JEM Tutor First make a backup of the JEM disk. If you are unsure how to make a copy read the section in your DOS manual under the copy command.JEM must have a CGA or a EGA to work a color monitor is not necessary a mono (one color) monitor is ok with a CGA EGA. -------------------------------------- To use this tutorial print this file out to the printer or go back to DOS and type in "copy tutor.prn prn" hit enter.You will need a copy of this in front of you to use this tutorial. This tutorial assumes that you know some DOS commands , if you do not you will need your DOS manual. This tutorial will teach you how to use JEM step by step.So start on the first page and go through it slowly if you have a problem go back a page.After you get the hang of the commands JEM is very is easy to program in. First JEM is a LOGO like computer language or a Graphics language. You can write computer programs in the JEM language that will create geometric shapes by ordering the Turtle around the screen. The following tutorial will teach the basic commands of JEM. The commands must be enter exactly as in this tutorial if the screen does not look like the tutorial says it should reenter the commands. IMPORTANT TYPE IN THE COMMANDS EXACTLY IF A LETTER IS IN IMPORTANT TYPE IN THE COMMANDS EXACTLY IF A LETTER IS IN CAPITALS OR IF IT IS SMALLCAPS LOOK CLOSE AT THE COMMAND. CAPITALS OR IF IT IS SMALLCAPS LOOK CLOSE AT THE COMMAND. --------------------------------------------------- Put the JEM disk in Drive A , type "jem" the screen should blank and a small pyramid shape should appear in the center of the screen. The small pyramid shape is called the Turtle. The display should also be switched To the 40 character per line mode. The bottom line of the screen will look like the line below. ?- ! This is the command line all JEM commands are entered here. Type in help the screen will now be in 80 character per line help mode. The screen will have two columns the column on the left is the list of the commands "built into JEM" . The column to the right is a brief description of the command on the left,the last line reads "Press any Key for more Help". Press the space bar five (5)times. You have the Turtle in the center of the screen and the bottom line should look like the line below if the not press the space bar until the line appears. ?- ! This line is called the command line. Page 1 Moving the Turtle forward and back. To start to order the turtle around the screen type in forw [10] forw [10] then hit enter the turtle will move ahead ten (10) spaces. And will leave a line behind it. Type in back [20] then hit enter the back [20] turtle will back up twenty (20) spaces. Try moving the turtle forward 15 spaces type in forw [15] hit enter forw [15] The turtle should move ahead fifteen spaces. Try moving the turtle back 12 spaces type in back [12] then hit enter. back [12] Try moving the turtle yourself when you feel confident in moving the turtle go on to next section. Clearing the Screen To clear the screen type in cs hit enter. The screen should be cs clear now. Turning the Turtle To turn the turtle type in turn [180] hit enter the turtle should turn [180] be facing the command line. Type in turn [360] hit enter the turn [360] turtle should be facing the top of the screen. The turtle may turned in any direction between 0 and 360 using this command. 0 270 T 90 180 Think of the top of the screen being 0 degrees and the bottom of the screen being 180 degrees. Or think of a compass ,the turn [angle] command will turn the turtle around like the pointer turn [angle] of a compass. Page 2 Hiding and Showing the Turtle The Turtle may be hidden (made to disappear) type in hide hit hide enter. The turtle should be gone type in show hit enter the turtle show should be back. Try this commands a few times. Drawing Lines and Centering the Turtle You can turn the line drawing by turtle on or off. Type in the command upen hit enter. Now type in the command back [25] hit upen back [25] enter. The turtle will have backed up 25 spaces and there will be no line drawn. Type in dpen hit enter , type in forw [25] hit dpen forw [25] enter. The turtle will have moved forward 25 spaces and drawn a line. Type in upen forw [30] hit enter the turtle should be 30 upen forw [30] spaces forward and there should be no line drawn. To put the turtle back in the center of the screen type gh hit gh enter. The turtle should be in the center of the screen. Switching Line Colors You can switch the color of the lines first clear the screen by using the clear screen command. Type in cs hit enter. cs Type in forw [5] Clr [3] forw [5] hit enter. You should have forw [5] Clr [3] forw [5] one line in two different colors. Type in Clr [2] forw [5] hit Clr [2] forw [5] enter. The number of pen colors are 4 per palette (between 0 and 3). Try using the Clr command. Switching Palettes To switch palettes type in 1 hit enter you now have the first 1 palette of