There's a huge amount of apps for smartphones. Some are so popular that they are made for both Android and iOS operating systems. But, some are exclusive to only one operating system. 

Here's some apps that are either exclusive to Apple's iOS or to Android.

iTunes U (iOS)

iTunes U allows students access to courses from some of the best universities around the world. What a great way to learn a subject, right on your smartphone. iOS devices already have this app pre-installed.

Cover Lock Screen (Android)

Recently acquired by Twitter, Cover offers Android users convenience. The app learns the users' app usage and when and where the user typically uses those apps. From there, when the user locks their phone, depending on what time it is or where they are located, shortcuts appear on the lock screen with icons to those apps.

Garage Band (iOS)

Whether you're a pro or a wannabe rocker, Garage Band is a powerful and versatile music-recording app. It's the best app of its kind available on a mobile device.

Friday: Automated Journal (Android)

This app runs in the background while you are doing your normal activities on your Android. It tracks what songs you listen to, who you call or text, where you check in and much more. It allows you to go back in time and serves as a search engine in your life. Download the app here.

Camera+ (iOS)

The app is so powerful, you may never use the built-in iOS camera again. Aside from the filters that are offered, there is a feature called "clarity" that automatically fixes your photos and vastly improves the quality of them. Download the app here.

AppLock (Android)

Has your friend ever gotten a hold of your phone and posted an embarassing status on your Facebook wall? Ever regreat sending a late night text to your ex? With AppLock you'll be able to lock access to certain apps based on settings you choose. A pin will have to be entered if you choose that setting. But, if you tell AppLock not to run during certain times of the day, it will remain locked. Download the app here.

All of these apps are free, so head to your app store and download them. Leave a comment on what you think the best iOS app is or leave a comment on your favorite Android app.