C unsigned long Data Type

C `unsigned long` Data Type

In C, the unsigned long data type is used to store large positive whole numbers. Unlike long, which can store both positive and negative values, unsigned long can only store non-negative values, but it has a greater positive range.

1 Storage Size of `unsigned long` Data Type

The storage size of unsigned long depends on the system architecture and compiler. Typically, the sizes are:

System / Model	`unsigned long` Size
32-bit system (ILP32)	4 bytes (32 bits)
64-bit Windows (LLP64)	4 bytes (32 bits)
64-bit Linux/macOS (LP64)	8 bytes (64 bits)

2 Values Stored by `unsigned long` Data Type

The unsigned long data type can store only positive whole numbers, including zero. It does not support negative values.

Example values that can be stored in unsigned long:

0, 1000, 4294967295 (on a 32-bit system), 18446744073709551615 (on a 64-bit system)

3 Example: Declaring and Using `unsigned long` Variables

Let’s see a simple program demonstrating how to declare and use unsigned long variables in C.

main.c

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#include <stdio.h>

int main() {
    unsigned long num1 = 100000;
    unsigned long num2 = 500000;
    unsigned long sum = num1 + num2;

    printf("Number 1: %lu\n", num1);
    printf("Number 2: %lu\n", num2);
    printf("Sum: %lu\n", sum);

    return 0;
}

Explanation:

We declare three unsigned long variables: num1, num2, and sum.
We assign values 100,000 and 500,000 to num1 and num2 respectively.
The sum of these numbers is stored in sum.
We use printf() with the %lu format specifier to print the values.

Output:

Number 1: 100000
Number 2: 500000
Sum: 600000

4 Checking Storage Size of `unsigned long` Programmatically

We can determine the storage size of unsigned long using the sizeof operator.

main.c

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#include <stdio.h>

int main() {
    printf("Size of unsigned long: %lu bytes\n", sizeof(unsigned long));
    return 0;
}

Output (varies based on system architecture):

Size of unsigned long: 8 bytes

5 Minimum and Maximum Values of `unsigned long`

The range of values an unsigned long can store depends on its size:

Storage Size	Minimum Value	Maximum Value
4 bytes	0	4,294,967,295
8 bytes	0	18,446,744,073,709,551,615

6 Getting Maximum Value of `unsigned long` Programmatically

The maximum value of an unsigned long can be retrieved using limits.h.

main.c

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#include <stdio.h>
#include <limits.h>

int main() {
    printf("Maximum unsigned long value: %lu\n", ULONG_MAX);
    return 0;
}

Output:

Maximum unsigned long value: 18446744073709551615

Conclusion

In this tutorial, we explored the unsigned long data type in C, including:

Its ability to store large positive whole numbers.
Its typical storage size of 4 or 8 bytes, depending on the system.
How to get the storage size programmatically using sizeof().
The maximum value that unsigned long can store.
How to retrieve the maximum value using limits.h.

The unsigned long data type is useful when dealing with large numbers that do not require negative values.

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