Returns the number of characters waiting in the input buffer.
In UTF-8 supporting versions 4.5.1 and higher NULL characters are no longer cut
out from strings, resulting in a different behavior:
Len of Chr$(0) is 1:
In former versions NULL characters could not appear in the middle of strings, since the concationation process cut these characters from the resulting string.
<DeviceHandle>: A handle to a specified port.
<return value>: Long
<DeviceHandle>: 1 to 255
<return value>: 0 to512
Configuration, Task or Terminal