PUUDDUBE “OPERATING SYSTEM OPERATING SYSTEM. Operating system is a program that manages the computer hardware Operating system act as intermediary between the computer user and computer hardware. Operating system designed to provide environment in which user can execute program in convenient and efficient manner. (0S is a resource manager. 4 resources in computer system 1. Process 2, Memory 3.1/0 devices 4. Files 5 provides an orderly and controlled aloocation of all the Hence OS is a Process Manager, Memory Manager, Device PURPOSE: User can’t use an computer unless user have an ‘compile user need an OS & commands from OS x: MN, Pranegwara Rao Dept of CS€, RGMCET 1OPERATING SYSTEM What 05 can do: (user and system) USER VIEW: Tease a. Computer varies according to interface being used. ‘4 b. Users works with PC consisting of monitor, vevbuard ‘mouse and system unit which is designed for one user to monopolize its resources. Goal is to maximize the work that user is performing. . OS designed mostly for ease of use, some attention for perfornighce and none for resource utilization, User sits ata terminal.connected to mainframe or mini b. Other users are accessing same computer through. © Users share resources and exchange information 4d. OS designed to maximize resource utili 3% case Users sit at workstations connected to net b. Users have dedicated resources so. © Users can share resources such af fi d._ OS designed for individual usability 4° case ‘a. Many varieties of hand important. ‘SYSTEMS VIEW: 2. Control Bro ‘execution of user program to’present errors and improper use of bt is concern ‘operation and control of /0 devices. Praneswara Rao Dept of C86, RGMCET v4 Pr On POG Ce Gq ihh1t fel f fief NEL OP HH »to OPERATING SYSTEM Computer System Operation: ‘a. To start running for instance, when it Is powered up or rebooted it needs to have an initial program to run. ‘The intial program or bootstrap program is simple. re It is stored in ROM or EPROM with in computer hardware. Occurrence of an event i usually signaled by Interrupt from hardware or software. Hardware may trigger an interrupt at any time by sending a signal to CPU usually by system bus. Software may trigger an interrupt by executing a special operation called a SYSTEM CALL or MONITOR CALL. ie reac Single-Processor syste! On a single processor system, there is one main CpUfcapable of ex specific processors, such as a disk, key board, ahd’ rocessors run a limited instruction set-and.do.not hey are managed by microprocessors is, BnglesbfScessor system” ' tems = they can share peripherals, mass storage, a Increased Reliability: . Corset power supplies. ‘ upha Some vente If functions can be distributgiAproperiy among several frocessors, then the failure of one processor will not halt the systemgffily slow it down. If we have ten processors and one fails, then each of the remaining processors can pickup a share of the work of the failed processor. The ability to continue providing service proportional to the level of surviving hardware is called “Graceful Degradation”. ‘Some systems go beyond graceful degradation and are called “Fault Tolerant". MN. Praneswota sn otiibtfa comp Dimechine wa torn /ene Foch farckorol ty aver shena loge pit opt haw been desbroyecl > ciyberoney, Will L heap amr 1M Moai Nod —ewrrponends bil“OPERATING SYSTEM Asymmetric Multiprocessing: ‘The multiprocessor systems in use today are of two types. Some systems use asymmetric mult! Processing, in which each processor is assigned a specific task. A master processor controls the systern; the other processors either look to the master for instruction or have predefined tasks. This schemes defines a master-slave relationship ‘Symmetric Multiprocessing: ‘The most common systenis use symmetric multiprocessing (SMP), In which ‘each processor performs all tasks within the operating system. SMP means.that all processors are peers; no master-slave relationship exists between processors. “All moder operating systems Including Windows, Windows XP, Mac OS X and Linux support for SMP. ‘The difference between symmetric, and” asym result from either hardware or software. é Ex: Sun's operating system Suri OS Version 4 provided in Gola) ssymmeticonthesamenaravare; ay, Multiprogramming needed for efficiency ty ase ver cannot Keep CPUand VO deed pusy atattimeh . 2. Mulprogramming orgnies jobs (code dae sochU said of eee 3. OS keeps several jobs in memory et vo {4 Number of obs that canbe kept aera. ey thdhthe numberof obs that can be 5. Asubset of total jobs i stent © One pbstiecedana ni =" ~ 7. When a job haé yait for BS ‘tasklefor Kfar | [0), in a non-multiprogrammed system CPU will sit dystem ‘OS witches to another job tric mutepocas ayhereas version 5 ide where din multiprograme Timesharing ( mu tasking) lotiallertersion in whh PU shes Jobs 50 fequenty that Testi NN cng encanta 1 tes mip jobs by swithing among them. 28 Time sharing OS pr direct,communication between user and system. 