C Keywords - The Coding College

C programming language includes a set of reserved words known as keywords. These keywords have predefined meanings in the language and cannot be used as identifiers (e.g., variable names, function names). This article by The Coding College explains C keywords in detail, their categories, and their usage with examples to help you master C programming.

What Are C Keywords?

Keywords in C are reserved words that are part of the language syntax. They are used to perform specific operations and control the flow of the program. C has 32 keywords defined in its standard, which are case-sensitive and written in lowercase.

List of C Keywords

Here’s a categorized list of all C keywords:

Data Types

char
double
float
int
void

Control Statements

if
else
switch
case
default

Loops

for
while
do
break
continue

Storage Class Specifiers

auto
extern
register
static

Constants

const
volatile

Pointers and Memory Management

sizeof
typedef

Functions

return
void

Others

goto
struct
enum
union

Understanding C Keywords with Examples

1. `int`

Used to declare integer variables.

#include <stdio.h>
int main() {
    int num = 10;
    printf("Value: %d\n", num);
    return 0;
}

2. `if` and `else`

Control flow based on conditions.

#include <stdio.h>
int main() {
    int age = 18;
    if (age >= 18) {
        printf("Eligible to vote.\n");
    } else {
        printf("Not eligible to vote.\n");
    }
    return 0;
}

3. `for`

Used for looping.

#include <stdio.h>
int main() {
    for (int i = 0; i < 5; i++) {
        printf("Iteration: %d\n", i + 1);
    }
    return 0;
}

4. `typedef`

Defines new data types.

#include <stdio.h>
typedef unsigned int uint;
int main() {
    uint num = 100;
    printf("Value: %u\n", num);
    return 0;
}

5. `struct`

Groups variables into a single entity.

#include <stdio.h>
struct Student {
    char name[50];
    int age;
};
int main() {
    struct Student s1 = {"Alice", 20};
    printf("Name: %s\n", s1.name);
    printf("Age: %d\n", s1.age);
    return 0;
}

Best Practices for Using Keywords

Avoid Conflicts: Do not use keywords as variable or function names.
Consistency: Always use lowercase for keywords since C is case-sensitive.
Comment Usage: Include comments to clarify how and why specific keywords are used.

Common Errors with C Keywords

Misusing Keywords

Incorrect:

int float = 10; // Error: float is a keyword

Correct:

int value = 10;

Case Sensitivity