What is a checksum? Imagine the situation: you've downloaded the file, and then found out that it is defective (for example, a program that you are trying to open it, an error message, but the other files of the same format opens up "a great success").How to check whether he was originally defective, or whether there have been any problems with downloading?That's what checksum file.

checksum file ( hash ) - it is a certain value, which is calculated on a set of data using an algorithm.It helps to check the integrity of data during storage and transmission. If two identical files, the checksum, it means that these files are identical in content , even if, for some reason, have different names.

There are different hashing algorithms to create checksums.For example, the program-archiver using the so-called cyclic redundancy code ( CRC ).It allows you to make sure that decompress the file from the archive took place without problems, a resulting file is identical to the original.The program uses an algorithm BitTorrent SHA-1 , to verify the integrity of downloaded data.To check the integrity of downloaded files and find duplicate files are commonly used algorithm MD5 .

Let's say you decide to download the operating system distribution.If the injection occurs a failure, the operating system can be established "crooked" or not install at all.A checksum will help determine whether the file you downloaded with the original.For these purposes, a checksum is usually indicated on the website that provides files for download.You just need to learn checksum file you downloaded and compare two values.If the checksums match, the files are identical.

checksum is determined by means of special programs. One of the most popular programs for checksum files - HashTab .This program is free, it is easy to download and install.It does not even need to run - it integrates into the context menu of the operating system.Incidentally, among the supported languages ​​are Russian.There are versions of the program for Windows (XP, Vista, Seven) and Mac OS X.

So you have downloaded and installed the program, what's next?Open Explorer or any other file manager folder with the file checksum you want to check.Click on the file, right-click, select the context menu, click Properties.In the window that opens, click the hash of the files and wait: program will take some time to calculate checksums .

HashTab defines the value of the hash algorithms Adler32, CRC32, MD2, MD4, MD5, RIPEMD-128, RIPEMD-256, RIPEMD-320, SHA-1, SHA-256, SHA-384, SHA-512, Tiger and Whirlpool.By default, the checksum is calculated for the three most popular algorithms, CRC32, MD5 and SHA-1.If desired, you can select the other algorithms by clicking on the link under the Settings window with the value of the hash.The program also allows you to HashTab compare the hash value of the two files on the computer .

Another free program to check the hash file - MX MD5 Calculator .It checksum is calculated using the algorithm MD5.In principle, the "domestic" purposes variety of algorithms you to anything, MD5 should be quite enough.The program works on the operating system Windows (XP, Vista, Seven).However, unlike HashTab, it does not work on 64-bit versions.Unfortunately, the Russian language there is not, but even in the English version of the deal is not so difficult.

download and install the program, run it.Click the Browse button next to the line 1 File and select the file checksum which you are interested.After selecting the file, click Calculate (it is right under the button Browse).Counting hash sum takes some time.It depends on the configuration and utilization of your computer.To count went faster, it is advisable to close all other applications.After the end of counting in a row will be sought MD5 checksum. To compare two hash files, you can select a file in rows File 1 and File 2 .

What is a checksum?