Question

Which of the following are valid \(\mathrm{C}++\) identifiers? a. firstCPPProject b. POP_QUIZ c. C++Program2 d. quiz7 e. ProgrammingLecture2 f. 3feetIn1Yard g. Mike'sFirstAttempt h. Update Grade i. 4th j. New_Student

Short answer

Valid identifiers are: a, b, d, e, j.

Step-by-step solution

Understanding Identifier Rules

Identifiers in C++ are names assigned to entities such as variables, functions, arrays, etc. The rules for valid identifiers are: 1) Identifiers can contain letters (both uppercase and lowercase), digits, and underscores ('_'); 2) They must not begin with a digit; 3) Identifiers must not be a reserved keyword in C++; 4) They cannot contain spaces or special symbols like '@', '$', or '%'; 5) Identifiers are case-sensitive.

Analyzing Identifier - 'firstCPPProject'

This identifier starts with a letter and contains only letters. It meets all the identifier rules. Therefore, 'firstCPPProject' is valid.

Analyzing Identifier - 'POP_QUIZ'

This identifier uses uppercase letters and an underscore. It does not start with a digit and follows all identifier rules. Thus, 'POP_QUIZ' is valid.

Analyzing Identifier - 'C++Program2'

This identifier contains the '+' symbol, which is not allowed in identifiers. Hence, 'C++Program2' is not valid.

Analyzing Identifier - 'quiz7'

This identifier starts with a letter and contains only letters and digits. It follows all the rules for valid identifiers. Therefore, 'quiz7' is valid.

Analyzing Identifier - 'ProgrammingLecture2'

This identifier starts with a letter and contains only letters and digits, making it valid according to the identifier rules.

Analyzing Identifier - '3feetIn1Yard'

This identifier starts with a digit, which violates the rules for identifiers. Hence, '3feetIn1Yard' is not valid.

Analyzing Identifier - "Mike'sFirstAttempt"

This identifier contains an apostrophe ('''), which is not allowed in identifiers. Thus, "Mike'sFirstAttempt" is not valid.

Analyzing Identifier - 'Update Grade'

This identifier contains a space, which is not permitted in identifiers. Therefore, 'Update Grade' is not valid.

Analyzing Identifier - '4th'

This identifier starts with a digit, which is a violation of the identifier rules. Hence, '4th' is not valid.

Analyzing Identifier - 'New_Student'

This identifier begins with a letter and includes only letters and underscores, matching all the rules for valid identifiers. 'New_Student' is valid.

Key concepts

Identifier Rules

In C++ programming, identifiers are names given to various elements such as variables, functions, and arrays. These names follow specific rules to ensure code clarity and functionality. Here are the key rules:

• Identifers can consist of letters (a-z, A-Z), digits (0-9), and underscores ('_').
• They should not begin with a digit since this would cause confusion between identifiers and numeric literals.
• Identifiers cannot include spaces or special symbols like '@', '$', or '%'.
• Apart from not starting with a digit, identifers are case-sensitive, meaning that 'Variable' and 'variable' are considered different identifiers.
• They should not be reserved keywords, which are pre-defined by C++ for specific functions.

Understanding these rules helps avoid syntax errors and ensures code proper execution.

Valid Identifiers

When assessing whether an identifier is valid in C++, it's essential to check against the identifier rules. A valid identifier adheres to the following:

• It starts with either a letter or an underscore and can be followed by a combination of letters, digits, or underscores.
• It does not incorporate spaces or special symbols beyond the underscore.
• It is unique within its scope, and identifiers should be carefully tested to confirm that they meet all these criteria.

For example, identifiers such as 'firstCPPProject', 'POP_QUIZ', 'quiz7', 'ProgrammingLecture2', and 'New_Student' conform to all the rules, qualifying them as valid. By ensuring identifiers are valid, programmers guarantee that they can correctly define and manipulate variables and other entities in their code.

C++ Programming

C++ programming is a widely-used language known for its performance and efficiency. It's an extension of the C programming language and incorporates object-oriented features. When programming in C++, understanding basics like identifiers is crucial as they are fundamental to building efficient code.

C++ uses identifiers to define variables, functions, classes, and other constructs. This enables programmers to create complex programs by breaking them down into manageable sections.

Moreover, C++ offers benefits like compatibility with the C language, access to a rich library of functions, and enhanced performance due to fine control over memory management. These features make it a popular choice for systems and applications programming. By mastering C++ identifiers and their rules, programmers can more effectively engage with the language's powerful capabilities.

Reserved Keywords

In C++, reserved keywords are specific words that have pre-defined meanings and uses within the language. They enable the language to support various operations and constructs. As a result, these words cannot be used as identifiers.

Some examples of reserved keywords include:

• int: Used to define integer variables.
• float: Used for defining floating-point variables.
• if, else: Used for conditional statements.
• for, while: Used for loops.
• return: Used to return a value from a function.

Since these keywords are integral to the language's functionality, programmers must avoid using them for naming their variables or functions. This precaution helps prevent syntax errors and ensures that the code operates as intended. When learning C++, familiarizing oneself with reserved keywords will assist in writing clear, error-free programs.