Check If a Key is Pressed in Basic4GL

How to Check if a Key is Pressed in Basic4GL

Checking whether or not a key is pressed down is the first step of programming more complicated player control using the keyboard. How you check a key will depend on whether it is a "typeable key" or if it is a special key, such as the "arrow" keys.

Checking "Typeable" Key

A typeable key is a key that you type to get a letter, number or character. For these keys, you can use KeyDown().

If KeyDown("A") Then Printr " ' A ' key down. " EndIF

Checking Special Keys

Checking special keys requires ScanKeyDown() and a virtual keycode. A virtual keycode is a built-in constant that refers to that key. They begin with vk_.

If ScanKeyDown(vk_left) Then Printr " ' Left ' key down." EndIF

Complete Source Code

TextMode(TEXT_BUFFERED)

Do 
    Cls
    If KeyDown("A") Then Printr " ' A ' key down. " EndIF
    If ScanKeyDown(vk_left) Then Printr " ' Left ' key down." EndIF

    Printr "(press escape to exit)"
    DrawText()
Loop

End

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