3, Regponsettime should bed second 4 theriare Sevethjebs to bring into memory from jb pool anf theres no enough space for allofth ranger mmmust choose among them which is called job scheduling, 5. Having ~e program in memory at same time requires some form of Memory management. 6. if several jobs F@ady to run at the same time, system must choose among them which is CPU scheduling 7. If processes don’t fit in memory, swapping moves them inand out to run 8. Virtual memory allows execution of processes not completely in memory MN, Praneswara Rao Dept of C8, RGMCET 4 4 ey © Gc. ae f © Gx Ce Oe Oe Oe « & & e. © s 2 c e € © a-_ )PERATING SYSTEM Process Management 1, Aprocess is a program In execution I isa unit of work within the systern. Programs a passive entity, process isan active entity. 2. Process needs resources to accomplish its task CPU, memory, VO, files intilization data 3. Process termination requires reclaim of any reusable resources Single-threaded process has one Program Counter specifying location of next instruction to execute Process executts instructions sequentially, one at a time, until c 5. Multi-threaded process has one program counter per thread, 6. Typically system has many processes, some user, some oBefating con one or more CPUS Concurrency by multiplexing the CPUs among the pf Process Management Activities The operating system is responsible for the folowing 1. eating and deleting both utr and pte procesas Suspending and resuming processes Providing mechanisms for Procerfncton tion ¢ion stem running concurrently esses / threads 22 iE a 2 2 z 2. Allinstruction: 3. Memory maf Optimizing CF 4. Memory man ceo ac etic of Rory are crenty beng used ai by whi ding which processes (or parts thereof) and data to move into and out of memory. i memory space as needed lo EX: For Cr = «. oF ta ok the data must be transferred to main memory. instructions must beinmemor CPU to Memory Usage: * Memory vino details of memory being used by each process. * Helps in allocating memory to process when they are executed. '* Memory manager keeps record of the memory used by application while they are running and memory that re or unused, Memory Allocation: * Process needs memory it requests OS for memory space, If memory is available then OS assigns required memory to process MN, Promeswara Rao Dept of C86, RGMCET‘OPERATING SYSTEM Memory De-allocation: "When process is over memory manager removes process from memory The memory space used by the process is marked free ‘Swapping: "Some process needs more memory than itis available. = The memory manager swaps such process between main memory and secondary storage. * When execution of program stops it releases both main and secondary memory for next process * Next process continue to execute, after the execution is over, program releases memory for other program. = A single program normally swap in and swap out many tifies, until complete program is executed. i) io Storage Managet £2.05 provides uniform, logical view of information storage Oo FO Poe On 08 on ne gic 2. Each medium is controlled by device ( i.e, Varying properties include access speed, caf ‘method (sequential or random) be. File-System management g i g z 3 3. OS activities include Storage allocation Disk scheduling fe. Some storage need not be fast Tertiary storage includes optical storage, magnetic tape Still must be managed Varies between WORM ( write-once, read-many-times) and RW ( readwrite) MN. Pranoswara Rao Dept of C8€, REMCET PPS,t! SULOEDELELELEELOELCELEEECECECEEGEOEGOCCEOCOD OPERATING SYSTEM Protection and Security a. Protection —any mechanism for controlling access of processes or users to resources defined by the os Protection improves reliability by detecting errors. Early detection of errors prevent damage of a healthy system by another system that is malfunctioning. An unprotected resource can’t defend against use by an unauthorized user. ._seeuty-deense of the system aainstinteral and tera atta Prevention of some of these attacks isan OS function for someystems. But for other systems prevention is left for additional sofware. ‘&_Systems generally first distinguish among users, to dete User identities ( user IDs, security IDs) include name User ID then associated with all files, processes of thaluser to determine acc Group identifier ( group ID) allows set of associated with each process, file § : Privilege escalation allows user to’ change to effective ID with more right Real-Tirie Embedded Systems 1. Embedded computers are the mo: alent form of computek in existence these devices are bots t9 VCRs and microwave ovens. ‘are usually primitive and so the 2. They have very spec ‘operating system provi ing systems. 