(1) (Hardware Abstraction Layer) An interface between the hardware and the software. An operating system is essentially a hardware abstraction layer; however, a HAL implies an additional layer between the OS and the hardware. It is used to enable the operating system to be ported to new hardware platforms by writing a new abstraction layer. In practice, parts of the kernel may always have to be optimized in order to support new hardware as efficiently as possible.

(2) (Heuristic/ALgorithmic) The name of the computer in Stanley Kubrick's famous film "2001," which takes over command of the spaceship. Each of the letters in H-A-L precede the letters I-B-M. In 1968, when the movie was released, IBM controlled almost every aspect of the computer business; however, the IBM name connection was supposedly a coincidence.