A Lot Of People Are Complaining That Half The Galaxy S4's Memory Is Used Up When You First Buy It
This applies to the 16 GB version, which has nearly 8 GB used up by the operating system, preinstalled apps from Samsung and its carrier partners, and the array of extra features Samsung added to Android.
In a statement to CNET, Samsung said users have the option to add more memory with a SD card, something its rivals the HTC One and iPhone can't do.
Here's that statement:
For the Galaxy S4 16 GB model, approximately 6.85 GB occupies the system part of internal memory, which is 1 GB bigger than that of the Galaxy S3, in order to provide a high resolution display and more powerful features to our consumers.
To offer the ultimate mobile experience to our users, Samsung provides a microSD slot on Galaxy S4 for extension of memory.
However, you aren't allowed to install apps on the SD card, so it's really only good for storing extra music, photos, videos, etc. That means it's still pretty easy to quickly fill up the 16 GB model of the Galaxy S4, especially if you download large apps like graphics-intense games. Samsung's 6.85 GB figure apparently doesn't take into account the extra apps carriers preinstall on the phone.
For comparison's sake, the iPhone's operating system uses up a little more than 1 GB of the phone's internal storage.