LOGO conversations

Modes of interaction

There are two quite different modes of interaction with a LOGO system: a direct conversational mode and an indirect editing or definition mode. Which mode the programmer chooses will depend - as we shall see - on the situation. Editing mode has much in common with letter writing or sending a fax. Conversational mode is like . . . well, like face to face conversation.

Since there is - fortunately - no real difference in the form of the language used in the two different circumstances, we will begin with the most direct form of contact and take our initial look at LOGO within conversational mode. You will normally be taken automatically into this mode when you first start up LOGO so that you are ready to interact with the system via the keyboard. In this situation you are said to be at toplevel.

Conversational mode

Perhaps the easiest way to get some feel for the style of conversation possible in LOGO is to examine a sample transcript. In the following (very basic) interaction, each contribution is on a separate line, with the human input in lower case bold and the LOGO interpreter's response - if any - in upper case:

WELCOME TO LOGO!
print "cat
CAT
print last "cat
T
first "cat
YOU DON'T SAY WHAT TO DO WITH C
smile
I DON'T KNOW HOW TO SMILE
make "household [mum dad son daughter pet]
make "vehicle "car
print thing "vehicle
CAR
print thing "household
MUM DAD SON DAUGHTER PET
word thing "vehicle last thing "household
YOU DON'T SAY WHAT TO DO WITH CARPET
print word thing "vehicle last thing "household
CARPET

If you have Logo running right now, switch to it and try replicating this conversation by typing in the 'human input' lines in the Logo window (hitting the return key at the end of the line). Your version of Logo may not give exactly the same responses but two things will certainly strike you about the conversation. In the first place, it is easy enough, by and large, to get some grip on what it might mean. And in the second place, even taking a charitable view, it is looks pretty boring stuff.

The naturalness of LOGO was, of course, a primary goal of its developers. Their aim was to create a language readily accessible to young children. For that reason it had to be as transparent as possible in its expression, right down to the form of the error messages. And older users can be grateful for that. You don't hear SYNTAX ERROR 34 from LOGO!

As to the lack of sparkle, there is no denying that you would need to be desperate to switch on LOGO just for a gossip - unless, that is, you had previously taught it how to gossip. (And we will look later at an Eliza system which does aim to converse. ) The fact is that computers at heart are submissive creatures who like best of all being told what to do and LOGO, as you know, is an imperative language.

The nature of Logo conversations

Given such a relationship between man and machine,it should come as no surprise that the pattern of a LOGO conversation hinges on the human giving instructions and the computer obediently reacting. As a result, the verbal interplay is very often one sided. When the user has requested it, LOGO's reaction to an instruction may indeed be an overt response - in the manner of a genuine dialogue. But, unless required to reply, LOGO is quite content to do quietly what it is told. Only if an instruction is not understandable will LOGO respond automatically - in this case with an error message. As reproduced on the screen, then, a LOGO conversation reads as a series of user instructions interspersed with LOGO responses (where requested), LOGO silences and LOGO complaints. The single concession to social convention is the greeting which most LOGOs provide on startup of the system.

Error messages

If you were to examine the components of conversations in more detail, you would soon discover that LOGO error messages are standard stereotyped sentences with easily remembered forms. The more mistakes you make, the sooner they become familiar. We need therefore say no more about them here. (See errors for a list of common messages.)

Instructions

Since, aside from error messages, all other responses from LOGO are ultimately determined by the user's own instructions to the system, an understanding of the key elements of a conversation is best reached by focussing attention on the components and on the form of instructions. (Click this link or click the Next page button below.)

Ron Brasington
Department of Linguistic Science
The University of Reading
Reading
UK

E-mail: ron.brasington@rdg.ac.uk