With Squeak you can save or commit your changes within a session and, if you want, you can then save them between sessions.
A session begins with starting Squeak and ends with quitting Squeak. Unless you save your image before you exit, Squeak will rememeber none of your changes.
You save an image by bringing up the World Menu and selecting the "Save", "Save as..." or "Save and Quit" action.
When you save your image, if you have a Transcript Window open, you will see a message like: "—-SNAPSHOT—-#(30 November 2003 7:50:19 pm) Squeak3.7a-5566.image priorSource: 14011317"
Within a session, you will often need to "accept" or save some change. For examle, after making some change within a Browser you must accept the change (commit the change at least for this session)before it will take effect. If you change a method and then go to another method, without accepting the change, you will get a warning dialog.
You accept a change using the alt-s (for Windows) or alt-c (for Mac)key combination (cmd-s on the Mac will accept, cmd being the apple key). Or bring up the context menu (right click) and select the "accept (s)" action.
When you accept a change, you do not generally get a confirmation. (The first time you make a code change, you get asked to enter you initials.)
Do you have to accept a change to a Workspace before you can evaluate an expression? No.
Do you have to accept a change to a Class before it will have an impact on evaluating an expression? Yes.