In about 800 CE the first library catalog was developed for the House of Wisdom in what is now Iraq. Since that time, and especially with the ease of publishing books that later came, most libraries have had to find ways of shelving books, and giving people who wanted to check them out a way of searching for them. For years, some form of card catalog system was used so that people could search, typically by author or title. Today, card catalogs are usually replaced by computer terminals where people can search, and these searches may not be limited to what’s in a library; instead many can use an online card catalog to widen access to material unavailable locally.
A number of types of online card catalog may be available to people, and what is available can depend on the library involved. Many public libraries that serve communities have searchable sites that can be accessed from home, if people have a library card that is used as a code. Libraries that have multiple branches might allow people to search all branches at once, and the location of any books found may be noted in catalog search results. Sometimes if people are looking for a specific book, they have to search each online card catalog separately per branch.
Since searching may sometimes be done from home, through a library’s website, there may be more functionality. Depending on the online card catalog, people might be able to order books, through interlibrary loan, if they’re not available at a local library. The number of libraries that might participate in any interlibrary loan is highly variable. Some libraries will only trade books with other branches.
Other libraries, especially university libraries, may have a much a wider net. Either at school or from home, students could use the online card catalog to borrow books from college libraries all over the country. This can significantly alter the degree to which students are able to thoroughly research subjects. Schools with poor libraries may be able to supplement students’ needs by offering participation in interlibrary loan. Though it can take a few weeks to get a book that is needed, this can be a great way for students to find what they need. Some library lending programs also exist for periodicals, though there may be a copying charge associated with this.
One thing that is common of most online card catalog programs is that people must go through or be members of a library in order to participate. It is usually not possible to borrow a book from “anywhere.” When these programs are in place, the book required is sent to the library of which a person is a member or participant, and it would be returned to that same library. Different rules may apply on length of checkout and very steep fines could occur if the book is not returned in perfect shape.