3. Embedded systems.almo: M ing systems. : 4, Arealtime s¥stem is used g 2 processor are the flows¢ ws, it n used as a controlled device in dedicated its have been placed on the operation of, 8. Ex: system ye scientific experiments, medical imaging systems, industrial control systems anid certain display systems are real-time systems 9. A real-time syéltm functions correctly only if it retums" the’ correct: result within its time constraints MN. Praneswara Rao Dept of O86, RGMCET 7OPERATING SYSTEM Multimedia Systems 1. Most operating systems handle conventional data such as text files, programs, word-processing documents, and spreadsheets a recent trend Is the incorporation of multimedia data into computer systems. . 2. Multimedia data consist of audio and video files as well as conventional files. These data differ from conventional data in that multimedia data—such as frames of video—must be delivered (streamed) according to certain time restrictions (for example, 30 frames per second). 3. Applications include audio files such as MP3 DVD movies, video conferencing, and short video clips of movie previews or news stories downloaded over the Intefiet. Multimedia applications ‘may also include livé webcasts (broadcasting over the Worl Jeb) of speeches or sporting events and even live webcams . 4, Multimedia applications need not be either aualo or vide rather, a Milt often includes a combination of both. For example movie may consist of separate audio and video tracks 7 a, 5. Increasingly, Multimedia applications bei es roiltasfer dees, including PDAs and cellular telephones. NB For example, a stock trader may have stock quotes delivered witblessly afin real time to his PDA. Hand ‘+ Handheld systems include persona 4), such a Palm- Pilots or cellular telephones with connéeti , + Developers of handheld e many challenges . + First issue “em of suth devi . | ©. Forjexample, a PDA Is a i ches in width, and it weighs less ~ than one-half potihd. Due to, this limited size, most handheld devices havea small amour of mei lude slow processors, and feature small display screens. held devices Rave between §12 KB and 8 MB of memory so the operating ©. Faster Bkocessors require more power, in a handheld device" would require a larger battery that would have to be replaced (or recharged) more frequently. To minimize the size of most handheld devices, smaller, slower processors which consume less power are typically used © last issue for handheld devices is the small display screens typically available. A monitor for a home computer is up to 21 inches, the display for a handheld device is often no more than 3 inches square. ‘©. Tasks, such as reading e-mail or browsing web pages, must be condensed onto smaller displays Pranoswara Roo Dept of C88, RGMCET @ Oe Oe C«€ Oe O¢€ O~ Ce O« Oc Ce CisOPERATING SYSTEM DISTRIBUTED SYSTEMS. aw 1. Its a collection of processors that don’t share memory or a clock Instead each processor has its | oe ° ‘own local memory ‘ 2. Distributed systems Is a collection of loosely coupled processors interconnected by a 7 ‘communication network . 3. A Processor thinks that Its resources are local and rest of processors and their résources are remote. “ut Processors in distributed system may vary in size and function. wy, | Processors can be referred a sites, nodes, computer machines a ‘Site > to Indicate location of a machine. Host > to refer to specific system ata site The host atone site has resource that another host a Reasons for having distributed systems. 1. Resource Sharing : Number of sites connected to one another, the available at another sit 2. User at B may access a file that resid Resource sharing provides sharing files, pri 2. Corhputation Speedup: 1. Computation can be bdadaatti 2 heeadlin composed of mul fe large autonomous installations the fllure of one of them wil 3. If system €omposed oPsmall machines, each of which i responsible for some crucial system —_ - function, then assingle failure may halt the operation of whole system. 4, With enough redundancy, system can continue operation even if some of sites have failed. 5. Failure of site must be detected by system and steps should be taken to recover from failure. 6. System must no longer use the services of that site. 7. If Function of failed site is taken over by another site, the system must see that transfer is complete. 8. Finally when failed site recovers or is repaired, urd 3) dupkea te Pwsoutices edurdend y= Pajey oie Pano fopenw use should be tegrated back into the system. + MN, Praneswara Rao Dept of C8, RGMCET‘OPERATING SYSTEM 4. Communication: 1. When different sites are comgected by communication network users at different sites can exchange the information. : 2. Advantage of distributed system is that communication can be carried out over great distances. EX: Two peoples located at geographically different sites can work on a project by transferring files of project, logging into each others remote system to run system and exchanging mall to coordinate work. OSSERVICES 5 provide an environment for execution of progi’ It provides services to programs and to users of those programs. Service provided will differ from one 0S to other. User Interface: : 1. AILS have a user interface and can take several forms . 