FreeBasic ULong Keyword

Last modified October 18, 2026

The FreeBasic ULong keyword represents an unsigned 32-bit integer data type. It can store values from 0 to 4,294,967,295 (2^32 - 1). ULong is useful when working with large positive numbers.

Basic Definition

In FreeBasic, ULong is a built-in unsigned integer type that occupies 4 bytes (32 bits) of memory. Unlike signed types, it cannot represent negative numbers but has a larger positive range.

ULong variables are commonly used for counting, array indexing, and bit manipulation. They prevent overflow when dealing with large positive values. The type suffix for ULong is UL or ul.

Declaring ULong Variables

This example shows how to declare and initialize ULong variables.

ulong_declare.bas

Dim population As ULong
Dim fileSize As ULong = 4294967295UL
Dim counter As ULong = 1000000UL

Print "population: "; population
Print "fileSize: "; fileSize
Print "counter: "; counter

Here we declare three ULong variables. The first is uninitialized and defaults to 0. The others are explicitly set to values. Note the UL suffix used to indicate ULong literals. This helps prevent overflow during assignment.

ULong Arithmetic Operations

ULong variables support standard arithmetic operations with some limitations.

ulong_arithmetic.bas

Dim a As ULong = 4000000000UL
Dim b As ULong = 300000000UL

Print "Addition: "; a + b
Print "Subtraction: "; a - b
Print "Multiplication: "; a * 2UL
Print "Division: "; a / 2UL
Print "Modulus: "; a Mod b

This example demonstrates basic arithmetic with ULong values. All operations must stay within the 0 to 4,294,967,295 range. Attempting to go below zero wraps around to the maximum value due to unsigned nature.

ULong in Loops

ULong can be useful for loops with large iteration counts.

ulong_loop.bas

Dim i As ULong = 4294967290UL
Do
    Print "Count: "; i
    Sleep 200
    If i = 4294967295UL Then Exit Do
    i += 1
Loop

This loop counts up to the maximum ULong value. A plain For loop ending at 4294967295UL would never terminate, because incrementing past the maximum wraps the counter back to 0; so the loop exits explicitly when the maximum is reached. The Sleep pauses make the output readable as it counts up.

ULong with Bitwise Operations

ULong is well-suited for bit manipulation due to its fixed size.

ulong_bitwise.bas

Dim flags As ULong = &B11001100110011001100110011001100UL

Print "Original: "; Bin(flags, 32)
Print "AND: "; Bin(flags And &HFFFFFFFFUL, 32)
Print "OR: "; Bin(flags Or &H0000000FUL, 32)
Print "XOR: "; Bin(flags Xor &HAAAAAAAAUL, 32)
Print "NOT: "; Bin(Not flags, 32)
Print "Shift Left: "; Bin(flags Shl 4, 32)
Print "Shift Right: "; Bin(flags Shr 4, 32)

This shows bitwise operations on a ULong value. The Bin function displays results in binary format. ULong's fixed 32-bit size makes it predictable for bit manipulation unlike variable-size types.

ULong Array Example

Arrays of ULong can store large quantities of unsigned data efficiently.

ulong_array.bas

Dim primes(0 To 4) As ULong = {2UL, 4294967291UL, 4294967293UL, _
                               4294967295UL, 7UL}

For i As ULong = 0 To 4
    Print "Prime "; i; ": "; primes(i)
Next

This creates an array of ULong values including some very large primes near the maximum ULong value. The array indexing uses ULong for consistency, though smaller indexes would work with Integer too.

ULong Function Parameters

Functions can accept and return ULong values for large-number operations.

ulong_function.bas

Function Factorial(n As ULong) As ULong
    If n <= 1 Then Return 1UL
    Return n * Factorial(n - 1UL)
End Function

Dim num As ULong = 12UL
Print num; "! = "; Factorial(num)

This recursive factorial function uses ULong to handle larger results than signed types could. Note that factorial grows very quickly - even ULong will overflow at 13! (13 factorial exceeds ULong's maximum value).

ULong Type Conversion

FreeBasic handles conversions between ULong and other numeric types.

ulong_conversion.bas

Dim ul As ULong = 4000000000UL
Dim i As Integer = -1

Print "ULong to Long: "; CLng(ul)
Print "Integer to ULong: "; CULng(i)
Print "ULong to Single: "; CSng(ul)
Print "Single to ULong: "; CULng(12345.678)

This demonstrates explicit type conversion with ULong. Converting a large ULong to a 32-bit signed type such as Long may produce unexpected results: 4000000000 becomes -294967296. Integer is 8 bytes on 64-bit builds of FreeBasic, so CInt keeps the value 4000000000 there. Negative numbers convert to large positive values when going to ULong: -1 becomes 4294967295.

Best Practices

Use for large values: Prefer ULong when working with numbers > 2 billion.
Unsigned operations: Be aware that subtraction can wrap around.
Type suffixes: Use UL suffix for literals to prevent overflow.
Loop counters: Use for very large loops where Integer might overflow.
Bit operations: Ideal for bit manipulation due to fixed size.

This tutorial covered the FreeBasic ULong keyword with practical examples showing its usage in different scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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