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The Microprocessor: Peanut Butter
& Jelly 
Goal
Students will understand that the microprocessor follows a precise set of instructions.
Activity
For higher grade levels, use a more complicated task such as putting on a coat, tying your
shoe.
Grade level
Grades 4-8
Key Concepts
- The microprocessor is the Central
Processing Unit for the computer. It controls what the computer does.
- Microprocessors follow a precise set of
instructions called a program.
- Microprocessors do very complex tasks by
breaking them down into simple steps.
- Microprocessors are often called the
brain of the computer, but they are very different from a human brain.
Many people refer to the microprocessor
as the "brain" of the computer. You may sometimes hear it called a Central
Processing Unit or CPU. Like your brain, it is the central place where information is
processed and it tells the other parts of the computer what to do by taking input and
directing output. It is very different from a human brain because it does not think for
itself, it only does what it is told to do.
Every job a microprocessor does is
broken down into a set of separate little operations with a coded instruction for each
task. This list of instructions is called a program. We can program microprocessors to
perform certain tasks for different situations. Unlike our brains, microprocessors do not
think. Therefore the instructions, or program, given to a microprocessor must be very
precise.
Lesson
Materials
A sample microprocessor or
picture of one to show the class Chalk and chalkboard or white board with pens or flip
chart and pens Peanut butter, jelly and several slices of bread, dull or plastic knife and
a spoon
Directions
Note:
This is intended to be a fun activity with lots of student interaction. Do not feel shy
about "hamming" up the directions.
- Tell the class that they are going to
write instructions to program a microprocessor that controls a robot. The program will be
a set of instructions for making a peanut butter and jelly sandwich. On the front table
there are pieces of bread, an open jar of peanut butter and an open jar of jelly. There is
also a knife and a spoon.
- You will be the robot.
- Ask the students to think about how to
make a PBJ sandwich and how they would write the program. Students then write the program.
40 minute version--Students work in small groups to prepare their program. Each group
submits one set of instructions. 25 minute ver- sion--Ask the students for the first
instruction, second and so on. Write the instructions on the board. After the first four
or five instructions tell the class you will now try the first few.
- Follow the instructions exactly. The
instructions will be unclear and steps will be missing (like using a knife, or the bread).
If the instruction says 'put the peanut butter on the bread' you might put the jar of
peanut butter on the bread. Ask the students what is wrong? They will quickly see that the
instructions were not specific enough or possibly whole steps were omitted.
- Once the class understands that more
precise instructions are needed, have the students "de-bug" the program again
and then summa- rize the lesson by reviewing the following: Microprocessors can perform
complex tasks when given a precise set of instructions that break that task down into
simple steps. The microprocessors can be programmed to handle different situations but,
unlike a human brain, the microprocessor cannot make decisions. Therefore the
instructions, or program must be very exact.
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