C SDK

You can compile C SDK applications on any platform, even running it without an operating system. The C SDK is the basis for all other SDKs and the EMS. It will result in an application that uses the least amount of RAM, processing power, and disk space, frequently requiring less than 200 kilobytes. It is also the only SDK that is distributed as source code.

Java SDK

Java application development is typically more rapid than C application development and the Java SDK is useful if you are integrating with an application that has a Java-based API. To use it, you must have a platform with a supported Java Virtual Machine. A Java SDK application typically uses more RAM, processing power, and disk space, than a C SDK equivalent application.
Learn and Explore Further:
Learn and Explore Further:

.NET SDK

The Microsoft.NET SDK is typically used when you either need to integrate with the .net based application, or if your team typically works with Microsoft technologies and doesn’t know C or Java well. It may only be used on Windows based machines.

iOS SDK

The iPhone Operating System SDK integrates with Apple iOS based devices like the iPhone, iPad, and iPod Touch. It is typically used as a bridge where the iOS device collects data from some source, be it Bluetooth or Wi-Fi, processes it, and communicates with the ThingWorx Platform.

Android SDK

The Android SDK is its own standalone open source operating system, it has been used as the operating system on dedicated devices, and the SDK may be used to integrate with those devices. However, dedicated devices are more likely to run Linux or Windows than Android.