FreeBasic Loop While Keyword

last modified June 16, 2025

The FreeBasic Loop While construct creates a loop that executes a block of code repeatedly while a condition remains true. It checks the condition after each iteration, ensuring the loop runs at least once.

Basic Definition

In FreeBasic, Loop While is a post-test loop structure. The loop body executes first, then the condition is evaluated. If true, the loop repeats.

This differs from While Wend which checks the condition before execution. Loop While is useful when you need to guarantee at least one iteration occurs.

Simple Loop While Example

This basic example demonstrates the fundamental structure of a Loop While.

loop_while_simple.bas

Dim counter As Integer = 1

Do
    Print "Iteration: "; counter
    counter += 1
Loop While counter <= 5

The loop prints numbers from 1 to 5. The condition checks after each iteration. Even if counter started at 6, the loop would run once before checking the condition.

User Input Validation

Loop While is ideal for input validation where you need at least one prompt.

loop_while_input.bas

Dim age As Integer

Do
    Input "Enter your age (1-120): ", age
Loop While age < 1 Or age > 120

Print "Valid age entered: "; age

This code repeatedly prompts for age until a valid value is entered. The loop always runs at least once, ensuring the user sees the prompt before any condition check.

Password Verification

Loop While works well for password verification scenarios.

loop_while_password.bas

Dim password As String
Dim attempts As Integer = 0
Const CORRECT_PASSWORD = "secret123"

Do
    Input "Enter password: ", password
    attempts += 1
Loop While password <> CORRECT_PASSWORD And attempts < 3

If password = CORRECT_PASSWORD Then
    Print "Access granted!"
Else
    Print "Too many attempts!"
End If

This example limits password attempts to three. The loop continues until either the correct password is entered or attempts are exhausted. The condition combines two checks with a logical AND.

Menu System

Loop While can control a simple text-based menu system.

loop_while_menu.bas

Dim choice As String

Do
    Print "1. Play game"
    Print "2. View scores"
    Print "3. Exit"
    Input "Enter choice: ", choice
    
    Select Case choice
        Case "1"
            Print "Starting game..."
        Case "2"
            Print "Displaying scores..."
        Case "3"
            Print "Goodbye!"
        Case Else
            Print "Invalid choice"
    End Select
Loop While choice <> "3"

The menu displays until the user selects option 3 to exit. The loop structure ensures the menu always shows at least once. The Select Case handles different menu options.

Random Number Generation

Loop While can generate values until a condition is met.

loop_while_random.bas

Randomize Timer
Dim number As Integer

Do
    number = Int(Rnd * 100) + 1
    Print "Generated: "; number
Loop While number < 90

Print "Found number >= 90: "; number

This generates random numbers between 1-100 until one >= 90 is found. The loop runs at least once, and the condition is checked after each random number generation.

File Reading

Loop While can process file contents until the end is reached.

loop_while_file.bas

Dim fileNum As Integer = FreeFile()
Dim line As String

Open "data.txt" For Input As #fileNum

Do
    Line Input #fileNum, line
    Print "Line: "; line
Loop While Not EOF(fileNum)

Close #fileNum

This reads a file line by line until EOF (End Of File) is reached. The loop structure ensures each line is processed, with the condition checked after each read operation.

Nested Loop While

Loop While statements can be nested to handle complex scenarios.

loop_while_nested.bas

Dim outer As Integer = 1
Dim inner As Integer

Do
    inner = 1
    Print "Outer loop: "; outer
    
    Do
        Print "  Inner loop: "; inner
        inner += 1
    Loop While inner <= 3
    
    outer += 1
Loop While outer <= 2

This demonstrates nested Loop While structures. The outer loop runs twice, and for each iteration, the inner loop runs three times. Indentation helps visualize the nesting level.

Best Practices

Initialization: Ensure variables are initialized before the loop.
Termination: Guarantee the condition will eventually become false.
Readability: Use clear conditions and proper indentation.
Comments: Add comments for complex loop conditions.
Performance: Avoid expensive operations in the condition check.

This tutorial covered the FreeBasic Loop While 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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