What is Unix?

We have more than thousand of definitions available online but this is one is easy to know and understand.

Unix is multi tasking, multi-user operating system developed by AT&T (Bell Lab) in late 1969. Unix System consist a core kernel which does input output operations and allocate resources to carry out  user defined and system defined tasks.

Unix Filesystem is hierarchal which allows both absolute and relative path naming of file ,thus flexible.

Unix can be simply defines as multiuser,multiprocess and multithreaded.Example: A shell can be access ed by number of users at a time and in the same shell we can run different applications to respective different number of users.

Unix has Parent-Child system for the process.Process can be denoted by process ID (PID). Killing the parent process means all child process in turn dead ,as we can have this child process system so we can define which process to be kill and to save other running process.