These library files have their own format and so can only be used with Blitz. Each library must also have its own unique ID number (which can cause problems when you want to use commands from a library whose number clashes with another, or if someone has saved their source in tokenised format and have a different set of libraries from you).

As well as the 3^rd party libraries which have been specifically written for Blitz, it is also possible to use standard OS shared libraries by converting them and using them as 3^rd party libraries.

To install any new libraries, you must put the library file into the appropriate subdirectory of the Blitzlibs: assign and then run the makedeflibs program to recompile the deflibs file. OS shared libraries are put into Blitzlibs:amigalibs/ directory and are usually named <library_name>.<type><number>. The type is what the OS library is, for example library, device, resource, gadget, etc. The number is used if a library has too many commands to fit into one Blitz library, e.g. dos.library1 and dos.library2. Other 3^rd party libraries will usually go into the Blitzlibs:userlibs/ or Blitzlibs:otherlibs/ directories. More details about installing OS libraries will be given later in this section.