Lesson 0.2: Commands Run in Order
A sequence is a group of commands arranged in the order they run. The runner starts at the top of a connected stack, finishes one command, and then moves to the next connected command.
Order matters when one action depends on an earlier action. If a program prints a score before it changes the score, the old value appears. If it changes the score first, the new value appears.
Read this sequence from top to bottom:
- Move forward by 2.
- Turn right.
- Move forward by 1.
- Print
done.
The final position depends on both move commands and the turn between them. Swapping the first move and turn produces a different route even though the program contains the same blocks.
Predict before running
Build three connected print blocks with the values first, second, and third. Before you run, write down the output you expect. Run the program and compare the actual order with your prediction.
Next, move third above second. Run again. Stepping through the program should show the same order as the output panel.
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