! Write a subroutine to clear the entire screen and

! fill it with an 80 by 24 grid of dots.

! Such a subroutine might be used in a

! computer graphics program.

! Test the program with i >= 3, j >= 5 first, do trace, slow (i,j)

! Set i >= 24, j >= 80

! Test the program with do trace, fast(i,j)

DO until i >= 24

LET j= 0

DO until j >= 80 !write a row of periods

LET j=j+1

PRINT ".";

LOOP

PRINT !go to the next line

LET i = i + 1

IF mod(i,2) > 0 then

SET COLOR "red"

ELSE

SET COLOR "blue"

END IF

LOOP

SOUND 1000 ,.1

END

The output:

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