Which statement(s) is/are true about formation of identifier in C? I. It consist of alphabets, digits and underscore. II. An identifier can start with an underscore.
Both I and II
Understanding C Identifier Formation Rules
Identifiers in the C programming language are names given to variables, functions, arrays, structures, unions, labels, etc. They are fundamental building blocks when writing C code. There are specific rules that must be followed when creating these identifiers to ensure they are valid.
Analyzing the Rules for C Identifiers
Let's break down the rules for forming identifiers and evaluate the given statements.
The general rules for forming identifiers in C are:
- They can consist of letters (both uppercase and lowercase,
A-Zanda-z), digits (0-9), and the underscore character (_). - The first character of an identifier must be either a letter or an underscore. It cannot be a digit.
- C identifiers are case-sensitive (e.g.,
myvariableis different fromMyVariable). - Keywords (reserved words with special meaning in C) cannot be used as identifiers.
Evaluation of Statement I: It consist of alphabets, digits and underscore.
This statement claims that a C identifier is made up of only alphabets, digits, and the underscore character. Based on the rules mentioned above, this is true. These are the only characters permitted within a C identifier.
Evaluation of Statement II: An identifier can start with an underscore.
This statement claims that a C identifier can begin with an underscore. According to the rules, the first character of an identifier must be a letter or an underscore. Therefore, starting an identifier with an underscore is indeed allowed in C.
Conclusion on C Identifier Statements
Both Statement I and Statement II accurately describe valid aspects of forming identifiers in the C programming language.
- Statement I is true because identifiers are composed exclusively of letters, digits, and underscores.
- Statement II is true because an identifier is permitted to start with an underscore.
Thus, both statements are true.
Revision Table: C Identifier Rules
| Rule Aspect | Description | Valid Example | Invalid Example |
|---|---|---|---|
| Allowed Characters | Alphabets (a-z, A-Z), Digits (0-9), Underscore (_) | my_var1 |
my-var (contains '-') |
| Starting Character | Must be a letter or an underscore | _count, data |
1variable (starts with digit) |
| Case Sensitivity | C is case-sensitive | Var and var are different |
N/A |
| Keywords | Cannot be keywords | myint |
int (is a keyword) |
Additional Information on C Identifiers
While starting an identifier with an underscore is syntactically correct, it is a common convention in C programming to avoid using identifiers that start with an underscore, especially followed by another underscore or an uppercase letter. Such names are often reserved for internal use by the C standard library and system headers. Using them might lead to name conflicts.
The length of an identifier is technically unlimited by the C standard, but compilers might have limitations on the number of significant characters. However, for practical purposes, keeping identifier names reasonably short and descriptive is good practice.
Important Questions from Programming in C
In object-oriented programming, which keyword ensures that a member variable belongs to the class itself rather than to any specific object, thereby allowing all instances to share a single copy of that variable?
The three basic structure types used to write the algorithm for a program are sequence, selection and repetition. Which of the following is NOT an advantage of using only these structures when writing the algorithm for a program?
What is the output of the code written in C?
void main()
{
printf("%d",7%-3);
printf("%d",-7%3);
}
Which of the following statement(s) is/are true about pre-processor in C/C++?
I. To replace each #include directive with the contents of the designated file.
II. To replace each escape sequence with designated character.
III. To process macro definitions and expand macro calls.
______ converts a source code to object code.