colors. Type in 2 hit enter you now have the second 2 palette of colors. Turning Command line on or off You can turn the command line on or off to turn the line off type in Off hit enter. To turn the command line on type in Line hit Off Line enter. Switching to 80 or 40 Characters per line mode You can switch from 40 characters per line mode to the 80 character per line mode. Type in Hi hit enter you are now in the Hi 80 character per line mode. Type in med hit enter you are now in med the 40 character per line mode. Page 3 Exiting JEM Type in end hit enter the screen will clear and the dos prompt end will appear. To go on with this Tutorial - At the DOS prompt Type in jem hit enter jem You will now be back in the the JEM program. If the user has created a command JEM will ask if you wish to save the file before returning to DOS. (Note see loading and saving files). The next commands are more complex make sure you understand The next commands are more complex make sure you understand everything up to this point. everything up to this point. Drawing a Box Using the commands shown so far you may now order the Turtle to do some complex commands. Like drawing a box first clear the screen use the cs command. cs Type in cs hit enter. cs Type in forw [20] turn [90] forw [20] hit enter. forw [20] turn [90] forw [20] Type in turn [180] forw [20] hit enter. turn [180] forw [20] Type in turn [270] forw [20] hit enter. turn [270] forw [20] Now to hide the Turtle Type in hide hit enter. hide You will now have a box drawn on the screen. Now clear the screen and show the Turtle Type in cs show hit enter cs show Right and Left Turns You can turn the turtle right of its current position by using the right turn command. Type in rtrn [10] hit enter rtrn [10] (The turtle should be ten degrees right of where it started) (The turtle should be ten degrees right of where it started) Type in ltrn [10] hit enter ltrn [10] (The turtle should be 1ten degrees left of where it started) (The turtle should be 1ten degrees left of where it started) The rtrn [angle] and the ltrn [angle] will turn the turtle from rtrn [angle] ltrn [angle] the current position. To draw a box using the rtrn command rtrn First Clear the screen Type in cs hit enter cs Type in forw [20] rtrn [90] hit enter. forw [20] rtrn [90] Type in forw [20] rtrn [90] hit enter. forw [20] rtrn [90] Type in forw [20] rtrn [90] hit enter. forw [20] rtrn [90] Type in forw [20] rtrn [90] hit enter. forw [20] rtrn [90] Type in hide hit enter. hide Using the again Command You can use the again command to make the computer do the hard work. To use the again command first clear the screen using the cs command and show the turtle. cs Type in cs show hit enter. cs show Type in agn [4] forw [20] rtrn [90] hit enter agn [4] forw [20] rtrn [90] You now have a box on the screen. Page 4 Using the Faster command If speed of the drawing seems slow there is a way to speed the Turtle up using the F command. First clear the screen. F Type in cs hit enter cs Type in F agn [4] forw [20] rtrn [90] hit enter. F agn [4] forw [20] rtrn [90] This is the fast mode for the Turtle. Using the Pause Command If you wish to have the Turtle stop and wait you may use the the pse command. The pse (pause) command will stop the turtle and wait pse pse for a key to be pressed before going on the next command. To use the pse command first clear the screen - pse Type in cs hit enter cs Type in forw [30] pse rtrn [90] forw [20] hit enter forw [30] pse rtrn [90] forw [20] The turtle will go forward 30 spaces and wait now hit any key on the key board. The turtle will now turn and go forward 20 spaces and stop. Switching the Background color To switch the background color use the B command. B Type in B [3] hit enter B [3] Type in B [0] hit enter B [0] There are 0 to 15 background colors that you can use with a CGA. To reset to the default settings Type in cs hit enter cs The Repeat Command The Repeat command will repeat all the commands following it. The repeat command has to control keys they are the p key and the s p s key. When the repeat command is running hitting the p key will p pause the turtle hitting any key but the s key will continue the s Repeat command. If you hit the s key the turtle will stop. to use s the repeat command- Type in Rept rtrn [93] forw [11] hit enter Rept rtrn [93] forw [11] To pause the repeat command hit the the p key. p (Note do not hit the enter key) To continue the repeat hit the spacebar. (Note do not hit the enter key) To stop the repeat - Hit the p key then hit the s key. p s (Note do not hit the enter key). Type in cs hit enter cs To Enter Text on the screen To enter text on the screen use the T command. To use the text T command- Type in T [2] Hello There , hit enter T [2] Hello There , The number in the brackets is the line number to write the text. The message you wish displayed on the screen must end with a comma. Page 5 Creating your own programs or commands