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OPERATING SYSTEM
An operating system is a program which acts as an interface between user and computer hardware
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OBJECTIVES OF OPERATING SYSTEM :
An operating system has two main objectives these are as follows :
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CONVENIENCE : an operating system makes a computer more convenient to use
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Operating system iS also known as resource manager
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So they are called as
resource allocator
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HOW OS TAKES CONTROL :
When we switch on computer certain logical steps takes place after this computer loads OS and passes the
control to it
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Following are the steps by which control is taken –
Computer checks itself to see if the basic devices are connected with processor
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-> BIOS ROUTINE : The basic input output system (BIOS) is a part of computer ‘s read only memory
performs checking the memory of the computer
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The area of
the disk where these files are located is called boot sector
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->CONFIGURING FILES LOADING : Once these files are loaded few more configuration files are also
required which contain what to do upon the start up of computer
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PROCESSOR MANAGEMENT FUNCTION : It allocates the processor to execute a chosen
process
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FILE MANAGEMENT FUNCTION : It keeps track of all the information about files that how they
are opened or closed
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There was a bare machine
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programming on bare machine
results ;ow productivity
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BATCH PROCESSING : Batch is defined as a group of jobs with similar needs
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computer executes each batch considering them as a single
process is called batch processing
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Hence SPOOLING stands for simultaneous peripheral operations
online
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Spooling is
the multiprogramming application
MULTIPROGRAMMING : multiprogramming increases CPU utilisation by organising jobs in
such a manner that CPU has always one job to execute
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In this at the same time more than one program can be executed due to high speed of
CPU
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In such system there are more than one user interacting the system at the
same time
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NETWORK : An operating system which includes software to communicate with other computer
through a network is called network OS
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CLIENT SERVER : A computer system in which server program is installed to provide various
services for their client is called server
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MULTI PROCESSOR : A multiprocessor system consists of a set of processors tat share a set of
physical memory blocks over an interconnection network
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DISTRIBUTED : Distributed OS are a OS for a network of autonomous computers connected by
a communication network through a message passing mechanism
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PROCESS :
A process is the smallest unit of work individually schedlable by an operating system
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READY : In this the process is waiting to be assigned to a processor through a short
term scheduler
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RUNNING : in this process only instructions are executed
TERMINATED : in this process is finished after execution

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