A hash function organizes data by manipulating it with a mathematical algorithm to produce a unique result. Numbers are often used to represent locations in a computer database, either arbitrarily or through the use of a hash function. Hash functions can also be used for error checking and breaking down repetitive data.
A hash function is a method of checking computer errors and organizing data. A large amount of data is manipulated with a mathematical algorithm until there is little left. This number is used as part of the catalog that allows a computer to find that specific piece of information later. A good hash function should give a result small enough to be easy to use, yet provide a unique result for each data set. A hash function also provides minimal error checking, since bad and good data should produce different results when hashed.
In a computer database, it is usually easier to save locations with numbers than with letters. Digits have a much greater number of methods for organizing and sorting than letters. As a result, numbers are often assigned to locations containing varying information within a computer’s database. These numbers can be arbitrary or representative of the information.
Arbitrary numbers are assigned simply based on their location in computer memory or the order in which the data was saved. Saving information this way is common in smaller databases or places where the data doesn’t change very often. When used in other areas, reindexing the database starts taking longer and longer until it is no longer efficient.
Representative information is where the hash function comes into play. Information, regardless of what it contains, is translated into numbers. These numbers are put into a mathematical construct that returns a small number, usually an integer. If the hash function works correctly, every location in that part of the database will have its own unique result. If two or more locations have the same result, programs may display incorrect information based on the duplicate hash.
You can use a hash function for other things as well. Large amounts of highly repetitive data can be broken down into smaller values. This is especially useful when searching for repeating sequences in large datasets. For example, deoxyribonucleic acid (DNA) is made up of a very small number of different components. When you decompose these components using hash values, the places where two strands of DNA are the same and different become very clear, just by comparing two small columns of numbers.
The last area where hash functions are useful is error checking. When information is initially encrypted, the value is recorded as part of the location index. If that information is needed at a later time, the information is retrieved along with that value. If the program reprocesses the information and the result is different, then a corruption has occurred at some point. This corruption is usually with the data, as a hash corruption would have prevented the data from being recovered in the first place.
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