code for which exceptions will be caught. |
| typedef: | Creates a new name for an existing type. |
| typeid: | Returns information about an object's data type. |
| typename: | Replaces class in a template definition in some C++ compilers. |
| union: | Defines a single location with many different field names. |
| unsigned: | A data type that can be int or char, always positive or zero. |
| using: | Informs the compiler that the subsequent code is using names in the specified namespace. |
| virtual: | Used to create virtual functions in a base class. |
| void: | Represents the absence of any data type, returning no value to the program. |
| volatile: | Informs the compiler that a variable's value may change in unspecified ways. |
| wchar_t: | Represents wide characters. |
| while: | Represents a do...while loop that tests the condition at the bottom of the loop. |
A C++ identifier serves as a designation for a variable, function, class, module, or any other user-defined element. It commences with a letter from A to Z or a to z, or an underscore (_), followed by zero or more letters, underscores, and digits (0 to 9).
In C++, the use of punctuation characters such as @, $, and % within identifiers is not permitted.
While mathematicians may find single-letter names like x sufficient for their variables, programmers are encouraged to adopt longer, more descriptive variable names. For instance, names such as altitude, sum, and User_name are preferable to the more concise but less informative options like a, s, and u. A variable's name should convey its purpose within the program, contributing to enhanced readability for human understanding.
As mentioned earlier, within C++ programming, identifiers, which are the names assigned to variables, functions, classes, and other user-defined entities, exhibit case sensitivity. Consequently, in C++, "MyVariable" and "myvariable" are recognized as distinct identifiers.
C++ has some important rules for naming variables. It's essential to understand these basic rules before you create any variable in C++ programming.
- An identifier must contain at least one character.
- The first character must be an alphabetic letter (upper or lower case) or an underscore.
- Subsequent characters may be alphabetic characters (upper or lower case), underscores, or digits (0 to 9).
- No other characters, including spaces, are permitted in identifiers.
- Reserved words cannot be used as identifiers.
- C++ is case-sensitive; therefore, "Temp" and "temp" are distinct identifiers.
Programmers are advised to use descriptive and meaningful variable names to enhance code readability. Following these rules ensures the proper creation of identifiers in C++ programming.
Valid Names:
AddNumbers , sum , Omar , Move_left , a_001 , totalAge, _temp, goto_number14
Invalid Names:
Sum of Numbers ( contains whitespace ), 13UserName ( starting with number ), goto ( using keywords ),
Sardar Omar
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