2. One is @ Command Line Interface (CLI) which uses text coffitiands and method foftentering them “into files and those files are executed. Oe 4, Most cortimonly Graphical User Interface Is uséd where interface ys pointing device to direct /0, choose from menu ari: make selecti Program Execution: & 1. Program must be loaded into memory to fv 2. Program must be able to end its execution be aware of possible errors 2. Error may occur in CPU and memory hardware (memory error or power failure) in /O device (parity error or lack of paper in printer)and in the user program (arithmetic overflow, an attempt to access illegal memory location) 3. 0S should take appropriate action to ensure correct and consistent computing MN, Pranoswara Roo Dept of C88, RGMCET eo LLOP AE OHNO NN OHNE EASE 4 POO PPP HHP: iP PPPIPPPP ~ kK— a ©st €u0beggdbts : ‘OPERATING SYSTEM *The function described below exists not for helping users but for ensuring efficient operation of system itself. ‘system with multiple uses can gain efficiency by sharing computer resources among the users Resource Allocation: 1. When there are multiple users multiple jobs rinning at same time resource must be allocated to each of them 2. CPU cycles, main memory, file storage have special allocation code 3. VO devices have general request and release code 4. For determining how best CPU can be used OS have CPU- scheduling ‘of CBU, jobs that must be executed, number of registers available and, 5. There may be routines t allocate printers, modems, USB storage drive ‘Accounting qKGaahoa mh » 1. Keeping Wack oF Which users use how much and what ki ymputer resour 2. This record useful for accounting or for accumulating usa} Meg 3. This is useful for researchers to reconfigure systemmifetimpr cof ing services Protection & Security: 1 In multiuser or networked system user want to Control the use of the thformati 2. When several separate processes exectite, conciiffently it should not "le for one process to sm by means'of password-to gain access to les that consider the speed factors other peripheral devices Ystern to perform an operation for the process. doesn’t execute a specific function in hardware but he control of the processor. t by a process for t ion is ti ja and psw registers in the ia and ipsw registers. joads value of 0 into psw registers which puts machine in system mode with interrupts gs 4, Hardware loads la register from the system call interrupt vector location. This completes the execution of system call instruction by hardware. : 5. Instruction execution continues at the beginning of system call interrupt handler(whose address is in system call interrupt vector location) 6. System call handler completes and executes a return from interrupt (rti) instruction. 7. This restores ia and psw from the iia and ipsw 8. The process that executed the system call instruction continues at the instruction after the system call MN. Pranoswara Rao Dept of C86, RGMCET a(OPERATING SYSTEM ‘An example to say how system calls are used Writing a simple program to read data from one file and copy to another file es of two files a) ae jead characters fro keyboard that defines two files. b) On mouse based & icon based.a menu of file name is usual inwindow. = ‘ °) 4) vey ee 1. Application progtammers design programs according to an Application. Programming Interface 2. API specifies set of functions that are available to an application programmer, including parameters that are passed to each function and return values. 3, 3most API's availabe to application programmers ‘2. Win32,AP! for windows system bb, POSIK API for POSIX based system (all versions of UNDXLINUXIMAC OS) JAVA API fro designing programs that run on Java Virtual Machines 4, Each OS has its own name for each system call MN, Praneswara Rao Dept of CS€, RGMCET 2 | NARA DADDA nn aA DPIPPIPPPPPPPPPPPILLL ELIS HN HP OPO 88.95 bePUSVUoed dd OPERATING SYSTEM '5. Functions that make up an API typically invoke the actual system calls on behalf of application Programs. Application pretrammers prefer programming according to an API rather than invoking actual system calls because 1.Benefit programming according to an API s program portability 2.Application programmers designing a program using an API can expect the program to compile and run on any system that supports the API 3.Actual system call can often be more detailed and difficult to workjWith an API available to an application programmer. he System Call Interface “Lit serves asa link to system which is made available of te it intercepts function cals inthe API and invokes necessary system cll within Re OS, 3A number is associated with each system callisystern Call interface maintain ajtable indexed according to these numbers. 