History

The original iPad was released April 3, 2010. Apple was one of the first producers to use an ARM based SoC (system-on-a-chip) in a tablet, which were previously used in Smartphones. The low power ARM chip gave the tablet very long battery life compared to laptops and competing Windows x86 tablets of at the time. It used a 9.7" 1024x768 very high quality IPS (in-plane switching) display that has far superior viewing angles to the cheaper TN (twisted nematic) displays used in most laptops in 2010. Apple incorporated their iOS mobile operating system that is also on the iPhone and iPod Touch. There were some glaring omissions with the original iPad, like a lack of cameras and multitasking. Developers could design apps specifically for the larger display. As of October 2013 there are 475,000 apps designed for the iPad (according to Apple) which compares to 1,000,000 iPhone apps (iPhone apps can be used on the iPad but won't look good due to the different aspect ratio and pixel count).

 

The iPad 2 came along on March 11, 2011. It beefed the SoC with the new A5 with a dual-core ARM A9 CPU, PowerVR SGX543MP2 GPU (which Apple stated as 9 times the performance of the original iPad), thinner (0.33" vs. 0.50"), lighter (1.325lbs vs. 1.5lbs), and for the first time came with cameras (front and rear). The iPad 2 had a completely new design which was less boxy and more curved at the edges. Along with this release Apple came out with an accessory they called the Smart Cover. The Smart Cover attached to the iPad 2 magnetically (which were both in the tablet and cover) so the cover auto aligned making it easy to put on and remove. The cover also automatically woke up the iPad when you opened it and put it to sleep when you closed it. They said they didn't want to cover their beautiful new design but obviously a screen cover does just that, only protects the screen and not the aluminum body of the iPad.

 

The 3rd gen iPad was released March 16, 2012. It lost the number designation and was just called iPad. The big change for this release was the high resolution retina display which upgraded the 132 ppi 1024x768 panel (in the iPad 1 & 2) to a 264 ppi 2048x1536 panel. The high resolution gave it four times the pixels of the previous two versions (786,432 vs. 3,145,728). Due to the huge GPU power required to run the retina display the tablet actually got a little thicker (0.37" vs 0.33") and heavier (1.427lbs vs. 1.325lbs). The majority of the increases likely coming from the huge 42.5Wh battery (the iPad 2 had a 25Wh battery) which was required to keep the same 10 hour battery life with the new power hungry SoC. 

 

The 4th gen iPad came on November 2, 2012. This was the first iPad to be released the same year as its predicesor and was only a 7.5 month span between 3rd and 4th gen release (versus the usual 11-12 months). Part of the reason for the early release is likely a combination of Apple wanting to update it to the new Lightning connector (replacing the 30-pin connector), release it along with the new iPad mini, and maybe they planned it that way. The 4th gen was also interesting because it used a custom CPU designed by Apple called Swift (but still used a GPU made by Imagination Technologies). Previous iPads used a complete ARM design. 

 

The original iPad mini came out November 2, 2012. It was Apple's response to low priced 7" Android tablets like the Kindle Fire HD and Nexus 7, and at the announcement Apple even did a screen area comparison of a tablet that looked exactly like a Nexus 7. Steve Jobs was very critical of 7" tablets and even called them "dead on arrival" and "tweeners." To Apple's credit technically they didn't make a 7" tablet but a 7.85" tablet (that's the actual display size, which Apple rounds up to 7.9" for simplicity and marketing). The iPad mini has the advantage of more screen area but a lower pixel density compared to its 7" Android competitors. The original mini did not include a retina display but the same 1024x768 resolution as the iPad 1 & 2 (except in a smaller 7.85" panel). The iPad mini received good reception from the public but had a few downsides in its 1st gen. It used the over 1.5 year old A5 SoC (same as the iPad 2, iPhone 4S, and iPod Touch 5th gen), instead of the newer A6 in the iPhone 5 or A6X in the iPad 4.

 

The 5th gen iPad was released on November 1, 2013. Apple renamed it the iPad Air because it's 20.2% thinner (7.5mm vs. 9.4mm) and 28% lighter (1.034lbs/469g vs. 1.437lbs/652g, Wi-Fi models) than the iPad 3 and 4. Now a full size iPad is finally lighter than the iPad 2 (1.325lbs/601g). So there is no longer the retina thickness/weight compromise of the 3rd and 4th gen.

 

The 2nd gen iPad mini was silently released November 12, 2013 and now has a retina display and the newest A7 SoC, but carriers a very high price tag of $399 ($70 increase from the previous gen) compared to $229 for the Nexus 7 2013 and Kindle Fire HDX 7".