C++ Identifiers

C++ identifiers are the name assigned to a function, variable, or any other user-defined item. They are the basic requirement of any language. Identifiers can be from one to several characters long.

In short, we can say that the C++ identifiers represent the essential elements in a program which are given below:

• Constants
• Variables
• Functions
• Labels
• Defined data types

Some naming rules are common in both C and C++. They are as follows:

• Variable names can start with any letter of the alphabet or an underscore.
• The identifier name cannot start with a digit, i.e., the first letter should be alphabetical. After the first letter, we can use letters, digits, or underscores. The underscore can be used to enhance the readability of a variable name, as in line_count.
• Uppercase and lowercase are seen as different; that is, to C++, myvar and MyVar are separate names. So, we can say that C++ identifiers are case-sensitive.
• A declared keyword cannot be used as a variable name. In addition, predefined identifiers such as cout are also off limits.

Below are some guidelines for working with identifiers

• Identifier names should be long enough to be descriptive.
• The length of a variable’s name should be proportional to its scope.
• Avoid cryptic abbreviations and give proper spelling for identifiers.
• Short names (x, b, y, and so on) should be used only where their brevity makes the code more readable and where the usage is so obvious that a descriptive name is not needed.
• Make sure identifiers look and sound different from one another to minimize confusion.
• Function (or method) names should be usually like verbs or verb-noun phrases. For example search(), reset(), findParagraph(), showCursor().
• Variable names are usually abstract nouns, possibly with an additional noun: count, state, windSpeed, windowHeight.
• Boolean variables should be named appropriately. Eg: windowIconized, fileIsOpen.

When creating your own style spelling and capitalization should not be overlooked .

Below are some tips for these areas include the following.

enum TextStyle
{
tsPlain,
tsBold,
tsItalic,
tsUnderscore,
};

Valid Identifiers

The following are the examples of valid identifiers are:

Result
Test2
_sum
power

Invalid Identifiers

The following are the examples of invalid identifiers.

Sum-1   // containing special character '-'.
2data    // the first letter is a digit. 
break    // use of a keyword.

Below table shows the valid and invalid identifiers.

The major difference between C and C++ is the limit on the length of the name of the variable. ANSI C considers only the first 32 characters in a name while ANSI C++ imposes no limit on the length of the name.

The following is the list of differences between identifiers and keywords.