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A "Hello, World!" program generally is a computer program that outputs or displays the message "Hello, World!". Such a program is very simple in most programming languages, and is often used to illustrate the basic syntax of a programming language. It is often the first program written by people learning to code. It can also be used as a sanity test to make sure that a computer language is correctly installed, and that the operator understands how to use it.
Source: Wikipedia