File Names

The sole function of a computer is to process information. How the information is to be processed is defined by the SOFTWARE (the computer program) and what information is processed is determined by the FILES (the data) on which the program operates. So, a very general plan of the way a computer works is:-

Input file(s) $\Rightarrow$ Software $\Rightarrow$ Output files(s)

Files are usually stored on DISK which comes in a wide range of formats e.g. floppy, hard and optical. They can also be stored on TAPE which can be divided into two broad groups: reels (which are now obsolete) and cassettes. Particle Physics and Central Physics no longer use tape systems.

Each file is given a name, and when on disk this name must be unique. It is used to identify the file. It is typically of the form:-

filename.extension e.g. myfile.dat

i.e. it consists of two names separated by a full stop. These two names perform different functions:-

Filename

is an arbitrary name chosen by the user to remind himself or herself with what task the file is associated.

Extension

is generally determined by the program that created the file and indicates the type of information.

This scheme allows files to be grouped together into ``families''. For example, suppose we have an accounts program that reads an accounts file and produces a summary we might set up 3 files:-

accounts.exe 		 The accounts program.


accounts.in 		 The input accounts file.


accounts.out 		 The output summary file.

So the filename accounts reminds us what the task is while the extensions .exe, .in and .out tell us what information each file contains.