What is Unix?
Section 1: What Is UNIX?
UNIX is an operating system. The job of an operating
system is to orchestrate the various parts of the computer -- the
processor, the on-board memory, the disk drives, keyboards, video
monitors, etc. -- to perform useful tasks. The operating system is
the master controller of the computer, the glue that holds together
all the components of the system, including the administrators,
programmers, and users. When you want the computer to do something
for you, like start a program, copy a file, or display the contents of
a directory, it is the operating system that must perform those tasks
More than anything else, the operating system gives the computer
its recognizable characteristics. It would be difficult to
distinguish between two completely different computers, if they were
running the same operating system. Conversely, two identical
computers, running different operating systems, would appear
completely different to the user.
UNIX was created in the late 1960s, in an effort to provide a
multiuser, multitasking system for use by programmers. The philosophy
behind the design of UNIX was to provide simple, yet powerful
utilities that could be pieced together in a flexible manner to
perform a wide variety of tasks.
The UNIX operating system comprises three parts: The kernel, the
standard utility programs, and the system configuration files.
The kernel is the core of the UNIX operating system. Basically,
the kernel is a large program that is loaded into memory when the
machine is turned on, and it controls the allocation of hardware
resources from that point forward. The kernel knows what hardware
resources are available (like the processor(s), the on-board memory,
the disk drives, network interfaces, etc.), and it has the necessary
programs to talk to all the devices connected to it.
The standard utility programs
These programs include simple utilities like cp, which copies files,
and complex utilities, like the shell that allows you to issue
commands to the operating system.
The system configuration files
The system configuration files are read by the kernel, and some of
the standard utilities. The UNIX kernel and the utilities are
flexible programs, and certain aspects of their behavior can be
controlled by changing the standard configuration files. One example
of a system configuration file is the filesystem table "fstab" , which
tells the kernel where to find all the files on the disk drives.
Another example is the system log configuration file "syslog.conf",
which tells the kernel how to record the various kinds of events and
errors it may encounter.
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