Creating a User executable File in C on linux?

Your program is a c program so It needs compiling with something like gcc this will give you an executeable, but I get the impression you need to create a script file that has echo "hello world" in it, you then need to do a chmod u+x filename, where file name is the name of your file that contains the echo "hello world", you should then be able to run it. You may need to add #!/bin/bash to the top of your file to explicitly state your file is a bash script.