SUB sayHello
    DIM I as INTEGER      ' this variable is local to the sayHello SUB procedure
    
    FOR I=1 to 3
        PRINT "Hello"
    NEXT I
    
ENDSUB
...

MAIN:
...
I = 55
PRINT I                        ' will display 55
 
GOSUB sayHello

PRINT I                        ' will still display 55, as this is the global I, different from sayHello local I
....