HELLO is a C program which says "Hello, world!".
If you're just trying to learn C, or learning how to use C on a different computer system, or in batch mode, it's helpful if you start with a very simple program with a tiny amount of output that should print immediately if things are working well.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
HELLO is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.
HELLO_MPI, a C program which prints out "Hello, world!" using the MPI parallel programming environment.
HELLO_OPENMP, a C program which prints out "Hello, world!" using the OpenMP parallel programming environment.
You can go up one level to the C source code page.