IntelliSense is Microsoft’s implementation of autocompletion, best known for its use in the Microsoft Visual Studio integrated development environment. In addition to completing the symbol names the programmer is typing, IntelliSense serves as documentation and disambiguation for variable names, functions and methods using reflection.
Similar to other autocompletion systems, IntelliSense is a convenient way to access descriptions of functions, particularly their parameter lists. It speeds up software development by reducing the amount of name memorization needed and keyboard input required. It also allows for less reference to external documentation as interactive documentation on many symbols (i.e. variables and functions) in the active scope appears dynamically in the form of tooltips while programming.
IntelliSense works by accessing an automatically generated in-memory database of classes, variable names and other constructs defined in or referenced by the application being edited. The “classic” implementation of IntelliSense works by detecting marker characters such as periods, or other separator characters depending on the language used. As the user types one of these marker characters immediately after the name of an entity having one or more accessible members (such as contained variables or functions), IntelliSense starts suggesting matches with a pop-up window. The user can either accept the suggestion by typing a statement completion character (Tab ⇆ or ↵ Enter or a language-specific marker such as the semicolon for C++) or continue typing the name. Eventually IntelliSense will determine exactly which variable or function the user desires, given enough information. The feature also allows the user to select from a number of overloaded functions in the case of languages that support object oriented programming. IntelliSense can also display a short description of a function in the pop-up window (this feature depends on the amount of documentation contained in the source code of the function).