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Introduction to the LOGO Language

by R. Barrett, B. DeRoos and L. Taylor


Bar_gold.gif 401 bytes THREE (3) SPECIAL WORK AREAS IN LOGO:

1. The TURTLE SCREEN or Play Pen (Graphics Area) where the turtle draws with a pen taped to his middle.

 

 

 

 

 

 

 

 

 

 

2. The COMMAND CENTER under the Play Pen. Use [Ctrl]U to go to the Play Pen and or [Ctrl]D to return to Command Center. You issue commands in the Command Center like FD 50 togo forward 50 steps.

 

 

 

 

 

 

 

 

 

 

 

3. The PROCEDURE SCREEN of "Flip Side" i.e. the Turtle's memory. To go to Flip Side press [Ctrl] F and use the same keys to return to the play pen page. You put or write procedures here like TO BOX below. Then you can use the procedure in the Command Center by typing BOX. When you turn off the computer or get out of LOGO, you lose all the commands in the Command Center. Only procedures and the pictures in the Play Pen are saved when the page is saved. So I call the procedure page the Turtle's Mind because you can teach turtle things to do here and he will remember.























SPECIAL KEYS:

[Ctrl][Pause] STOP a turtle trip or a calculation.
[Ctrl]F FLIP to the FLIP or PROCEDURE screen.
[Ctrl]U To put cursor into the Play Pen for labeling or adding text
[Ctrl]D To go DOWN to COMMAND TABLET from Play Pen
[Ins] To get a fresh line on the Command Center


SYSTEM COMMANDS:

PRINTSCREEN Prints what is visible on the turtle Play Pen
PRINTTEXT Prints TEXT only. To print out PROCEDURES, flip to the procedure Page, use [Ctrl]D to get to the Command Center. Type PRINTTEXT.


COMMANDS:

RG Reset or Clear Graphics
CC Clear Command Center
CG Clear Graphics
CT Clears TEXT in the TURTLE TABLET
RT __ Right Turn (Degrees)
LT __ Left Turn (Degrees)
FD __ Forward (Turtle Steps)
BK __ Back Up (Turtle Steps)
REPEAT __ [ commands ] (Number of Repeats) Command to Repeat Commands
PE Pen Erase removes a line that turtle covers.
PU Pen Up turtle does not make a line
PD Pen Down turtle draws and the STAMP command works
HT Hide Turtle
ST Show Turtle (opposite of Hide Turtle)
PRINT [_______] Puts TEXT on the Play Pen with CARRIAGE RETURN
RANDOM nn Selects an Unexpected NUMBER from 0 TO nn
SETBG __ Choose a Color 1 to 8:
SETC nn Set or Change Turtle's COLOR and color of lines; use a number 1 to 15
SETSH nn Set SHAPE. Choose from 35 or more shapes see TABLE below.
STAMP Prints SHAPE of TURTLE on SCREEN & LEAVES it there!


MATH COMMANDS:

A variable when defined has a (Quotation Mark) in Front "X but when used it has (Colon) in Front :X Variables DO NOT have default VALUES. They must be defined before use!
MAKE "C 10 Assigns or defines C as 10.
MAKE "X :X + 1 Is Counting
IF___ [____] IF comparison [ commands ] e.g. IF :X > 10 [STOP]


PROCEDURES:

Must be typed on the FLIP page using F,
they must start with an infinitive like TO BOX (no spaces in procedure name), and they must end with an END on a separate line. Examples below:

TO STAR Draw a STAR
REPEAT 12 [FD 100 RT 160]
END

TO CIRCLE Draw a CIRCLE
REPEAT 36 [FD 5 RT 10] The RT angle and the number of repeats must be 360 for a full circle
END

TO BOX Draw a BOX
REPEAT 4 [FD 50 RT 90]
END

Bar_gold.gif 401 bytes

Bar_gold.gif 401 bytes