This document introduces Jeroo, a graphical programming environment similar to Visual Basic used to teach object-oriented programming concepts. Jeroos are programmable agents that live on Santong Island and can be given instructions to perform tasks. Fundamental Jeroo behaviors include hopping, turning, manipulating flowers by picking, planting, tossing or giving them to other Jeroos. Example tasks for Jeroos include navigating the island, completing races, escaping areas and finding or harvesting flowers. The document outlines the basic hop and turn instructions used to write programs that send messages to Jeroos, providing a sample program to hop and turn as an example. Good programming style with indentation, comments and organization is encouraged.

1. Jeroo
A Gentle
Introduction to the
Art of Object
Oriented
Programming

2. Jeroo
Santong
Island

3. Modeling a Jeroo
 Jeroo
– A graphical interface, similar to VB, used to
illustrate concepts we will study in this
course.
– We will learn how to write instructions
(programs) so that our programmable jeroos
can perform the tasks we give them.
 Unfortunately no variables

4. A Jeroo on its Island

5. Fundamental Jeroo Behaviors
 Jeroos are mobile.
– Can hop forward in the direction it is facing, from
corner to corner.
– Can turn in place.
 Jeroos can manipulate flowers.
– Can Pick flowers that they are on top of.
– Can plant a flower at their current location.
– Can toss a flower one space ahead.
– Can give a flower to a neighboring Jeroo
– Can determine if they are carrying any flower
 Jeroos can navigate by detecting the direction it is facing
(north, south, east, west).

6. Tasks
 A task is something that we want a jeroo
to do. Some examples are:
– Move to the corner of the island
– Run a hurdle race (jump over nets or water)
– Escape from a sectioned off fragment of
island
– Find a flower and place it at the origin.
– Escape from a maze.
– Harvest rows of flowers.

7. Jeroo
Primitive
Instructions and
Simple Programs

8. How Do We Tell the jeroo
What to Do?
 We give the jeroo instructions.
 A jeroo executes an instruction by
performing the instruction’s associated
action or actions.
 The jeroo executes a program by
executing a sequence of instructions that
are given to it by “the island god”.

9. Fundamental Jeroo Functions
 Changing position
hop()
– Hop one space ahead.
– The program terminates with a logic error if the
hopping Jeroo lands in the water, lands on another
Jeroo, or hops onto a net.
– A Jeroo can hop onto a flower.
turn(dir)
 Pivots 90 degrees in the specified direction.
– LEFT or RIGHT

10. Sending a message
 To send a message, we must specify the object
and the behavior for that object.
– A reference to the receiver object
– A period
– The message to be sent
 To send a message to a Jeroo:
silver.hop()
reference message

11. The Instructions
Silver = Jeroo(0, 0, East, 0)
silver.hop()
silver.hop()
silver.hop()
silver.turn(LEFT)
silver.hop()
silver.hop()
silver.hop()
// trace to see that it works
Sending a Message or invoking a function

12. Style Issues
 Programs should be indented nicely.
 Comments should be included.
 Programs should be well organized.
 Programs should be easy to read.