The first glimmer of Apple's resurgence as a major competitor in computing, the iMac splashed onto the scene in 1998, a translucent-colored all-in-one computer with a built-in 15-inch CRT display. Since then Apple has continuously evolved and changed the iMac to keep up with changing performance needs and Apple's own design strategies, and we're left today with a gorgeous, powerful system that graces the upper echelon of performance in the Macintosh product lineup.
The iMac has always been a vanguard of innovation for Apple. It was the first Mac to include USB instead of a serial interface, and the first Mac to get rid of the floppy drive. It eventually traded in its CRT for an LCD, adopting a "flower pot" design that articulated the screen away from the body using a hinged arm.
Eventually the all-in-one design returned, and in 2012 Apple radically redesigned the iMac again, making it razor thin and getting rid of its internal optical drive. That's essentially the same design we have today.
The iMac comes in two sizes: 21.5 and 27 inch. The 21-inch system sports a 1920 x 1080 pixel resolution display, while the 27-inch features 2560 x 1440 pixels. Both screens employ backlit LEDs with In Plane Switching (IPS) technology, which improves response time and enables a wider viewing angle.
The 21.5-inch iMac starts at $1099; for that you get a 1.4 GHz dual-core Intel Core i5 processor, 500 GB hard drive and Intel HD 5000 integrated graphics. $1299 gets you a 2.7 GHz quad-core Intel Core i5 processor and 1 GB hard drive. The 27-inch iMac starts at $1799 and offers a faster 3.2 GHz quad-core processor and better graphics (everything except the $1099 and $1299 21.5-inch models uses discrete Nvidia GeForce GT 7-series graphics processors; the $1299 model works with integrated Intel Iris Pro graphics instead).
In October 2014, Apple brought the Retina nomenclature to the iMac, introducing a 27-inch model equipped with a 5K Retina display for $2,499. It's the new iMac premium - faster, equipped with a 3.5 GHz quad-core i5 processor and an AMD Radeon R9 M290X graphics processor. It also comes standard with Thunderbolt 2 (twice the bandwidth of the original Thunderbolt) and a 1 TB Fusion Drive.
Regardless of whether you go large or small, the iMac comes by default with 8 GB RAM and a 1 TB hard disk drive; you can optionally configure it with more RAM, a faster processor or a larger hard drive. Performance mavens can opt for Solid State Drive (SSD) or Fusion Drive, which combines the 1 TB mechanism with SSD for faster overall performance.
The iMac was updated in the fall of 2013 with Intel Haswell microprocessors; Apple also added 802.11ac "Gigabit Wi-Fi" wireless networking support. Bluetooth 4.0 is supported, and either system comes equipped with dual microphones, stereo speakers, a headphone/optical digital audio output, SDXC card slot, four USB 3.0 ports, two Thunderbolt ports, a Gigabit Ethernet jack and a Kensington lock slot. Also included is Apple's standard Wireless Keyboard and Magic Mouse.
When it debuted the iMac was squarely aimed at consumers and schools looking for an inexpensive system that could get them online and work well as an all-around personal computer, but businesses and enterprises still stuck squarely with Power Macintosh models - more "serious" business machines.
Things have changed a lot in the intervening decade and a half. The iMac is now one of Apple's top-performing computers, a workstation that's more likely to be found on the desk of a content creator working with big digital photo files, video, multitrack audio, 3D rendering or any of the other myriad uses that demand a high-horsepower Mac.
The bottom line: These days, the iMac is the ultimate desktop computer for everyone and anyone who doesn't need the obscene horsepower of a Mac Pro.