File comparison is a method utilized to compare two files and evaluate the differences between them. The output of the comparison is usually shown to the user and can be used to complete tasks in networks, file systems, and revision control. Examples of software that can complete this task are the diff and the cmp. This method of comparing files is essential when the programmer is deliberating which of the files is superior. The files may differ with regards to the volume of storage space required, the time it takes for the files to be executed, their resistance to virus attacks and tampering, and a variety of other things that the programmer may want to consider.

Many tools are already available for the comparison of files. Some tools are GUI-based and will display the differences side by side in a window. Others may even highlight the difference to give more emphasis while others, like the diff, are command line based. Furthermore, some tools support only text files, whereas others have the capacity to evaluate binary files.

Most file comparing software find the longest common subsequence, while others find the longest increasing subsequence between two files. The LCS or the longest common subsequence is basically finding the longest subsequence that is common to all the sequences in a set of sequences. On the other hand, the LIS or the longest increasing subsequence is mainly searching through the entire sequence, to find the points where the values decrease and determining the longest gap between the two points.

Before the advent of file comparison software, there were already machines that compare magnetic tapes or punch cards. For instance, one machine was able to determine whether a set of punch cards were indeed corresponding. Nowadays, there are various types of file comparison software available. They are developed by diverse companies; some of which are established in this business, while others are from start-up companies. Most of these tools are proprietary, meaning they belong to the company or the person who created it. On the other hand, some of it is being licensed to other sectors or people.

File comparison software from different companies naturally have a number of diverse features. One can compare text and spreadsheets of a document and navigate simply through the indicated differences. Another type of comparing software might have the same features but can do such comparison a lot faster, and might have several add-ons, such as 3-way comparison, highlighting, patch creation, and version control browsing. So, it is advisable to examine the features before purchasing to decide which comparing software is suitable for your needs.

Having file comparison software is convenient, especially when you are considering which files you want to keep in your computer. Just think how laborious it would be to scrutinize through two versions of the same file, just to determine which has content that you prefer. It is like going through every word of both files just to attain your goal. With comparing software, this task can be done in a flash.