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In computer programming, an entry point is where control enters a program or piece of code.
In most of today's popular computer systems, such as Microsoft Windows and Unix, a computer program usually only has a single entry point. In C, C++, D and Kotlin programs this is a function named
main; in Java it is a static method named
main, and in C# it is a static method named
One notable modern exception to the single-entry-point paradigm is Android. Unlike applications on most other operating systems, Android applications do not have a single entry point – there is no
main() function, for example. Instead of a single entry point, they have essential components (which include activities and services) which the system can instantiate and run as needed.
Historically, and in some contemporary legacy systems, such as VMS and OS/400, computer programs have a multitude of entry points, each corresponding to the different functionalities of the program. The usual way to denote entry points, as used system-wide in VMS and in PL/I and MACRO programs, is to append them at the end of the name of the executable image, delimited by a dollar sign ($), e.g.
directory.exe$make. The Apple 1 computer also used this to some degree. For example an alternative entry point in Apple 1 BASIC would keep the BASIC program[clarification needed] useful when the reset button was accidentally pushed.
- "Application Fundamentals". Android Development. linuxtopia.org. Retrieved 2014-02-19.
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