Programs To Access System Resources

c)    DISTRIBUTED: A distributed operating system manages a group of distinct computers and makes them to appear to be single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing. Distributed computations are carried out on more than one machine. When computers in a group work in cooperation, they form a distributed system.
d)    TEMPLATED: In operating, distributed and cloud computing context, template refers to creating a single virtual machine image as a guest operating system, then saving it as a tool for multiple running virtual machine (Gagne, 2012, p. 716). The technique is used both in virtualization and cloud computing management, and is common in large server warehouse.
e)    EMBEDDED: Embedded operating systems are designed to be used in embedded computer systems. They are to operate on small machine like PDAs with less autonomy. They are to operate with a limited number of resources. They are very compact and extremely efficient by design. Windows CE and MINIX 3 are some examples of embedded operating systems.
f)    REAL-TIME: A real-time operating system is an operating system that guarantees to process events or data within a short amount of time. A real-time operating system may be single or multi-tasking, but when multi-tasking, it uses specialized scheduling algorithms so that a deterministic nature of behavior is achieved. An event-driven system switches between tasks based on their priorities or external events while time-sharing operating systems switch tasks based on clock interrupts.
3.4    EVOLUTION OF UNIX SYSTEMS
UNIX was originally written in assembly language. Ken Thompson wrote B, mainly based on BCPL, based on his experience in the MULTICS project. B was replaced by C, and UNIX, rewritten in C, developed into a large, complex family of inter-related operating systems which have been influential in every modern operating system.
The Unix-like family is diverse group of operating systems, with several major sub-categories including system V, BSD, and Linux. The name “UNIX” is trademark of the open group which license it for use with any operating system that has been shown to conform to their definitions. “UNIX-LIKE” is commonly used to refer to the large set operating systems which resemble the original UNIX.
Unix-like systems run on a variety of computer architectures. They are used heavily for servers in business, as well as workstations in academic and engineering environments. Free UNIX variants, such as Linux and BSD, are popular in these areas.
Four operating system are certified by the open group (holder of the UNIX trademarks) as UNIX. HP’s hp-Ux and IBM’s AIX are both descendant of the original system V, UNIX and are designed to run only on their respective vendor’s hardware. In contrast, sun Microsystem’s Solaris operating system can run on multiple types of hardware, including X86 and spare servers, and PC’s. Apple’s operating system X, are replacement for Apple’s earlier (non-Unix) Mac OS, is a hybrid Kernel- based BSD variants derived from Nextstep, Mach, and FreeBSD.
UNIX interoperability was sought by establishing the POSIX standards. The POSIX standards can be applied to any OS, although it was originally created for various UNIX variants.
3.5    BSD AND ITS DESCENDANTS
The first server for the World Wide Web ran on NeXTSTEP, based on BSD. A subgroup of UNIX family is the Berkeley software distribution family, which include FreeBSD, NetBSD and OpenBSD. These operating system are most commonly found on web servers, although they can also function as a personal computer OS. Internet owes much of its existence to BSD, as many of the protocols now commonly used by computers to connects, send and receive data over a network were widely implemented and refined in BSD. The World Wide Web was also demonstrated on a numbers of computers running an OS based on BSD called NeXTSTEP. BSD has its root in UNIX. In 1974, University of California, Berkeley installed its first UNIX system. Over time, students and staff in the computer science department there began adding new program to make things easier, such as text editors. When Berkeley received new VAX computers in 1978 with UNIX installed, the school’s undergraduates modified UNIX even more in other to take advantage of computer’s hardware possibilities. The defense advanced research project agency in the US department of Defense took interest, and decided to fund the project. Many schools, corporations, and government organization took notice and started to use Berkeley’s version of UNIX instead of official one distributed by AT & T.
Steve Jobs, upon leaving Apple Inc. in 1985, found NeXT Inc., in company that manufactured high-end computers running on a variation of BSD called NeXT STEP. One of this computers was used by Tim Berners-Lee as the first web server to create the World Wide Web.
Developer like Keith Bostic encouraged the project to replace many non- free code that originated with Bell labs. Once this was done however, AT & T sued. Eventually, after two years of legal disputes, the BSD project came out ahead and spawned a number of free derivatives, such as FreeBSD and NetBSD.
Android a popular mobile operating system using a modified version of Linux Kernel, the Linux Kernel originated in 1991 as a side project of Linus Torvalds, while a university student in Finland. He posted information about his project on a news group for computer students and programmers received support and assistant for the volunteers who succeeded in creating a complete and functional Kernel.
Linux is Unix-like, but was developed without any UNIX code, unlike BSD and its variants. Because of its open license model, the Linux Kernel code is available for study and modification which resulted in its use on a wide range of computing machinery from supper computers to smart- watches.
Although, estimate suggest that Linux is used on only 1.82 percent of all personal computers, it has been widely adopted for use in servers and embedded system such as cell phones. Linux as superseded UNIX on many platforms and is used on ten most supercomputer in the world. The Linux Kernel is used in some popular distributions such as Red Hat, Debian, Ubuntu, Linux mint and Google’s android.
Chromium is an OS based on the Linus Kernel and designed by Google. Since Chromium OS targets computer users who spends most of their time on the internet, it is mainly a web browser with limited ability to run local application, though it has a built-in file manager and media player. Instead, it relies on internet application (or web apps) used in the web browser to accomplish task such as word processing. Chromium OS differs from Chrome OS in that Chromium is open-source and used primarily by developer whereas Chrome OS shipped out in chrome Books.