How Applications Work in OS X and Other Various Questions

I am new to Mac.  Like it a lot, but having trouble getting the some of the UI's paradigms.

-From a technical perspective, what is an "application" to the OS and where does its file reside?  I see there is an Applications folder with applications in it, but clearly they don't need to be in there to run.  What are the "rules".

-When I download an application from the web, something gets "mounted" on my desktop.  What is this item supposed to represent?  Why does this only happen in the Desktop?  If I launch a program from the Applications folder this doesn't seem to happen.

-When I install a new program I've DLed, a window pops up and tells me to drag the application icon into the Applications folder.  What am I doing when I do this?  Are any changes made to the system other than copying files to the Applications folder?  What am I supposed to so with the readmes and other files that pop up in that box with the application icon?  Are the also stored with the application "package" that gets written to the Applications folder, or am I supposed to file them away somewhere?

-When these desktop-launched application files are exited, sometimes I can't "eject" them until I reboot.  Why is this, and why am I "ejecting" it in the first place?  Related to the first question.

-Is there something like the Task Manager in OS X that allows me to see all of the running processes?

-Is there a way I can see what applications the OS is supposed to execute when it boots up?

-Is there a way to cycle through open windows (like Windows' Alt-Tab)?  I realize Cmd-Tab approximates this functionality in Mac, but it cycles only through open applications, not windows.

That'll do for this round.

Cheers,

Mike



shachoAsked:
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slyongCommented:
- An application to any operating system is just a binary.  Normally for OS X, we like to put the application into the Applications folder.

- In OS X its a dmg file, which basically is  like an ISO image.  If you double clicked on a dmg file, it is mounted.  OS X does some trick that all mounted images are shown on the Desktop.

- When you drag the file into the Applications folder, it gets copied over nothing else.  When you launch the application, it will do its things like write some files into the preferences folder, etc etc...

- When you "exit" an application, did you use Apple-Q to quit the program?  A program in OS X doesn't "exit" properly by just closing the windows.  That's why you can't eject the mounted image because the program is still running.

- Press Apple-Option-Esc

- There are a few ways to startup applications during boot up, you might want to read it here: http://www.osxfaq.com/Tutorials/LearningCenter/HowTo/Startup/index.ws

- hmm.. not sure about cycling through windows... How about Expose.. http://docs.info.apple.com/article.html?artnum=304786
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Eoin OSullivanConsultantCommented:
-From a technical perspective, what is an "application" to the OS and where does its file reside?  I see there is an Applications folder with applications in it, but clearly they don't need to be in there to run.  What are the "rules".
Applications ... USUALLY reside in the Applications folder but will USUALLY work from any folder or Volume which the currently logged-in user had READ access to.
Nearly all applications will store their settings/preferences and any infomation that needs to be written/updated in the Users/Library folder and certain folders inside this such as Preferences.
If a program is to be available to ALL users it may also put data files in the /Library folder at the root of the system (during install it will usually prompt for administrator username and password in order to do this)

-When I download an application from the web, something gets "mounted" on my desktop.  What is this item supposed to represent?  Why does this only happen in the Desktop?  If I launch a program from the Applications folder this doesn't seem to happen.
The "mounted" file is usually a DMG or disk image file .. think of it like a custom ISO or disk image.  The App developer can create a custom volume with the application or installer and associated files.  Once mounted you can often RUN the application from the mounted DMG .. however when you move the  DMG Image to the trash the application will no longer be available.  That is why most developers advise you drag the program to the Applications folder.
Double-clicking the DMG will re-mount the image and allow you to run the Application.
Even when you run an Application from a disk image .. Preference and Settings files will be saved in your Users/Library folder.

-When I install a new program I've DLed, a window pops up and tells me to drag the application icon into the Applications folder.  What am I doing when I do this?  
See previous question

- Are any changes made to the system other than copying files to the Applications folder?  
NO.. Untl you open the Application the first time when it will create additional preference and settings files.

