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Unix - an Inroduction

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UNIX - An Inroduction
By: Adam Racer

What is an operating system? · Kernel - provides a well-defined interface between programs and the hardware. It is a resource manager where the resources include memory, CPU access, input/output ports, etc. · Shell - interacts with the user, accepting commands and starting user programs. · Utilities - include programs required to make the system useful, such as programs to copy files, or simple text editors. · Windowing system - a collection of programs that implement a graphical user interface. Although the traditional definition of an operating system includes just the kernel, it is now more commonly known as a collection of most or all of these components. How A Kernel Defines the Operating System How a kernel defines the interface between programs and the underlying hardware greatly affects the programs designed for that operating system. Some features that define the kernel are: · Single or Multi-Tasking · A single-tasking operating system allows only one program to run at a time. This program must complete before a second program may begin. · A multi-tasking operating system allows multiple programs to run on the same system. In order to do this, it must define a means of communicating between programs, protecting running programs from errors encountered in other programs, and for scheduling when programs will run. · Single or Multi-User · A single-user operating system has only one user at a time. This user is granted exclusive access to all system resources. · A multi-user operating system can have more than one user at the same time. Most multi-user operating systems are also multi-tasking. · Memory Management · This defines how memory is allocated to specific tasks, and how memory is protected from other processes. · Device Interface · Device interfaces define the nature of the peripherals which may be connected to a system, the ease with which new devices are added, the extent to which the full power of a...

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