JEM allows you to create your own commands using the commands you have be shown. To create your own commands Type in expl hit enter expl Type in tell hit enter tell Type in Rightbox= F agn [4] forw [30] rtrn [90] ; hit enter Rightbox= F agn [4] forw [30] rtrn [90] ; The screen will now be back with the turtle and the command line. Type in Rightbox hit enter. Rightbox The turtle will have drawn the box. Listing your own commands Jem allows you to list your commands that you have created by using the the show command. To list your commands - show Type in expl hit enter expl Type in show hit enter show Type in all hit enter all Jem will now list all the commands or words in memory. Forgetting a command you have created Jem allows you to forget or get rid of commands that you do not want or simple do not work as planned. To use the forget command- forget Type in expl hit enter expl Type in forget hit enter forget Type in Rightbox hit enter Rightbox Hit enter Hit enter The command Rightbox is now gone. Page 6 Loading Files To load a file use the G command to use the the get file command- G Type in G hit enter G You will now be asked for the file name - Type in jem.dat hit enter jem.dat (Note if JEM.DAT has been removed from your disk you will get a error comment) Type in expl hit enter expl Type in show hit enter show Type in all hit enter all Hit the enter key until you get the command line back. When the Turtle and the command line return - Type in window hit enter window You now have a window on the screen. List the commands again and try some of the words listed in jem.dat Saving Files If you use the expl command during a session when you enter the expl end command Jem will ask you if you wish to save the word file if end you answer yes you will be asked for the name you wish to give the file. Or you may use the the Save command to use the the save Save command. Type in S hit enter S You then be asked to give a file name Type in Myfile.dat hit enter Myfile.dat Chaining Files JEM allows you chain files and commands to use this command you must know the file name and the first command you wish to execute in that file. Type in Do "jem.dat window" hit enter Do "jem.dat window" Jem will load the file jem.dat and execute the command window. jem.dat The Do command can be used to load files also to use as file Do loader only see page 9. Auto Run JEM Jem allows you to create an auto run file or an auto load file to use the auto feature. You must use the file name jem.run rename or jem.run create a file with this name. To use the the auto run feature the word or command startup must be in the jem.run file. The command startup startup can be defined as what ever you wish.(See page 9) Page 7 Variables Jem allows two variables they are var1 and var2. To set the value var1 var2. in the variables - Type in s [var1=1] hit enter s [var1=1] Type in s [var2=5] hit enter s [var2=5] To add to the current value of the variables Type in s [var1+2] hit enter s [var1+2] (this will add 2 to the current value of var1) var1 Type in s [var2+3] hit enter s [var2+3] (this will add 3 to the current value of var2) var2 To subtract to the current value of the variables Type in s [var1-2] hit enter s [var1-2] (this will subtract 2 from the current value of var1) var1 Type in s [var2-3] hit enter s [var2-3] (this will subtract 3 from the current value of var2) var2 To use a variable - Type in forw [var1] turn [var2] hit enter forw [var1] turn [var2] Screen wrap ON or OFF The screen normally wraps around that is to say that the turtle if it goes off the top of the screen it will appear at the bottom of the screen. You can turn the the wrap off if you wish that means the turtle will not appear at the bottom of the screen if the turtle runs off the top of the screen. The command to turn the wrap off is nwrp to turn the wrap on the command is wrap. nwrp wrap Page 8 To print out JEM's display turn the command line off,turn your printer on, hit the print screen key. JEM is language similar to the computer language FORTH , user words or commands may definded using the pre-defined commands and/or user defined commands to create more commands. Load the file JEM.DAT to see examples of user created commands. Chaining of files the user can chain any number of files to each other. The Auto run feature must have the JEM.RUN in the same directory as JEM.COM and the word startup must be used in the file startup JEM.RUN to start the auto run feature. To see how the auto feature works rename the file JEM2.DAT as JEM.RUN the load JEM. There is a small demonstration command in that file. User defined commands can be repeated in the same data file but but JEM will use the first definition only. The same word can be defined in a different file as a different command. User defined commands must be longer than five (5) characters in length for JEM must be longer than five (5) to use them. When using the ag (again) command care must used