- What am I supposed to so with the readmes and other files that pop up in that box with the application icon?  Are the also stored with the application "package" that gets written to the Applications folder, or am I supposed to file them away somewhere?
The readme files are usually optional.  The application .. if it comes with Help files etc will usually install these the 1st time it is run.
Files on the DMG Image are usually optional or for additional information

-When these desktop-launched application files are exited, sometimes I can't "eject" them until I reboot.  Why is this, and why am I "ejecting" it in the first place?  Related to the first question.
See previous questions ... you cannot eject sometimes because a process started by that Application may still be running

-Is there something like the Task Manager in OS X that allows me to see all of the running processes?
Yes, it is called Activity monitor and resides in your Applications/Utilities folder

-Is there a way I can see what applications the OS is supposed to execute when it boots up?
YES, Activity Monitor will show you processes owned by user, and system
This is the overview of the system startup sequence
http://www.kernelthread.com/mac/osx/arch_startup.html
http://developer.apple.com/documentation/MacOSX/Conceptual/BPSystemStartup/Articles/BootProcess.html
also
User programs (a bit like Startup Items in Windows) are set in the System Preferences/Accounts/Login Items dialog

-Is there a way to cycle through open windows (like Windows' Alt-Tab)?  I realize Cmd-Tab approximates this functionality in Mac, but it cycles only through open applications, not windows.
Command-`      Cycle through windows in application or Finder (if more than one window is open)
OSX keyboard shortcuts - http://docs.info.apple.com/article.html?artnum=75459
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ahoffmannCommented:
> -Is there a way I can see what applications the OS is supposed to execute when it boots up?
hit Apple-V while booting, then you see the console (there exists a plist entry too, to make this the default behaviour)
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shachoAuthor Commented:
Very helpful!  Thanks a lot.

>Command-`      Cycle through windows in application or Finder (if more than one window is open)
This seems to work only for the active application - and only for non-minimized windows.  Is there anything that can cycle through all apps and all windows in any state (this is how Alt-Tab works in Windows)?

Mike

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ahoffmannCommented:
what is an "app" in your definition? a daemon also, I doubt.
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shachoAuthor Commented:
Not all system processes, just open windows (minimized to dock or otherwise) for applications with user interfaces, so Safari, Firefox, GarageBand, TextEdit, etc.  So a tab-through session might look like this:
Word - MyDocument1.doc  ->
Word - MyDocument2.doc  ->
Safari - www.goolge.com  ->
Safari - www.yahoo.com  ->
Safari - <blank window>  ->
Word - MyDocument1.doc

Mike
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ahoffmannCommented:
AFAIK this is only possible if each of this windows is its own application, but not if one application has more than one window.
Mac's modern OS X Quartz is not like (century-old) X :-/
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shachoAuthor Commented:
Oh well.  Thanks for your input.

Mike
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Eoin OSullivanConsultantCommented:
Mike / shacho .. Sorry but I have UNACCEPTED your selected answer for a few reasons
1. You may not be aware but you can allocate points across several different replies rather than allocating ALL the points to one answer.
2. Considering you asked 8 sub-questions and several respondents answered some and most of your questions it is not fair to allocate ALL points to ahoffman for a partial answer to one question.
3.  ahoffman is wrong as there IS a way to cycle between ALL open windows .. either via special keyboard shortcuts or using an add-on for OSX called Witch (http://manytricks.com/witch/)
Read more here
http://www.macworld.com/article/60444/2007/10/windowcycle.html

Therefore please reconsider the allocation of points ..
See the section here on closing a question with multiple correct or partial answers
http://www.experts-exchange.com/help.jsp#hi331

Thank you for your understanding
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shachoAuthor Commented:
Man, my bad.  You're quite correct.  And believe me, I don't make that mistake.  Thanks for catching it.

Cheers,

Mike

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ahoffmannCommented:
> .. there IS a way to cycle between ALL open windows
nice link eoinosullivan, I'm learning too ;-)
Anyway, it does not describe how to cycle through windows using the application tab list (command-tab) 'cause this only shows one instance odf an application.
Anyway ^F4 should do the trick, while Exposé's ^F9 and ^F10 reqires to select the proper application first. Please correct me if I'm wrong.
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