The program:

! this program shows how the logical variables end data and

! more data change, depending on whether there is or is not

! more data available for reading

SET COLOR "blue"

IF end data then PRINT "end data is true" else PRINT "end data is false"

! gives true without data statement, false with

IF more data then PRINT "more data is true" else PRINT "more data is false"

! gives false without data statement, true with

DATA 2,3,4,5,6,7,8,9

DO while more data

READ num

LOOP

SET COLOR "red"

IF end data then PRINT "end data is true" else PRINT "end data is false"

! gives true without data statement, false with

IF more data then PRINT "more data is true" else PRINT "more data is false"

! gives false without data statement, true with

END

The output of the program:

before reading the data

end data is false

more data is true

after reading the data in a do-loop controlled by while more data

end data is true

more data is false