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 for you.

 

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

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.