Editing OSF/1 (section)

== Background ==
In 1988, during the so-called "[[Unix wars]]", [[Digital Equipment Corporation]] (DEC) joined with [[IBM]], [[Hewlett-Packard]], and others to form the [[Open Software Foundation]] (OSF) to develop a version of Unix named OSF/1. The aim was to compete with [[UNIX System V#SVR4|System V Release 4]] from [[AT&T Corporation]] and [[Sun Microsystems]], and it has been argued that a primary goal was for the operating system to be free of AT&T [[intellectual property]].<ref>{{cite book |author=Salus, Peter H. |title=A Quarter Century of UNIX |publisher=Addison-Wesley Pub. Co |location=Reading, Mass |year=1994 |page=217 |isbn=0-201-54777-5}}</ref> The fact that OSF/1 is one of the first operating systems to have used the Mach kernel is cited as support of this assertion.{{citation needed | date=January 2024 | reason=A fact supported by a citation, but where is the citation?!}} Digital also strongly promoted OSF/1 for [[real-time computing|real-time]] applications, and with traditional UNIX implementations at the time providing poor real-time support at best, the real-time and [[thread (computing)|multi-threading]] support can be interpreted as having been heavily dependent on the Mach kernel. At the time of its introduction, OSF/1 became the third major flavor of UNIX together with [[UNIX System V|System V]] and BSD.

OSF/1 at its inception combined Mach 2.5 with a large part of the [[Berkeley Software Distribution|BSD]] kernel (based on the 4.3-Reno release) to implement the UNIX [[API]],<ref name="usenix1993winter_zajcew">{{ cite journal | url=https://archive.org/details/1993-proceedings-winter-san-diego/page/449/mode/1up | title=An OSF/1 UNIX for Massively Parallel Multicomputers | journal=Proceedings of the Winter 1993 USENIX Conference | publisher=USENIX Association | date=1993 | access-date=23 January 2024 | first1=Roman | last1=Zajcew | first2=Paul | last2=Roy | first3=David | last3=Black | first4=Chris | last4=Peak | first5=Paulo | last5=Guedes | first6=Bradford | last6=Kemp | first7=John | last7=LoVerso | first8=Michael | last8=Leibensperger | first9=Michael | last9=Barnett | first10=Faramarz | last10=Rabii | first11=Durriya | last11=Netterwala | pages=449–468 }}</ref>{{rp | pages=451 | quote=OSF/1 is based on the Mach 2.5 operating system from Carnegie Mellon University. Both are integrated or monolithic kernel systems that implement the majority of system functionality in the operating system kernel (but not all, for example OSF/1’s program loader runs in user space). Their kernels contain the core Mach technology and additional Unix functionality. OSF/1 has significantly upgraded the 4.3BSD portion of Mach 2.5 to implement advanced features and obtain compliance with standards.}} with this monolithic kernel arrangement continuing through the OSF/1 1.2 release, although the adoption of a microkernel had already been foreseen.<ref name="osf1993_design">{{ cite book | url=https://archive.org/details/bitsavers_osfDesignostemRelease1.21990_25637674/page/n36/mode/1up | title=Design of the OSF/1 Operating System Release 1.2 | publisher=P T R Prentice-Hall Inc. | date=1993 | access-date=24 January 2024 | pages=1–12 | quote=Currently, OSF/1 integrates the core kernel services with the system services into one monolithic kernel. In future versions, the kernel will contain only the primitive objects and operations provided by a microkernel; most of what is now contained in the system services will be moved into its own, separate address space. }}</ref> OSF/1 1.3 introduced such a microkernel in the form of Mach 3.0, hosting Unix system services separately in user space to provide the existing OSF/1 functionality.<ref name="byte199401_kernels">{{ cite magazine | url=https://archive.org/details/eu_BYTE-1994-01_OCR/page/n153/mode/1up | title=Small Kernels Hit It Big | magazine=Byte | last1=Varhol | first1=Peter D. | date=January 1994 | access-date=24 January 2024 | pages=119–120, 122, 124, 126, 128 }}</ref>