1. The canonical minimal test message in the C/Unix universe.
2. Any of the minimal programs that emit this message (a
representative sample in various languages can be found at http://www.latech.edu/~acm/helloworld/).
Traditionally, the first program a C coder is supposed to write in a new
environment is one that just prints hello, world
to standard
output (and indeed it is the first example program in K&R). Environments that generate
an unreasonably large executable for this trivial test or which require a
hairy compiler-linker invocation to generate it are
considered to lose (see X).
3. Greeting uttered by a hacker making an entrance or requesting
information from anyone present. Hello, world! Is the LAN back up
yet?