In general, an access code is a string of characters that allows an authenticated identity to gain access to a particular content or system. Although similar in purpose to passwords, access codes need not have a one-to-one correspondence with each user. Multiple users may use the same access code.
Office personnel and programmers often use access codes to restrict content and increase the security for the company. For students, however, aside from access to school systems, access codes most often refer to a passkey that comes with new textbooks and modules. These provide students access to additional online enrichment materials, worksheets or even an electronic copy of the book.