The history of library catalogs dates back to the invention of writing and the keeping of written records. In the ancient world, clay tablets and scrolls were used to record the contents of libraries, and these records were kept by librarians. The invention of the printing press in the 15th century led to the creation of printed catalogs, which allowed libraries to catalog their collections more efficiently. The 19th century saw the advent of the card catalog, which used index cards to record the information about library materials. This system was widely used throughout the 20th century, but has since been mostly replaced by computerized catalogs. Today, most libraries use online catalogs, which allow users to search and access library materials from anywhere with an internet connection.