Design and implementation of software vary depending on the complexity of the software. For instance, the design and creation of Microsoft Word took much more time than designing and developing Microsoft Notepad because the latter has much more basic functionality.

Software is usually developed in integrated development environments (IDE) like Eclipse, IntelliJ and Microsoft Visual Studio that can simplify the process and compile the software.^{[citation needed]} As noted in a different section, the software is usually created on top of existing software and the application programming interface (API) that the underlying software provides like GTK+, JavaBeans or Swing.^{[citation needed]} Libraries (APIs) can be categorized by their purpose. For instance, the Spring Framework is used for implementing enterprise applications, the Windows Forms library is used for designing graphical user interface (GUI) applications like Microsoft Word, and Windows Communication Foundation is used for designing web services.^{[citation needed]} When a program is designed, it relies upon the API. For instance, a Microsoft Windows desktop application might call API functions in the .NET Windows Forms library like Form1.Close() and Form1.Show() to close or open the application. Without these APIs, the programmer needs to write these functionalities entirely themselves. Companies like Oracle and Microsoft provide their own APIs so that many applications are written using the software libraries that usually have numerous APIs in them.^{[citation needed]}

Data structures such as hash tables, arrays, and binary trees, and algorithms such as quicksort, can be useful for creating software.

Computer software has special economic characteristics that make its design, creation, and distribution different from most other economic goods.^{[specify][22][23]}

A person who creates software is called a programmer, software engineer or software developer, terms that all have a similar meaning. More informal terms for programmer also exist such as "coder" and "hacker" – although the use of the latter word may cause confusion because it is more often used to mean someone who illegally breaks into computer systems.