QB64 is a modern extended BASIC programming language that retains QBasic/QuickBASIC 4.5 compatibility and compiles native binaries for Windows, Linux, and macOS.
THEN is required in IF…THEN conditional evaluation statements.
Syntax
IF condition THEN execute_code
THEN is required on the same code line as the IF statement.
The condition value must be true(-1) or <> 0 for the statement code to be executed.