For this lab it's better to log on to the remote host with an X11 connection - either from a Linux machine (locally) or from a mac with the optoin -XY for ssh, or from putty using Xming. If you work from putty without Xming, remember F10 as the key that gives you access to the menus.

Note. The Meta key is the Alt key under Linux or Windows/putty. Under MacOs it should be the Command key. If the Meta commands don't work properly, click on the X in the dashboard , go to X11 -> Preferences, click on the Input tab, and unselect the Enable key equivalents under X11.

Ex. 1 This exercise is about the Emacs editor. Connect to one of the Linux computers using the ssh command with the option -X -Y (or -XY). Open the emacs editor with the command emacs &. If you do this from home using putty, to access the menu you have to use the special key F10.

• Create a new buffer with the command Ctrl-x Ctrl-f (the same as for opening an existing file). In the dialog at the bottom of the window (in the minibuffer) enter the name "my_eq.cc". The minibuffer should tell you it's a new file.
• In the browser click on the following link:
  eq.cc
  Copy the content of this file from your web browser into the new file you have just created. For this, from a Mac, select the text in the broswer, copy it with Cmd-C, then paste it by holding the option (alt) key down, then clicking in the emacs window, or use Paste from the Edit menu. If you are in a Linux environment, select the text in the browser with the mouse (not the Ctrl-A), then paste it in the editor with Ctrl-y. If you are in Windows using putty, select the text and copy it (Ctrl-c), then right-click in the terminal to paste it.
• Save the file with Ctrl-x Ctrl-s.
  
  
• Indentation
  Notice that the program is badly indented. Select the entire code if your window interacts with the mouse (on any system but Windows with Putty). If you're in a text-only terminal like putty, go to the begining of the main and set the beginning of the selected region mark on this point with Ctrl-space. Move down to the end of the program (not including the comment). The entire code should be highlighted.
• From a Mac or Linux environment, from the C++ menu select Indent line or region. If you work in a putty terminal, press the function key F10, followed by a lowercase c to select the C++ menu, the uppercase I to select the option Indent line or region. Your program should now be correctly indented.
  
  
• Copy-Paste
  Select the code from line 24 to line 33 (including 33) as you did for the previous part. Copy this region with Meta-w. Paste it in the code after line 33 (before return 0) with Ctrl-y twice.
• Undo one of the pasing operations with Ctrl-_ (Ctrl shift minus).
• In the new code that you added replace the variable a with b and the other way around. This should compute the solution for

  bx+a = 0

• Compilation
  To compile the file run the command compile by typing Meta-x then typing compile directly at the botton of the window (minibuffer) where the M-x is displayed, and then pressing return. The editor will ask for a compiling command. By default it will propose "make -k". Delete this and type

  g++ my_eq.cc

  instead.
• The program will not compile because there are some compiling errors. Hide the compilation result by typing Ctrl-x 1. Go to line 18 by pressing

  Meta-g g

  followed by return, and then the line number. Replace the COUT symbol on this line with cout.
  
  
• Search - Replace
  Note that there might be other occurences of COUT in the file. To make sure you replace all of them, from the Edit menu, choose Replace, then Replace String... (or Meta-%). The minibuffer should say "Query replace: ". Enter the misspelled COUT and enter. It should now say "Query replace COUT with: ". Enter cout. The editor will highlight every entry of COUT one by one. To replace an entry you must type the spacebar or 'y', and to skip an entry you should enter 'n'. After replacing 2 of them, type '!' to replace all of the remaining occurrences of COUT. Save this file.
• Compile the file again (the Compile command can also be found in the Tools menu). This time there should be no error and the result will be the file a.out. Verify in the terminal that this file was created.
  
  
• Execution
  Create a simple text file called "eqin". In this file write the two numbers a and b, each on a line. Save the file and close it (Ctrl-x k then return). Run the program by invoking the shell command execution first (Tools menu -> Shell Command or Meta-!) and then typing

  a.out < eqin

  The editor should display the result of the program execution. Close that window with Ctrl-x 1.
• In the file "my_eq.cc", delete the last comment containing the output of the program. Replace the name at the top with your name. Save this file.
  
  
• Spell checking.
  Select (highlight) the entire comment at the beginning of the program. From the menu Tools choose Spell Checking, then Spell Check Region. Do not correct the name of the course or my name (space to leave unchanged). Correct all of the other words that are misspelled.
  
  
• Wrapping.
  Place the cursor anywhere on the long line in the comment at the top of the program. Wrap this line with Meta-q.
• Save this file. You will have to upload it to Oncourse.
  
  
• Create a new file called lab4.txt.
• Display the named colors available for Linux and copy them to the file lab4.txt. For this, from the Edit menu follow with Text properties, the Display colors. Choose two of them that you like, then go back to the terminal (or hit Ctrl-z from putty) and run another emacs editor, but this time with the options
  emacs -bg color1 -fg color2
  For example, if I chose the color1 to be RoyalBlue3 and the color2 to be SlateGray1, I would run the command the following way:
  emacs -bg RoyalBlue3 -fg SlateGray1
  Note the difference between the two emacs windows. Open the file "my_eq.cc" in the second window with the command Ctrl-x Ctrl-f to see how the -fg option (foreground color) has affected the text display. You can close this second window now (and if you stopped the other emacs window with Ctrl-Z, go back to it with the command fg)
• Copy the command that you have executed to open the second emacs window in the file lab4.txt that should be the active buffer in the first emacs window.
• From the Tool menu select Calendar. From the Holidays menu, display the holidays for the window (which should be Aug-Oct), then copy them to the file lab4.txt.

Submit. Upload the files lab4.txt and my_eq.cc to Oncourse, Assignments 2, Lab 4. If you work remotely, then you may have to transfer the file to your local computer first by sftp (see How To SFTP)