What Is User Interface?

"The iPhone ... is a line of smartphones designed and marketed by Apple Inc. It runs Apple's iOS mobile operating system. ...
The user interface is built around the device's multi-touch screen, including a virtual keyboard. The iPhone has Wi-Fi and can connect to many different cellular networks, including 1xRTT and GPRS (shown as a circle on the status bar), EDGE (shown as a capital E on the status bar), UMTS and EV-DO (shown as 3G), a faster version of UMTS and 4G (shown as a 4G symbol on the status bar), and LTE (shown as LTE on the status bar). An iPhone can shoot video (though this was not a standard feature until the iPhone 3GS), take photos, play music, send and receive email, browse the web, send texts, GPS navigation, tell jokes, record notes, do mathematical calculations, and receive visual voicemail. Other functions — video games, reference works, social networking, etc. — can be enabled by downloading application programs (‘apps’); as of October 2013, the App Store offered more than one million apps by Apple and third parties." [iPhone. Wikipedia]
The example "iPhone OS (iOS) graphic user interface (GUI) - Standby mode" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Graphic User Interface solution from the Software Development area of ConceptDraw Solution Park.

The vector stencils library "Apps icons" contains 24 icons of iOS 8 / iPhone 6 applications: Messages, Calendar, Photos, Camera, Weather, Clock, Maps, Videos, Notes, Reminders, Stocks, Game Center, Newsstand, iTunes Store, App Store, iBooks, Health, Passbook, Settings, Phone, Mail, Music, Safari.
Use it to design iOS 8 apps GUI prototypes and iPhone 6 applications user interface sketches and mockups.
"iOS 8 is the eighth major release of the iOS mobile operating system designed by Apple Inc. as the successor to iOS 7. It was announced at the company's Worldwide Developers Conference (WWDC) 2014 on June 2, 2014 and will be released on September 17, 2014.
A new app named Health and a corresponding framework named HealthKit will be available. Siri will support hands-free activation and music identification using Shazam. Voice and video messages will be automatically deleted unless the user saves them for future reference. Interactive notifications will let the user respond to texts without leaving the app they are currently using." [iOS 8. Wikipedia]
The example "Design elements - Apps icons" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the iPhone User Interface solution from the Software Development area of ConceptDraw Solution Park.