Before computers, fingerprints were stored on cards and categorized based on the category of pattern made by the ridges. In 1924, the Identification Division of the FBI was established by congress and by 1946, the FBI had processed over 100 million fingerprint cards. By 1971, the FBI stored over 200 million fingerprint cards.
To make a match, a person had to look at each card of that type and manually verify the match. Obviously, it was a slow and tedious process. Today, fingerprints are converted into a mathematical construct called a template. Specific features of the fingerprint called minutiae points are identified and a vector is created from the point to the fingerprint core. A fingerprint template is a mathematical representation of the minutiae points and their relationship to each other. Templates are much smaller than images. A fingerprint template can be as small as 600 bytes and a fingerprint image is around 500,000 bytes. The smaller size means they are faster to match and less expensive to store.
Even though the computer finds the likely matches in the database, a human being always verifies the match using the images.