Apple's approach, in general, is to make things easy for the consumer (with varying results
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But a standard install takes 25 GB five or take, leaving you with about 100GB to add apps and data. For browsing, email, streaming - more than enough. Things like iCloud link your app downloads and purchases such that you can get them again, and update through the "App Store" on your Mac. Note that your system username/password and your iCloud username/password don't have to be the same. And while it's pretty easy to change you system name/password, it's much harder to do so on your iTunes/iCloud username password.
Lots of tips and tricks - and lots of people here on MR to help. Here's two of my favorites:
- Command-tab switches between open apps (just like Windows!)
- If you're used to a Start Button way of doing things, you can replicate the same thing on your Mac.In the Finder window, in the left side, select Devices-YourMac. Then, Drag the Applications folder to the Dock. It has to be to the right/bottom. Right click the Apps folder in the doc, and check Sort by Name, Display as Folder, View as List.
Bonus tip: nearly everything is customized in Preferences. Under Finder Preferences, you can select what you can see in the Finder (Explorer) windows. Also, go to System Preferences - Track Pad - Point and Click and elect Secondary Click (click in right corner) if that's what you want, or other options.