Use apps such as Androidsoft Assistant and SyncDroid to back up Android contacts to a computer. MobileGo's Androidsoft Assistant is available at AndroidPhoneSoft.com, while SyncDroid is available at Sync-Droid.com, as of November 2015. Whereas SyncDroid only works with Windows PCs, Androidsoft Assistant is compatible with both Macs and Windows PCs.
To create a computer backup using Androidsoft Assistant, first install the program in your computer, and launch it. Next, connect your phone to the computer using a USB cable. Once the software recognizes your phone, tap Yes on your phone's screen to enable USB debugging. Wait a few minutes for the software to analyze the content currently on your device.
Once a screen listing items currently on your phone appears, select Contacts, and click Import/Export. Click Export All Contacts to Computer, and select a local directory to store the exported contacts. Choose a suitable file format for the exported contacts.
To back up iPhone contacts, go to Settings, and tap Import SIM Contacts. Connect the iPhone to a PC using a USB cable, launch iTunes, and click the iPhone icon on the left side of the iTunes window. Click Info, tick the checkbox next to Sync Address Book and Contacts, and click Sync. Wait a few minutes for the contacts to copy to your computer.