Keywords in C
Keywords are predefined or reserved words that have special meanings to the compiler. These are part of the syntax and cannot be used as identifiers in the program. A list of keywords in C or reserved words in the C programming language are mentioned below:
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 |
We cannot use these keywords as identifiers (such as variable names, function names, or struct names). The compiler will throw an error if we try to do so.
Example:
#include <stdio.h>
int main() {
int return = 10;
printf("%d\n", return);
return 0;
}
Output
./Solution.c: In function 'main':
./Solution.c:4:9: error: expected identifier or '(' before 'return'
int return = 10;
^
./Solution.c:5:20: error: expected expression before 'return'
printf("%d\n", return);
^
Let's categorize all keywords based on context for a more clear understanding.
| Category | Keywords |
|---|---|
Data Type Keywords | char, int, float, double, void, short, long, signed, unsigned |
| Operator & Utility Keywords | |
Control Flow Keywords | if, else, switch, case, default, for, while, do, break, continue |
| Storage Class Keywords | auto, register, static, extern |
| Type Qualifiers | const, volatile |
| User Defined Types | struct, union, enum |
Difference Between Keywords and Identifiers
| Keywords | Identifiers |
|---|---|
| Reserved Words in C that have a specific meaning and use in the syntax | Names given to variables, functions, structs, etc. |
| Cannot be used as variable names. | Can be used as variable names (if not a keyword). |
| Examples: int, return, if, while | Examples: x, total, count |
| Part of the C language grammar. | User-defined, meaningful names in the code. |
| Cannot be redefined or repurposed. | Can be defined redefined and reused as needed. |
