SDK: What Exactly is a Software Development Kit?

Software developers face all sorts of challenges in their daily work. Besides pure programming, concepts and prototypes must be designed for new applications, development steps planned and organised, and interim results analysed. And wherever there are errors or weak points, these also need to be resolved. The trend of increasing complexity in software only makes these tasks more difficult. That’s why modern development work can scarcely be imagined without aids like frameworks – ready-made code structures.

Another essential tool is software development kits (SDKs), which play a central role in typical work with programming languages as well as the platform-specific development and provision of software.

A software development kit, or SDK for short, is a package of tools and information that helps developers to create programs in a certain programming language, for a certain platform or application – or even enables them to do so in the first place. Compiling and releasing an SDK is up to the original developer of the respective language or hardware/software, who in turn has a natural interest in helping third-party software for their product or programming language to enter the market. In most cases, software development kits are therefore available to use for free, although the manufacturer can define certain rules and licenses.

The composition of an SDK varies from manufacturer to manufacturer. The scope of a kit also depends on whether it is intended for a language, operating system or hardware. Standard components contained in almost all software development kits include the API (or APIs) for connecting new software projects at the level of the source text. These programming interfaces are typically provided with extensive documentation that covers explanations on how to use the API as well as other useful information. This way interested developers can quickly get an overview of whether and how their planned project can be implemented.

A good software development kit should also be supplied with all technical core components such as editors, libraries, run-time and development environments, compilers and debuggers (as well as other test/analysis tools, if available) if they are necessary for development or significantly simplify the development process. Likewise, special drivers and network protocols that are required should also be included. In some cases, manufacturers also add examples or small test projects to their SDKs in order to make it as easy as possible for developers to get started.

Here’s a summary of the components that may be found in software development kits:

• API(s)
• Documentation
• Editors
• Libraries
• Run-time and development environments
• Compilers
• Debuggers
• Drivers
• Network protocols
• Examples/test projects

As mentioned above, most SDKs are available for free. This is primarily because new software for a system or device represents one of the easiest ways for any manufacturer to increase added value for users. This is especially evident with smartphones and tables, which would only garner a fraction of the interest they have without third-party apps. However, certain rules may be tied to the download and use of software development kits.

For example, a manufacturer may only grant access to an SDK if a user agrees not to pass on confidential information. Non-disclosure agreements are especially common for software with secret algorithms and products at an alpha or beta stage. To ensure that the created software is not released under another incompatible license, a software development kit can also be subject to a license. Both proprietary and free licenses are possible here. For this reason, developers should consider the underlying models before they start their work – as shown by the following examples:

• If an SDK has a proprietary license, it is unsuitable for developing open-source software.
• In turn, software development kits with a GNU General Public License (GPL) are not suitable for the development of proprietary applications.
• A software development kit provided under the free GNU Lesser General Public License (LGPL) can also be used for projects with proprietary code elements. However, these kinds of projects must always be created in a way that permits end users to view and modify the open-source component of the software at any time.