Like the iPhone, with which it shares a development environment (iPhone SDK, or software development kit, version 3.2 onwards), the iPad only runs its own software, software downloaded from Apple's App Store, and software written by developers who have paid for a developer's license on registered devices. The iPad runs almost all third-party iPhone applications, displaying them at iPhone size or enlarging them to fill the iPad's screen. Developers may also create or modify apps to take advantage of the iPad's features. Application developers use iPhone SDK for developing applications for iPad. Around 1,000 new iPad apps were expected to be available at launch.
The iPad comes with these applications: Safari, Mail, Photos, Video, YouTube, iPod, iTunes Store, App Store, Maps, Notes, Calendar, Contacts, and Spotlight. The iPad syncs with iTunes on a Mac or Windows PC. Apple ported its iWork suite from the Mac to the iPad, and sells the Pages, Numbers, and Keynote apps in the App Store. Though these applications aren't as complete as their desktop counterparts and only have fair basic functionality. Although the iPad is not designed to replace a cellphone, a user can pair it with a Bluetooth headset and place phone calls over Wi-Fi or 3G using a VoIP application.