Unix architecture

A Unix architecture is a computer operating system system architecture that embodies the Unix philosophy. It may adhere to standards such as the Single UNIX Specification (SUS) or similar POSIX IEEE standard. No single published standard describes all Unix architecture computer operating systems - this is in part a legacy of the Unix wars.
Description.
There are many systems which are Unix-like in their architecture. Notable among these are the Linux distributions. The distinctions between Unix and Unix-like systems have been the subject of heated legal battles, and the holders of the UNIX brand, The Open Group, object to "Unix-like" and similar terms.
For distinctions between SUS branded UNIX architectures and other similar architectures, see Unix-like.
Kernel.
A Unix kernel — the core or key components of the operating system — consists of many kernel subsystems like process management, scheduling, file management, device management, network management, memory management, and dealing with interrupts from hardware devices. 
Each of the subsystems has some features:
The kernel provides these and other basic services: interrupt and trap handling, separation between user and system space, system calls, scheduling, timer and clock handling, file descriptor management.
Features.
Some key features of the Unix architecture concept are:
The UNIX operating system supports the following features and capabilities:
Criticism.
"The Unix-Haters Handbook" covers some of these design features as failures from the user point of view. However, although some information is quite dated and cannot be applied to modern Unixes or Unix-like operating systems such as Linux, Eric S. Raymond discovered that several issues are still prevailing, while others were resolved. Raymond concludes that not all concepts behind Unix can be deemed as non-functional even though the book's intention may have been to portray Unix as inferior without encouraging discussions with developers to actually fix the issues.