Editors' note: This post has been updated with information about iOS features up to the current release.
Apple's WWDC starts in about a month, and if Apple sticks to its usual schedule, we expect to hear an announcement for iOS 8 during the keynote. June will also mark the seventh anniversary of the iPhone, and it's easy to see much has changed in the OS since that first unveiling.
Back in 2007, when the first iPhone hit stores, the OS wasn't even called iOS. At the time, Apple said the phone was running a version of OS X, and was simply called the iPhone OS. This early operating system just had what we know today as the core apps -- basics such as Safari, Mail, Maps, Notes, and a few others. It's hard to believe, with how important the App Store is today, but it wasn't until iPhone OS 2.0 that the iTunes App Store was even introduced and still took a while to really get off the ground as app developers experimented with the new device.
A year later, iPhone OS 3.0 was released, and users began to get used to the idea that the smartphone operating system was an evolution that would continue to improve incrementally over time. The first iPhone had almost nothing beyond the fancy touchscreen interface, but starting with the name change of iOS 4, Apple slowly crossed off the items on our wish lists (while adding new features we hadn't thought of along the way).
Even so, Apple fell behind the competition which had features such as copy and paste, and, later, multitasking. With subsequent updates we finally got many of these features, but we had to wait while other smartphones were pulling ahead.
With WWDC only a month away, check out how it all began for the iPhone OS and the steps it took to get to where we are today. It's important to note I'm not covering every release here, instead showing the features added by the time the next major version was released.
iPhone OS 1.0 (initial release)
June 1, 2007
Initial release for the first iPhone
Offered apps include the basics like Mail, Messages, Safari, Maps, YouTube, and Calendar.
iPhone OS 1.0.1 - 1.1.4
Beginning in Sept. 2007
Improved EDGE and Wi-Fi reception
iTunes Wi-Fi Music Store
Customizable Home screen
Multirecipient SMS messages
Web clips (Creating a home screen icon that goes to a Web page)
Support for iTunes movie rentals
iPhone OS 2.0
July 1, 2008
Support for iPhone 3G
Support for App Store and third-party applications
Support for Microsoft Exchange
Support for 3G data and GPS
iPhone OS 2.0.1 - 2.2.1
Beginning in Sept. 2008
Google Street View with directions
"Double tap" shortcut brings you to the first Home screen
Significantly better battery life for most users
Faster installation of third-party apps
Improved accuracy of the 3G signal strength display
Genius playlist creation
iPhone OS 3.0
Copy and paste
MMS: Text messages with photos and videos
New app: Voice memos
Landscape mode in mail, text, and notes
Voice Control of phone and iPod (iPhone 3GS only)
Renting and purchasing of movies, TV shows, and audiobooks over the air
Find My iPhone feature for lost phones via MobileMe
In-app purchases now supported
iPhone OS 3.1 - 3.2
Beginning in Sept. 2009
App Store Genius
New premade ringtones available for purchase
Support for iPad (iPhone OS 3.2)
Home screens can be customized on iTunes 9
Fast-forward and rewind from headphones
Folders for organizing apps
Unified email inbox and threaded e-mail conversations
Improved security and business features
iBooks for iPhone, iPod Touch
100+ other fixes and features
Drops support for the original iPhone
iOS 4.1 - 4.3.5
Beginning in Sept. 2010
AirPrint wireless printing
Free Find My iPhone service
Assign unique tones to individual SMS senders
Support for Verizon
No longer backs up location data during sync
Support for iCloud and iTunes Match
iMessage replaces Message app
Systemwide Twitter integration
Siri (iPhone 4S only)
Notification Center and updated lock screen to include notifications
New app: Reader
New app: Reminders
New app: Newsstand, for reading magazines purchased through the App Store
Addition of a camera shortcut to the lock screen
Use the volume-up button to take photos
Game Center app adds support for turn-based network games
Genius Mixes and playlists for iTunes Match
Support for third-generation iPad
Updated camera app for third-generation iPad
Updated Camera shortcut from lock screen
New app: Apple Maps
Turn-by-turn navigation with voice
New app: Passbook, for storing boarding passes, coupons, loyalty cards, and more.
Siri updated to deliver better restaurant results, dictates Twitter and Facebook updates
Make FaceTime calls over cellular
Larger "Report a Problem" button in Maps.
New music controls on lock screen
Use Siri to buy movie tickets through Fandango
Complete design overhaul with flattened graphics affecting all core apps
AirDrop functionality added, letting you quickly send files to people nearby
App Store adds section for "Near Me" letting you see what apps are popular in your area
Camera app gets new design, burst mode, and live filters when taking shots
New Control Center lets you get to most used settings and other tools with a swipe
iTunes Radio debuts as part of the Music app for ad-supported listening
Multitasking gets a new look and lets apps update in the background
Spotlight accessible on any page of the home screen with a swipe downwards
Siri lets you hold down home button to talk or ask a question then release to get answer
New search box at the top of iTunes Radio for creating streams
Calendar displays event list within month view
Camera adds "HDR Auto" feature
What's next? (iOS 8)
Apple's iOS 8 will likely be released to the public this fall, but we won't know for sure what features the OS will have until Apple takes the stage at the WWDC keynote. Recent news hinted that we may not get many of the features that have been rumored in iOS 8, and instead will get some in the fall, and more in iOS 8.1, early next year. With that said, there have been several rumors surrounding Apple's latest iPhone OS.
One of the new additions, reportedly, is an app called Healthbook, which will focus on wellness through measuring steps taken in a day, caloric intake, blood sugar levels, and more, relying on third party apps and devices to gather the information (or perhaps sensors in the iPhone 6). Another rumor is that iTunes Radio will get its own app, which makes sense so you won't have to dig around in the Music app and can start listening much more quickly.
I've heard we're also going to see improvements to Apple's Maps app, with public transit information finally returning to the fold along with indoor navigation and augmented reality that will give you information about what you're looking at through the iPhone camera.
Siri is supposed to get an update as well, possibly integrating the music identifying technology you get with the popular Shazam app. Obviously, being able to simply ask "Siri, what song is playing?" is much easier than finding and opening Shazam then scanning for a song.
There are several other rumored changes in iOS 8 such as a more streamlined Notification Center, a revamped Voice Memo app, and several other upgrades, but there's no telling if all will make it in to iOS 8 or if Apple wants to wait to add them to iOS next year. One thing is certain: with a new iPhone presumably on the way, iOS 8 will probably have surprises nobody could have guessed, making this year particularly exciting for fans of iOS and the iPhone.