The phrase "Hello, World!" has its roots in the early days of computer programming. Its first known appearance was in a 1974 Bell Labs memorandum by Brian Kernighan, titled A Tutorial Introduction to the Language C. Kernighan used a simple "Hello, World!" program to demonstrate how the C programming language works.
The phrase gained widespread popularity through the 1978 book The C Programming Language by Brian Kernighan and Dennis Ritchie (often called "K&R"). In it, the authors presented a minimal C program that printed "Hello, World!" to the console as the very first example — making it the canonical way to introduce a new programming language to beginners.
Before its use in programming, "hello" itself became a common greeting in the late 1800s, largely popularized by Thomas Edison, who suggested it as the standard way to answer the telephone. The pairing of "hello" with "world" in the K&R tradition simply reflected the idea of a program announcing itself to the outside world.
Today, writing a "Hello, World!" program is a universal tradition in software development. It serves as the simplest possible test to verify that a language, environment, or system is set up and working correctly, and it remains the first program most programmers ever write.