Learning With Computers
Glenn M Kleiman
Are you interested in learning the Logo language? Or have you already begun using Logo or teaching it to others? If so, have you or your students encountered any confusion that was frustrating and delayed progress? Would you like more guidance in understanding and explaining what you have heard called the "powerful ideas" inherent in Logo? Do you want to go beyond simple turtle graphics commands and explore more complex procedures, recursion, and language processing? Would you like suggestions from a Logo expert who is also an experienced teacher of the language? If you have answered yes to any of these questions, then I recommend that you get a copy of Learning with Logo by Daniel Watt (McGraw-Hill, 1983, $19.95).
I have used the version of this book designed for MIT (that is, Terrapin or Krell) Logo for the Apple Computer. It contains an appendix explaining differences between MIT Logo, Apple Logo, and TI Logo. Another version of the book is available specifically for users of Apple Logo. Versions for Atari Logo and Commodore 64 Logo are forthcoming.
Learning with Logo is designed to be used with a preprogrammed disk. The disk contains "tool" procedures that can be used as if they were built-in Logo commands. These procedures support many of the lessons in the book. The disk also contains longer programming examples so you can explore them without first typing them. You can order a copy of the disk for Apple, MIT, or TI Logo. The cost is $15.95, and the author gives permission to make a copy of the disk for anyone else who has purchased the book. All the procedures on the disk are given in an appendix of the book, so you can also type and save them on a disk yourself.
A Wealth Of Information
Learning with Logo is 365 pages long, divided into an introduction, 14 chapters, 4 appendices, and an index. Each chapter begins with a list of the commands and procedures introduced in that chapter, and then gives explanations and examples of how they can be used. The book is well illustrated with clever cartoons and pictures of what you should see on the computer screen as you work through the examples.
Chapter 1 gets you started with Logo. It explains how to load Logo into the computer, use the keyboard, and enter commands. It also introduces the turtle and the FORWARD, BACKWARD, LEFT, and RIGHT commands. Chapter 2 covers the remaining turtle graphics commands.
Chapter 3 contains two special turtle activities called Shoot and Quickdraw. They are ready to load and use. How they are programmed is discussed later in more advanced chapters.
Shoot is a simple game. The computer draws a target in a randomly selected position on the screen and places the turtle elsewhere. The player uses LEFT and RIGHT commands to turn the turtle directly toward the target and then specifies how far forward the turtle should move to reach the target. This game is designed to help children learn to estimate angles and distances.
Quickdraw is a simple drawing tool. There are six simple commands: F moves the turtle forward 20 steps; B moves it backward 20 steps; R turns the turtle 30 degrees to the right; L turns it 30 degrees to the left; E ends the drawing and lets you give the picture a name; and RD followed by a name of one of your pictures tells the computer to redraw it. Quickdraw is usable by young children and introduces some of the major concepts of Logo, including building complex shapes out of simple building blocks.
Chapter 4 explains how you can teach the computer new Logo procedures. It also explains how to use the Logo screen editor and how to save procedures on a disk.
Chapters 5 and 6 further elaborate the use of turtle graphics commands and procedures. It presents sample projects in which Logo procedures are used to create designs and pictures.
Chapter 7 introduces the important concept of variables. It also covers some of the ways procedures can be programmed to interact and exchange information. This includes an explanation of recursive procedures.
Chapter 8 further explores the concepts introduced in Chapter 7. It explains a procedure called POLY, which is used to draw polygons. POLY has two variables: SIZE (of a side) and ANGLE (number of degrees). Many different patterns and designs can be created by changing these variables and recursively repeating the POLY procedure.
Chapter 9 introduces the fundamental commands for working with numbers, words, and lists. These complete the basics needed to begin working with the four larger projects described in Chapters 10 through 13,
Chapters 10 and 11 explain in detail the programs for the Shoot and Quickdraw activities introduced in Chapter 3. The project in Chapter 12 is a race-track game which shows how simple animations can be created. The final project, described in Chapter 13, uses the list-processing commands for working with language. The program has the computer randomly select words from different sets and combine them into sentences and "poems."
The final chapter explains how the special tool procedures on the disk operate. These include procedures for drawing circles and arcs, determining the distance between the turtle and a specified point, counting the number of letters in a word or words in a list, and several others.
The appendices explain how to create your own disk of the procedures used in the book; discuss the differences among MIT, Apple, and TI Logo; explain the use of disks and files; and present a summary of Logo commands.
As this description of the chapters suggests, the book contains a wealth of information about Logo. The early chapters are suitable for complete beginners while the later ones explain sophisticated programming techniques. The book goes well beyond turtle graphics to explain how Logo can be used with numbers, words, and lists. The examples and discussions are all clearly and carefully presented. The material is well-sequenced, with the lessons and programs in each chapter building on what was learned in prior chapters. The many illustrations aid both understanding and interest. And I have not yet described what I regard as the best features of this book.
Helpful Cartoon Symbols
Special cartoon symbols mark what the author calls pitfalls, explorations, powerful ideas, and helper's hints. Each symbol marks information that goes beyond the description and explanation of Logo to provide additional guidance and insight.
Pitfalls are confusions or difficulties that many people encounter while learning Logo. The pitfall symbol (a turtle which has fallen into a trap) marks explanations that will help you avoid or get out of pitfalls. Some pitfalls are simple reminders for beginners, like putting a space between a FORWARD command and the number of steps the turtle is to move. Others, such as pitfalls in using recursive procedures, are for more advanced users of Logo.
Powerful ideas help you think more clearly and solve problems with the computer more easily. Some of these ideas, such as dividing a complex problem into a series of simpler ones, will also help you solve problems that do not involve the computer at all. A cartoon symbol of a turtle with a bright idea designates explanations of powerful ideas. These explanations are important for helping learners see the general principles while they work with specific examples.
Explorations are necessary to become proficient with Logo, but most learners need suggestions for things to explore. These are provided throughout the book, marked by a picture of a turtle with a map and spyglass. Many of the explorations are suggestions for modifying and extending programs given in the book.
Helper's hints explain difficult points and pitfalls more fully, suggest learning activities, and give other practical suggestions for teaching. These are marked by a symbol showing two turtles — an older and a younger one — helping each other learn by shining a bright light on the subject. Helper's hints can help you learn more about Logo and help you teach others.
Daniel Watt, the author of Learning with Logo, is a former researcher with the MIT Logo group and an experienced Logo teacher. The clarity, organization, and special aids in this book reflect both his expertise with the language and his abilities as a teacher. Learning with Logo comes closer to bringing a master teacher to your side than any other book I have seen.