Libraries could also be accessed 'by title' and 'by function'. In 'by title' the client specified the file name of the library. 'By function' was an indirect method where a client would just specify the function name of the library, for example 'system_support' and the actual location of the library is found in a table previously set up by an operator with 'SL' (system library) commands, for example 'SL system_support = *system/library/support'. MCP's fault tolerant attitude also works here – if a client tries accessing a library that is not present, the client is put in the 'waiting' tasks and the library could be made present, or the request redirected.