Compression : Introduction

When data is stored it occupies space on a storage device such as a hard disk or floppy disk. When it is transmitted over a communications line it takes time to transmit. Buying storage space or time on a communication line costs money. To reduce the cost of these operations computer users often attempt to reduce the size of the data they want to store without losing any of the data.

Data compression is the act of reducing the size of a file without losing any of the data it contains. Decompression (also known as uncompression or expansion) is the act of taking a compressed file and converting it back to its original size and format. Because compression alters the format of the data in a file a compressed file must be decompressed before it can be used.

How much a file can be compressed by will depend upon the method being used to compress the file and the data that is stored in the file.

GCSE ICT Companion 04 - (C) P Meakin 2004