OPERATING SYSTEM

(OS)

OPERATING SYSTEMSoftware & systems

The OS is software that controls the execution of computer programs and which may provide scheduling, debugging,I/O-Control, Accounting, Compilation,Storage assignment, data management and related service.

Defn:-

TYPE OF OPERATION SYSTEMWINDOWS

Microsoft Windows: 95, 98, 98-Second-Edition

Microsoft Windows: 2000( Professional & Edition)

Microsoft Windows: Millennium (Me)

Microsoft Windows: Network Server

Microsoft Windows: XP(Professional & Edition);

(XP-Service-Park I,II,III,IV)

Microsoft Windows: XP-Vista/Microsoft-Vista

LINUXDebian

Red-Hat

Ubuntu,Kubuntu,Xubuntu,edubuntu

Fedora-Core

OPERATING SYSTEMOPERATING SYSTEMComputer programs,procedures,rules and possibly associated documentation and data per pertaining to the operation of a computer system.

Noted from AuthorWithout software,a computer is basically a useless lump of metal,Silicon and Plastic.

System Software Which manages the operation of the computer itself.

Application programWhich solve problems for their users.

APPLICATION SOFTWARE cont... May be mass produce for the consumer or business market or may be developed specifically to meet the need of a particular customer or set of user

SYSTEM SOFTWARE The most fundamental of all the system programs is the OS.

SYSTEM SOFTWARE The most fundamental of all the system programs is the OS. The main roles of the OS are to:

Hide the complexities of the hardware from the user

Manager the hardware resources in order to provide for an orderly & controlled of the Processor,Memories and peripherals amongst the various application and system programs completing for them.

OTHER SYSTEM PROGRAM

INCLUDECOMPILER translate the program that programmers write (source-code)into a code that the compiler understands (object-code).

LINKER Which combine several components of object code to create a system from several programs.

EDITOR Simple text editor that enable programmers to create and Edit their source code.

INTERPRETER Operate to interpret commands from the keyboard,or other input device and instruct the computer to perform a specific function

OPERATING ENVIRONMENTSOS that does not focus on some form of desktop windowsWe can consider each of these development stages as providing an operating environment for business use. Some of these are now obsolete,but you should not automatically assume that an OS that does not focus on some many situations where such an approach is inappropriate. The environments we will consider are:

Single-User,single process;Batch;Multi-programming;Interactive;Multi-access;Multi-access and batch;

Multi-tasking and real-timeNetworked and client-server systems;Distributed computer systemsmulti-processing

SINGLE USER,SINGLE PROCESSThe start-up and shut-down after

Job major activity that was normally carried out by PC operation.

The program would then be started and would run until it was completed. The result of the run would typically be

printing of a report.

BATCHTo improve the efficiency of the computer a series of job could be set up one after another (Job Streaming)

A better approach was to read the punch cards onto magnetic tape & then load the tape containing perphaps hundreds of jobs onto the computer and run them one after another.

CONT.....Operator relieved from the constant loading and unloading of Jobs. The OS needs to after the transition between Jobs and ensuring that the result are separated for later printing.Business application that suitable for running in batch-code include

payrollsome intensive calculationsdata backup and archiving

MULTI-PROGRAMMINGIs the apparently simultaneous execution of several programs all of which are held in memory.-A multi-programming OS balances the sharing of the processor among the application programs in order to achieve a good service to all. Include-minimise unused CPU time.-reduce the incidence of peripheral-bound operations.

-Minimise total elapse time.-Prevent single programs from

dominating the CPU.

INTERACTIVE

An interactive or on-line system on the other hand,is one in which the user interacts directly with the system to supply commands and data as the application program undergoes execution and receive the results if processing immediately (Microsoft Os Ms-Dos)

MULTI-TASKING AND REAL-TIME

May be applied to both Single and multi-user operating Systems. REAL-TIME Os are characterised by FOUR requirements-they have to support application programs which are nono- sequential in nature,i.e. they are continuous process and do not have a START-PROCESS-END Structure

-They have to carry out processing and produce a response within a specified interval of time.

-They may have to operate reliably in a fail-safe mode,if they are employed in safety critical application.

Main function of an OS Manager the computer

resources for their optimal

utilisation.

Perform housekeeping

operations.

STORAGEMemory management,to ensure that the processes that require memory can obtain it when they need it.

PRIMARY FUNCTIONS OF AN

OSPROCESSESprocess management, which supports scheduling of processing and interprocess communication and detection and prevention and prevention of deadlocks.

INPUTI/O management,to ensure that the system is not held up waiting unnecessarily for input and output to take place.

DATAFile management,to ensure effective control over secondary storage media, including space allocation and naming of files.

SECONDARY FUNCTIONS OF

AN OS

User AccountingIn many OS it is possible to keep record of the usage that individuals have made of resources such as CPU,Disk Space,Printer pages.

LOGGINGMemory The Os may keep comprehensive record of all the system action that relate to a particular program,or to all program.- Discovering the reason for failure and to predict

future patterns of system utilisation.

UTILITY SOFTWAREUtility program of routines carry out certain well defined procedure that are common to virtually all application & installations.Her are some common UNIX examples:awk-pattern matching,data transforming,report

generationcal-display calendars in various waysfind-find a file and then carry out some action.

Some of WINDOWSNotepad-Simple and change.Scan disk-Check disks for error.

OPERATIONG SYSTEM PROCESSESThe concept of process is central to the study of OS's We saw earlier that it is a program in execution. It is necessary to distinguish between a program in execution. It is necessary to distinguish between a program and its execution in this way for three reasons.Several user may each have a copy of the same program running in memory at the same time;.

a single program may be under execution multiple timessimultaneously,E.G when users share copy of a complier;.

when a program is loaded into main memory ready for execution its form changes;.

PROCESS MANAGEMENTRunning (actually using the CPU)Runnable (able to run,but temporarily stopped by the OS to allow another process to run)suspended (unable to run until some external event occurs)

RUNNING

SUSPENDED

RUNNABLE

PROCESS COMMUNICATIONThere TWO main method of process communication

Sharing of common storage;message passing.

In some operating systems,processes that are working together may share some common memory that each one can read and write. The shared may be in RAM or it may be a shared file-the location of the shared memory does not change the nature of the communication

Various scheduling method are available to assist the scheduler in its task of selecting the next process. Some typical ones are:

shortest Job first; shortest remaining time; Round-robin-in which the process that is at the top of the queue is run for a fixed period of time then put to the bottom of the queue. Each process gets an equal amount of time until it finished.

DEADLOCKDeadlock-Is a potential problem in any operating system.IT occurs when a group of processes each have granted exclusive access to some resources,and each one wants yet another resources that belongs to another process in the group. all of them are blocked and none will ever run again.

UT

B

A

Figure above shows a deadlock situation Process A is waiting for resources T,which is currently held by process B;

Process B is not about to release resource T because it is waiting for resource U, held by A;

Both processes will wait forever.

User Interfaces to the OSThe user interfaces is that part of a computer through which a human user and the computer communicate.User interfaces can be classified as:

Job Control Language (JCL)Command Line Interface (CLI)Graphical User Interface (GUI)