In programming, the **double integer data type** is a numerical data type that can store whole numbers. It is commonly used to represent integer values in computer programs. The double integer data type is also known as __int__ or __integer__.

## Declaration and Initialization

To declare a variable of the double integer data type, you can use the following syntax:

` ``int variableName;`

You can also initialize the variable at the time of declaration:

` ``int variableName = 42;`

## Range and Size

The range and size of the double integer data type depend on the programming language and the system architecture. In most programming languages, an int typically has a size of 32 bits, allowing it to represent values from -2,147,483,648 to 2,147,483,647.

### In C/C++:

In C/C++, you can use the limits.h header file to determine the range and size of int using predefined constants:

` ````
#include <limits.h>
printf("Size of int: %zu bytes\n", sizeof(int));
printf("Minimum value of int: %d\n", INT_MIN);
printf("Maximum value of int: %d\n", INT_MAX);
```

### In Java:

In Java, you can use the Integer class to retrieve information about the range and size of int:

` ````
System.out.println("Size of int: " + Integer.SIZE / 8 + " bytes");
System.println("Minimum value of int: " + Integer.MIN_VALUE);
System.println("Maximum value of int: " + Integer.MAX_VALUE);
```

## Operations and Usage

The double integer data type supports various mathematical operations, such as addition, subtraction, multiplication, and division. You can perform calculations using int variables just like any other numerical data type.

Double integers are commonly used for counting and indexing elements in arrays, looping constructs, and many other scenarios where whole numbers are required.

## Example:

Here’s an example that demonstrates the usage of the double integer data type:

` ````
#include <stdio.h>
int main() {
int count = 0;
for (int i = 1; i <= 10; i++) {
count += i;
}
printf("Sum of numbers from 1 to 10: %d\n", count);
return 0;
}
```

This program calculates the sum of numbers from 1 to 10 using a double integer variable. The result is then printed using the printf function.

## Conclusion

The double integer data type is a fundamental part of programming languages. It allows you to store and manipulate whole numbers efficiently. Understanding its declaration, range, size, operations, and usage is essential for any programmer.