Keywords in C

Keywords in C are predefined, reserved words used in programming that have special meanings to the compiler. These keywords help define the syntax and structure of the C programming language.
They cannot be used as variable names, function names, or any other identifiers. Keywords are the foundation of any C program, and understanding them is crucial for coding in C.

Below is a list of C keywords and their descriptions:

  1. Data Types
  2. Control Statements
  3. Storage Classes
  4. Operators
  5. Others

1) Data Types

C provides several built-in data types such as int, float, char, and double, which are used to define variables and return types of functions. These keywords define the type and size of data.

2) Control Statements

Control statements include keywords like if, else, switch, case, for, while, do. These are used to control the flow of execution in a program.

3) Storage Classes

Storage classes determine the scope, visibility, and lifetime of variables. Examples include auto, register, static, extern.

4) Operators

Keywords like sizeof, typeof are used for specific operations in C. These keywords help perform operations efficiently in the C environment.

5) Others

Other reserved keywords like return, goto, typedef, void have unique purposes within the C programming framework.

Reserved Keywords in C

The following table lists all the reserved keywords in C:

Keyword Description
int Defines integer data type
float Defines floating-point data type
return Returns a value from a function
if Starts a conditional statement
else Defines an alternative path in a conditional statement
while Starts a loop that runs while a condition is true
for Starts a loop with a counter
switch Starts a multi-case conditional statement
case Defines a single condition in a switch statement
default Defines a fallback in a switch statement
void Defines a function that does not return a value
static Defines a static variable or function
extern Declares an external variable or function

Example Programs Using C Keywords

1. Basic Arithmetic


#include <stdio.h>
int main() 
{
    int a = 15, b = 10, result; // 'int' is a keyword
    result = a - b;
    printf("Result of subtraction: %d\n", result);

    return 0;
}

Output

Result of subtraction: 5

2. Conditional Statement


#include <stdio.h>
int main() 
{
    int age = 20;

    if (age >= 18) // 'if' and 'else' are keywords
    {
        printf("You are an adult\n");
    } 
    else 
    {
        printf("You are a minor\n");
    }

    return 0;
}

Output

You are an adult

3. Switch Statement


#include <stdio.h>
int main() 
{
    int day = 3;

    switch (day) // 'switch' and 'case' are keywords
    {
        case 1:
            printf("Monday\n");
            break;
        case 2:
            printf("Tuesday\n");
            break;
        case 3:
            printf("Wednesday\n");
            break;
        default:
            printf("Invalid day\n");
    }

    return 0;
}

Output

Wednesday

4. Loop Example


#include <stdio.h>
int main() 
{
    for (int i = 1; i <= 5; i++) // 'for' is a keyword
    {
        printf("Number: %d\n", i);
    }

    return 0;
}

Output

Number: 1
Number: 2
Number: 3
Number: 4
Number: 5

5. Using Enumerations


#include <stdio.h>
enum week {Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday}; // 'enum' is a keyword
int main() 
{
    enum week today;
    today = Wednesday;

    printf("Day of the week: %d\n", today);

    return 0;
}

Output

Day of the week: 3