UNIX Part 1: User Fundamentals -Unix Standards

Unix is based on the standards set by a number of organizations. A Unix standard is an agreed system by which all concerned parties conduct their computing and that covers all areas of the Unix operating system. The Unix user should be familiar with the major standards that are in existence.
The Portable Operating Interface (POSIX) standard measures whether a system is portable or not. For example, a program has portability if you can take a program from a System V Unix system and easily rework it to run on a Berkeley Software Distribution (BSD) system.
The Institute of Electrical and Electronic Engineers (IEEE) has created a series of standards committees for the POSIX standards. The POSIX.1 committee standardizes the C library interface used to write programs for Unix. The POSIX.2 committee standardizes the commands available for the general user.
The X/Open series of standards was founded by the X/Open consortium of computer vendors, software suppliers, and customers in Europe. X/Open brings together various Unix-related standards including the current attempt at a Common Open System Environment (COSE) specification. X/Open publishes a series of specifications called the X/Open Portability Guide (XPG). This guide consists of publicly available reference documents that define the steps to be taken by application developers when coding and compiling programs.
The OSF standard was developed by the Open Software Foundation (OSF). This was a cooperative venture by several Unix vendors including Digital, Hewlett Packard, IBM, and others. The OSF is supported by leading computer suppliers, many customers, and government agencies.
The United States Government has specified a series of standards based on XPG and POSIX.
There are several different ways to access a Unix machine. The first way is through the use of a workstation or a personal computer (PC).
You can also use a dumb terminal to connect to a Unix machine. A dumb terminal consists of a monitor, or terminal, and a keyboard. Dumb terminals are suited to many applications where graphics are not required, such as database entry. They are also inexpensive and effective.
An X terminal consists of a monitor, a keyboard, and a mouse. The difference between an X terminal and a dumb terminal is that an X terminal provides the user with a graphical environment. You use the mouse to manipulate windows. The graphical interface used on X terminals is the X window System.
You can also use Unix over a network connection. Workstations, PCs, dump terminals, and X terminals can initiate either of the two types of network connections displayed on the screen (LAN Connection and Telnet Connection).
A standard feature of Unix that is common to all versions it the kernel. It is important to understand how the kernel works. The kernel is the system control process of the Unix operating system. It is the layer of software that interacts with the hardware.
The kernel executes programs by issuing instructions to the Central Processing Unit (CPU). It controls the allocation of computer hardware and memory and controls the peripheral devices connected to the computer. It also manages all computer resources.