The Cursor's Y Position

If the display has not reached the end of a line, the cursor's y position does not change.

if the following are true:

  • value of cell 27 at time t = 1
  • cursor x at time t < 39

then cursor y at time (t + 1) = cursor y at time t

The cursor remains on the same line, so the y position does not change.

For example, suppose that the following is true:

  • value of cell 27 at time 11 = 1
  • cursor x at time 11 = 2
  • cursor y at time 11 = 0

The cursor's x value is 2. Thus, the cursor's x value is less than 39. Then we conclude that

cursor y at time (11 + 1) = cursor y at time 11

After some substitutions and simplification, this becomes:

cursor y at time 12 = 0

click here for the full proof.

Try running the simulator below to see the display cursor y value stay the same.

Time: 0
LW Computer IO Simulator

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