not to nest the ag the again command. Example of a nested command is ag [5] forw [10] ag [5] forw [10] ag [4] forw [10] rtrn [3]. ag [4] forw [10] rtrn [3]. To use the Do command to load files only simply do not give the Do only command a word to execute. Example of a file load using the the Do commmand. Do Type in Do jem.dat hit enter Do jem.dat Jem will load the file and return to the command line. Also a user defined command can call itself if you do this JEM will go in to endless loop. You can try Ctrl c to stop JEM but you may need to shut the system off to end the loop. Look at the JEM.DOC for addition information see next page for command abbreviations. Page 9 Jem basic commands can be shorten to one character to save time and space when the user creates their own commands here is a list of the shorten commands. Function Command Short Command Moving the turtle forward forw [spaces] f [spaces] Moving the turtle backwards back [spaces] b [spaces] Clear screen cs c Turn to a compass point turn [angle] t [angle] Hide the turtle from view hide h Show the turtle show s Turtle pen up upen u Turtle pen down dpen d Switch line colors Clr [number] C [number] Switch to Palette 1 1 1 Switch to Palette 2 2 2 Command line on Line L Command line off Off O 40 Chars per line(default) med m 80 Chars per line Hi H Exiting JEM end end Right turns rtrn [angle] r [angle] Left turns ltrn [angle] l [angle] Again x times agn [times] a [times] Faster command Fast F Pause wait foe keypress pse p Seting Background Color Back [number] B [number] Repeat Command Rept R Put text on screen T [line] here , T [line] here, Get a data file G G Get a data file Do filename D filename Save a data file Save S Get file Do a command Do file command D file command Screen wrap on wrap w Screen wrap off nwrp n Variable # 1 var1 var1 Variable # 2 var2 var2 Explain to Turtle explain exp Page 10 The following page will let you try some user defined commands in the data file JEM.DAT to see how the commands work. You can get a print out of the file JEM.DAT to look at by going to DOS put the JEM disk in the disk drive. At the DOS prompt- Type in copy jem.dat prn hit enter copy jem.dat prn After the printer is done load the JEM program at the DOS prompt - Type in jem hit enter jem This page has a number of commands in the JEM.DAT file the user can try and look at. First load the data file jem.dat- Type in D jem.dat hit enter D jem.dat Type in R shapes hit enter R shapes Jem will draw a number of shapes on the screen Type in cs R shapes2 hit enter cs R shapes2 Jem will draw some more shapes on the screen To see the difference in drawing speed using the Repeat command try this Type in cs shapes2 hit enter cs shapes2 When the turtle is finshed try the same word using the Faster command. Type in cs F shapes2 hit enter cs F shapes2 There is a noticeable difference in drawing speed. You can use the turtle to draw letters also try Type in cs F startwrite hit enter cs F startwrite Now you can try some of the other words in the JEM.DAT file. Try creating some words try Type in expl hit enter expl Type in tell hit enter tell Type in myword1= cs F startwrite ; hit enter myword1= cs F startwrite ; Get back to the command line and the turtle on the screen then - Type in myword1 hit enter myword1 Try creating your own words on your own now. Page 11 Index Page 1 Command line, help command Page 2 Moving the Turtle forw , back commands Page 2 Clearing the screen cs command Page 2 Turning the Turtle turn command Page 3 Turtle on or off hide,show command Page 3 Drawing lines penup pendown command Page 3 Centering the Turtle gohome command Page 3 Switching line colors Color command Page 3 Color Palettes 1 , 2 commands Page 3 Command line off Off Line command Page 3 80 ,40 Chars pre line Hi ,Med command Page 4 Ending a Jem session end command Page 4 Drawing a simple Box Page 4 Right turn command rtrn command Page 4 Left turn command ltrn command Page 4 Using the rtrn command Page 4 Using the again command agn command Page 5 Using the Faster command F command Page 5 Using the Repeat command R command Page 5 Switching the Background color B command Page 5 Using the Pause command P command Page 5 Using the Text command T command Page 6 Creating Commands Page 6 Using the explain command expl command Page 6 Using the list command show command Page 6 Forgetting a command forget command Page 7 File handing Page 7 Loading a data file Get command Page 7 Auto command excute Do command Page 9 Loading a data file Do command Page 7 Saving a data file Save command Page 7 Automatic load and run of JEM Page 8 Variables Page 8 Setting the variable value Page 8 Addition with the variables Page 8 Subtraction of the variables Page 8 Screen wrap on or off Page 8 Using nwrp command Page 8 Using wrap command Page 9 Chaining data files Page 10 Basic Command Short hand Page 11 Using the tell command Page 11 Creating commands Page 11 Practice using commands Page 12 Page 13