4. User-Defined Functions

Software is a detailed set of instructions that tell the computer what to do. There are numerous examples where we, as humans, follow a set of such instructions. As a simple example, many pieces of furniture from IKEA come with a set of high-level instructions in the form of pictures. When creating these instructions, the people at IKEA assume a certain level of basic knowledge of how to use tools, such as a wrench, a screwdriver, a hammer, and so on.