Table of Contents
In this lesson, you will learn about Keywords and identifiers in C. Keywords, or reserved words, are used in the C language as part of the syntax. Identifiers are the names in a C program, such as variables, functions, constants, arrays, etc.
C Keywords
In C, there are keywords or reserved words that are part of the program for a purpose, such as the ‘if’ keywords, which he used for an ‘if’ condition statements. Generally, there are 32 keywords; these keywords cannot be utilized to name a function, a variable, an array, etc.
List of Keywords in C
Below are all the Keywords in C, listed in alphabetical order.
| auto | break | case | char |
| const | continue | default | do |
| double | else | enum | extern |
| float | for | goto | if |
| int | long | register | return |
| short | signed | sizeof | static |
| struct | switch | typedef | union |
| unsigned | void | volatile | while |
Keywords in C and their Usage
auto, signed, const, extern, register, unsigned – used to define a variable.
break – used to break out a loop or case statement.
continue – used to perform the next iteration in ‘for’, ‘white’, and ‘do-while loops, skipping the rest of the current iteration statements.
enum – used to define an enumerator.
for, while, do – used to define loops.
goto– used to jump to a specific statement in the code.
if, else, switch, case, default – Used for decision control.
int, float, char, double, long – datatypes that are used during variable or function declaration.
return – used to return a value.
sizeof – used to know the size of an object.
struct, typedef – used in structures
union – used to define a collection of variables that share the same memory location and memory storage.
void – to define a function as a void function.
volatile – Volatile tells the compiler not to optimize anything associated with a volatile variable
C Identifiers
Identifiers in C are the name that programmers come up with for variables, functions, arrays, etc. They are a collection of alphanumeric strings that must begin with an alphabet or an underscore. For Example, Students, _Students, are valid identifiers in C.
Type of Identifiers in C
In the C Programming language, there are two types of identifiers.
- Internal identifier
- External identifier
Internal Identifier: An internal Identifier type is used within a class or function scope and cannot be used in the external linkage. An example of an Internal Identifier is a local variable.
External Identifier: An External Identifier is used for external linkage, suck as global variables, and public functions.
Rules of identifiers in C
- Identifiers are case sensitive; for example, the identifiers var1 and Var1 are not the same.
- Identifiers can be constructed with upper or lowercase alphabetic characters and can contain numbers (0 to 9), the dollar sign ($), and the underscore (_)
- blank space of commas cannot be part of identifiers.
- Identifiers cannot begin with a number.
- Identifiers cannot be the same as a keyword. For Example, ‘short’ cannot be used as an identifier.
- identifiers cannot be more than 31 characters in length
- Use the camelCase or PascalCase naming convention for better readability.
Good naming Convention: StudentRecords. customerOrder
bad naming convention: Studentrecord, cutomerorder
Now we have learned about Keywords and Identifiers, Let’s move to the next lesson!