Lesson 14:
Decision Making

1. Use an conditional statements to control the flow of a program

2. Combine conditionals and repeat loops to continually check a condition

3. Program a robot to follow a line on the ground

1. Use an conditional statements to control the flow of a program

Check for mission success in ‘Elliptical Troubles’ or ‘Incoming!’.

2. Combine conditionals and repeat loops to continually check a condition

Check for mission success in ‘Elliptical Troubles’. ‘Life on the Edge’ may be used as an alternate assessment. You may also use reflection question 2 to check student understanding of this programming construct.

3. Program a robot to follow a line on the ground

Check for mission success in ‘Elliptical Troubles’.

• Slideshow: ​Decision Making

• If block support article

• Color sensor support article

• Repeat Forever block support article

1. What’s one way that ‘Wait Until’ blocks are similar to ‘If’ blocks and one way that they are different?

Students should note that both ‘Wait Until’ blocks and ‘If’ blocks change the behavior of the program based on whether or not something is true. ‘Wait until’ blocks delay the execution of the next instruction until the condition is true, while ‘If’ blocks check only once, then execute an instruction ONLY if the condition is true (and sometimes execute a different instruction ONLY if it is false).

2. Why does the ‘If’ statement need to go inside a repeat loop in order to follow a line on the ground?

The ‘If’ statement only checks a condition once, so if the robot is to continually follow a line on the ground, it will need to check the condition inside the repeat loop that will repeat forever. This will cause the program to repeatedly check the condition as the robot moves through its environment.

3. Why might it be better to program a robot to follow a line rather than tell it exactly how to go somewhere?

Students should understand that line following allows robots to be more flexible in the types of environments that they can work. It is easier to program a robot to follow a line, then paint lines on the floors of its environments, than it is to individually program it to follow instructions for each environment in which it may find itself. Line following is a classic robotics task for this reason.

Q1. What does the If block require?

A1. A condition and an action to do for when the condition is met.

Q2. What is the Else for?

A2. Else can be used to determine the action (or actions) to perform when the condition is NOT met.

Q3. How can we check the condition repeatedly?

A3. We can place the If block inside a loop, like the Repeat Forever loop.