(e.g. you can directly execute a Scheme expression in the middle of editing it)and it very important that you become comfortable editing and working in Edwin Edwin is virtually identical to Emacs. Even if you are familiar with Emacs, you will find it helpful to spend about 15 minutes going through the on-line tutorial, which you start by typing c-h followed by t (c-h means"control-h": to type it, hold down the CTRl key and then type h. Then release the Ctrl key before typing t. You will probably get bored before you finish the tutorial, but at least skim all the topics so you know what's there You will need to gain facility with the editor in order to complete the problem sets and projects. To get out of the tutorial, type c-x k Return, which will kill the buffer General Emacs commands For reference information on using Emacs, see the MIT server, which contains links to a reference card for emacs and more extensive documentation on emacs There are a few Edwin specific commands, you can see many of them by typing c-h m at the top level of Edwin. Below we discuss some of the commands you are likely to use as you interact with Scheme and Edwin Files and buffers Edwin allows you to read and edit existing files(c-x C-f filename), and create and write files(c-x C-w filename or c-x C-s). The text within these files is contained in Edwin objects called"buffers". The name of the current buffer can be found at the base of the edwin window. Notice that Edwin starts up in a buffer called *scheme*.What distinguishes the scheme buffer from other buffers is the fact that connected to this buffer is a Scheme interpreter(more about how to activate the interpreter later!) One could simply type all one's work into the *scheme*buffer, but it is usually better to store versions of your code in a separate buffer, which you can then save in a file. The most convenient way to do this is to split the screen to show two buffers at once-the scheme* buffer and a buffer for the file you are working on. You will need to know how to split the screen(c-x 2)and how to move from one half to the other(c-x o). Choose a filename that ends in. scm for your code buffer, and then type c-x c-f filename(for ole ojowork. scm). The half of the screen your cursor is in be a buffer for this new file. You can type in this buffer and evaluate expressions in this buffer(more on this in the next section ) The results of expression evaluation will appear in the *scheme* buffer. If an error occurs during evaluation you must go to the *scheme* buffer to deal with the error In addition to the *scheme* buffer, edwin also provides a special read-only buffer called t* buffer which is automagically maintained and keeps a history of your this buffer type c-x b *transcript*. You can go back to any buffer with the c-xb 6 p interactions with the Scheme evaluator. You can extract pieces of this buffer to documen examples of your work for projects(see the c-space, M-w, and c-y commands). To go(e.g. you can directly execute a Scheme expression in the middle of editing it) and it is very important that you become comfortable editing and working in Edwin. Edwin is virtually identical to Emacs. Even if you are familiar with Emacs, you will find it helpful to spend about 15 minutes going through the on-line tutorial, which you start by typing C-h followed by t. (C-h means “control-h”: to type it, hold down the CTRL key and then type h. Then release the CTRL key before typing t.) You will probably get bored before you finish the tutorial, but at least skim all the topics so you know what's there. You will need to gain facility with the editor in order to complete the problem sets and projects. To get out of the tutorial, type C-x k Return, which will kill the buffer. General Emacs commands For reference information on using Emacs, see the MIT server, which contains links to a reference card for Emacs and more extensive documentation on Emacs. There are a few Edwin specific commands, you can see many of them by typing C-h m at the top level of Edwin. Below we discuss some of the commands you are likely to use as you interact with Scheme and Edwin. Files and Buffers Edwin allows you to read and edit existing files (C-x C-f filename), and create and write files (C-x C-w filename or C-x C-s). The text within these files is contained in Edwin objects called “buffers”. The name of the current buffer can be found at the base of the Edwin window. Notice that Edwin starts up in a buffer called *scheme*. What distinguishes the Scheme buffer from other buffers is the fact that connected to this buffer is a Scheme interpreter (more about how to activate the interpreter later!). One could simply type all one's work into the *scheme* buffer, but it is usually better to store versions of your code in a separate buffer, which you can then save in a file. The most convenient way to do this is to split the screen to show two buffers at once – the *scheme* buffer and a buffer for the file you are working on. You will need to know how to split the screen (C-x 2) and how to move from one half to the other (C-x o). Choose a filename that ends in .scm for your code buffer, and then type C-x C-f filename (for example, C-x C-f myproj0work.scm). The half of the screen your cursor is in will now be a buffer for this new file. You can type in this buffer and evaluate expressions in this buffer (more on this in the next section!). The results of expression evaluation will appear in the *scheme* buffer. If an error occurs during evaluation you must go to the *scheme* buffer to deal with the error. In addition to the *scheme* buffer, Edwin also provides a special read-only buffer called the *transcript* buffer which is automagically maintained and keeps a history of your interactions with the Scheme evaluator. You can extract pieces of this buffer to document examples of your work for projects (see the C-space, M-w, and C-y commands). To go to this buffer type C-x b *transcript*. You can go back to any buffer with the C-x b command