An application program is run in a process supported by an operating system in a computer system. The application program is executed in a virtual machine, and the virtual machine is within the process. Loading a library for the application program includes determining whether this is the first library load instruction in the application program. If it is the first library load instruction, then the library is loaded in a first memory area, and a handle and link map to the first memory area is defined for the library. If the library load instruction is a second or subsequent library load instruction, the further library is loaded in a further memory area, also associated with the link map identifier, and a second handle to the further library is defined and stored.