Aleph is a discontinued

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

kernel developed at the

University of Rochester The University of Rochester is a private university, private research university in Rochester, New York, United States. It was founded in 1850 and moved into its current campus, next to the Genesee River in 1930. With approximately 30,000 full ...

as part of their Rochester's Intelligent Gateway (RIG) project in 1975. Aleph was an early step on the road to the creation of the first practical

microkernel In computer science, a microkernel (often abbreviated as μ-kernel) is the near-minimum amount of software that can provide the mechanisms needed to implement an operating system (OS). These mechanisms include low-level address space management, ...

operating system,

Mach The Mach number (M or Ma), often only Mach, (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a Boundary (thermodynamic), boundary to the local speed of sound. It is named after the Austrian physi ...

. Aleph used

inter-process communication In computer science, interprocess communication (IPC) is the sharing of data between running Process (computing), processes in a computer system. Mechanisms for IPC may be provided by an operating system. Applications which use IPC are often cat ...

s to move data between programs and the kernel, so applications could transparently access resources on any machine on the local area network (which at the time was a 3-Mbit/s experimental

Xerox Xerox Holdings Corporation (, ) is an American corporation that sells print and electronic document, digital document products and services in more than 160 countries. Xerox was the pioneer of the photocopier market, beginning with the introduc ...

Ethernet Ethernet ( ) is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...

). The project eventually petered out after several years due to rapid changes in the computer hardware market, but the ideas led to the creation of Accent at

Carnegie Mellon University Carnegie Mellon University (CMU) is a private research university in Pittsburgh, Pennsylvania, United States. The institution was established in 1900 by Andrew Carnegie as the Carnegie Technical Schools. In 1912, it became the Carnegie Institu ...

, leading in turn to

. Applications written for the RIG system communicated via ''ports''. Ports were essentially message queues that were maintained by the Aleph kernel, identified by a ''machine'' unique (as opposed to globally unique) ID consisting of a process id, port id pair. Processes were automatically assigned a process number, or ''pid'', on startup, and could then ask the kernel to open ports. Processes could open several ports and then "read" them, automatically blocking and allowing other programs to run until data arrived. Processes could also "shadow" another, receiving a copy of every message sent to the one it was shadowing. Similarly, programs could "interpose" on another, receiving messages and essentially cutting the original message out of the conversation. RIG was implemented on a number of

Data General Eclipse The Data General Eclipse line of computers by Data General were 16-bit minicomputers released in early 1974 and sold until 1988. The Eclipse was based on many of the same concepts as the Data General Nova, but included support for virtual memo ...

minicomputer A minicomputer, or colloquially mini, is a type of general-purpose computer mostly developed from the mid-1960s, built significantly smaller and sold at a much lower price than mainframe computers . By 21st century-standards however, a mini is ...

s. The ports were implemented using memory buffers, limited to 2 kB in size. This produced significant overhead when copying large amounts of data. Another problem, realized only in retrospect, was that the use of global ID's allowed malicious software to "guess" at ports and thereby gain access to resources they should not have had. And since those IDs were based on the program ID, the port IDs changed if the program was restarted, making it difficult to write servers with clients that could rely on a specific port number for service.

References

* * *{{cite web , last1=Ball , first1=E. , display-authors=etal , title=RIG, Rochester's Intelligent Gateway: System Overview , url=https://urresearch.rochester.edu/fileDownloadForInstitutionalItem.action?itemFileId=31505&itemId=13614 , website=rochester.edu , access-date=March 31, 2023 Monolithic kernels University of Rochester