Apple announced upgrades to its iMac and Mac Pro lineups, and introduced a new 27-inch Cinema Display.

iMac -- The iMac "Core i7" 4.0 27-Inch Aluminum (Retina 5K, Late 2015/Skylake) features a 14-nm "Skylake" Quad Core 4.0 GHz Intel "Core i7" processor (6700K) with fourindependent processor "cores" on a single chip, an 8 MB shared level 3 cache, 8 GB of 1867 MHz LPDDR3 SDRAM (PC3-14900) installed in pairs (two 4 GB modules), a 1 TB or 2 TB "Fusion Drive," and an AMD Radeon R9 M390 or AMD Radeon R9 M395 graphics processor with 2 GB of dedicated GDDR5 memory. It also has a built-in "FaceTime HD" webcam and stereo speakers.

The 21.5-inch and 27-inch models remain the standard form factors for the iMac, with the smaller model offered in three separate processor configurations, and the larger model offered in 3 as well. The base configurations and their respective configure-to-order options are as follows:

*21.5-inch ($1,699): 1.6 GHz Intel Core i5, Turbo Boost to 2.7Ghz, 1TB hard drive, Intel HD Graphics 6000 with 8GB RAM and 1920 x 1080 sRGB Display.

*21.5-inch ($1,999): 2.8 GHz Intel Core i5, Turbo Boost to 3.3Ghz, 1TB hard drive, Intel Iris Pro Graphics 6200 with 8GB RAM and 1920 x 1080 sRGB Display.

*21.5-inch ($2,299): 3.1 GHz Intel Core i5, Turbo Boost to 3.6Ghz, 1TB hard drive, Intel Iris Pro Graphics 6200 with 8GB RAM and Retina 4k 4096 x 2304 P3 Display.

*27-inch ($2,799): 3.2 GHz Intel Core i5, Turbo Boost to 3.6Ghz, 1TB hard drive, AMD Radeon R9 M380 with 2GB Video Memory, 8GB RAM (up to 32GB) and Retina 5k 5120 x 2880 P3 Display.

*27-inch ($3,099): 3.2 GHz Intel Core i5, Turbo Boost to 3.6Ghz, (or up to 4.2GHz i7), 1TB Fusion drive, AMD Radeon R9 M390 with 2GB Video Memory, 8GB RAM (up to 32GB), and Retina 5k 5120 x 2880 P3 Display.

*27-inch ($3,599): 3.3 GHz Intel Core i5, Turbo Boost to 3.9Ghz (or up to 4.2GHz i7), 1TB hard drive, AMD Radeon R9 M380 with 2GB Video Memory, 8GB RAM (up to 32GB) and Retina 5k 5120 x 2880 P3 Display.

First introduced in 2008, the MacBook Air originally represented Apple's first substantial re-entry into the subnotebook market in many years. Since it was first introduced, though, the MacBook Air became more powerful and capable and replaced the more "traditional" MacBook altogether in 2012. However, in 2015, the "regular" MacBook was re-introduced as an even smaller notebook than the MacBook Air.

What are all the differences between the "Early 2015" MacBook Air models? Which is the best choice for my needs?

Except for the display size and the size and weight differences, the standard "Early 2015" MacBook Air models -- the  MacBook Air - Core i5, 1.6, 11" (Early 2015), and the Core i5, 1.6, 13" (Early 2015) -- are pretty much identical to each another.

Likewise, the custom processor configurations -- the MacBook Air the Core i7, 2.2, 11" (Early 2015) and the Core i7, 2.2, 13" (Early 2015) -- vary from their respective stock models only by processor. 

However, there are some important external and internal differences. Additionally, as the models are so similar to each other (and earlier MacBook Air notebooks), identification details are particularly worthwhile, too.

*11-inch ($1,399): 1.6 GHz Intel Core i5, Turbo Boost to 2.7Ghz (or up to 3.2GHz i7), 128GB Flash drive, Intel HD Graphics 6000, 4GB RAM (up to 32GB) and Retina 5k 5120 x 2880 P3 Display.

Some times the hardest thing to find is some basic assistance to understand the keys and short cuts. Here is a really helpful list of just that. Dan Rodney’s Mac OS X Keyboard Shortcuts -- An amazingly comprehensive list, presented in an easy-to-read format.

Here is another very comprehensive list of Mac keyboard shortcuts for various applications.