How Java Works

A Little Terminology

Keep in mind that I am assuming that you know nothing about programming. Here are several vocabulary terms that will make things understandable:

  • Computer program - A computer program is a set of instructions that tell a computer exactly what to do. The instructions might tell the computer to add up a set of numbers, or compare two numbers and make a decision based on the result, or whatever. But a computer program is simply a set of instructions for the computer, like a recipe is a set of instructions for a cook or musical notes are a set of instructions for a musician. The computer follows your instructions exactly and in the process does something useful -- like balancing a checkbook or displaying a game on the screen or implementing a word processor.
  • Programming language - In order for a computer to recognize the instructions you give it, those instructions need to be written in a language the computer understands -- a programming language. There are many computer programming languages -- Fortran, Cobol, Basic, Pascal, C, C++, Java, Perl -- just like there are many spoken languages. They all express approximately the same concepts in different ways.
  • Compiler - A compiler translates a computer program written in a human-readable computer language (like Java) into a form that a computer can execute. You have probably seen EXE files on your computer. These EXE files are the output of compilers. They contain executables -- machine-readable programs translated from human-readable programs.

In order for you to start writing computer programs in a programming language called Java, you need a compiler for the Java language. The next section guides you through the process of downloading and installing a compiler. Once you have a compiler, we can get started. This process is going to take several hours, much of that time being download time for several large files. You are also going to need about 40 megabytes of free disk space (make sure you have the space available before you get started).