4system call interface then invokes the syst stem callin the OS Regnel andieturns the status of system call and any return value, implBmented or what t does during execution > Nothing to know for caller how system “i > ttneeds to obey the API and undersag .0$ wilde as result execution of system call ‘Types of System calls Process File Information Communications Control Management Management Maintenance PC I “a ea oem | Veco] femee] [asase er mom |\Yose ‘| [sex mee on ee : : Teens |S] spam samen | - [resins] : ; | fess] [eee | com mae MN. Pranesuara Rao Dept of CS€, RGMCET a3OPERATING SYSTEM PROCESS CONTROL: 11. Running program can halt its execution either normally (end) or abnormally (abort). 2. Under normal or abnormal circumstances OS must transfer control to the invoking command interpreter 3. Command interpreter reads the next instruction, 4. In interactive system, command interpreter continues with the next instruction. ‘5. In GUI (graphical user Interface) pop up window alert user to the error. 6. In batch system, command interpreter usually terminates entiraffb and continues with next job. 7. Control cards indicate special recovery actions in case an ef Raye some sisters 8 Commo ears commento manage eect of pag 8. Aprocess or job executing one program wants to a id execute anothehprogram. 10. Where to return control when load program terminates 41. If control returns to existing program whey image of existing program 12, Thus a mechanism is created for one program to call another 13. If both programs continue concurrently) multiprogrammed. % N 14, There's a system call specialy fort 415. If new Job or process controled. 436. Control means ability iinates we mustisave memory shen that event has occurred(signal event) debugging preeram gram to indicate amount of time that program executes. of timer interrupt value of program counter is recorded. gps time spent on various parts of program canbe obtained 1. MS-DOS is an example of Single taking system. 2. It has command interpreter that is invoked when computer is started. 3, Ituses simple method to run a program and doesn't create new process. 4. It loads program into memory, giving the program as much memory as possible. 5, Itsets instruction pointer (IP) to first instruction of program. 6. Program runs and either an error cause a trap or program executes a system call to terminate. 7. Error code is saved in system memory for future use. 8. Small portion of command interpreter that was not overwritten resumes execution. 9. First task is to reload rest of command interpreter from disk. MN, Praneswara Rao Dept of CS€, RGMCET ua BAIPP DPD PAP AAAA DA A DSOPERATING SYSTEM 10. Command interpreter makes previous error code available to users or to next system. Ms-Dos UNIX Atm in nines voor Pre mmeny a gh Free BSD (derived from Berkley UNIX) is an example of fhultitasking ‘As users log on to system the shell of user's choice illrun Shell accepts commands and executes progra De 6. mine the values of various attributes and reset them if necessary 7. File attribute include file name, file type, protection codes, accounting information etc. 8. 9. Two system calls get file attribute & set file attribute are required for this . ‘many more calls for file move and copy. 10. Other OS provide an API that perform those operations using and other system calls 11. If system calls are called by other program then each can be considered an API by other system program MN, Pranoswara Rao Dept of C86, RGMCET aOPERATING SYSTEM DEVICE MANAGEMENT: 1. Process may need several resources (main memory, disk drives, access to file) to execute f 2. Resources willbe granted if they are available and control can be returned to user process else process will have to wait until sufficient resources are available. 3._ there are multiple users the device should be requested frst (Once device is requested it can be read, write, reposition the device 5. After finishing these devices are released. INFORMATION MAINTANENCE: Lb Many system calls is for transferring information between use rn and os ta creat ne al Other system cll may return info about the system. 8 %, fx: Number of current users, version number of O5,,ffount of free memetyor disk space. (0S keeps information about lit process and system calls usedto access hiRinformation. system calls are also used to reset, process quant << attributes and set process ) attributes) & es COMMUNICATION: 2 models for interprocess communication 1. Message passing model ey 2 Shared mem model 7 Message Passing Model: x Exchanges information with one another to cide Message can be exchaiged between p bess either directly or indirectly Or Before communication star ection myst be Obened. Other commusigstor must b&)knowtlemayhbe other process on same system or process on another system connected by Ren Each compute in networks host ane which has an IP address ie and nae i translated to identifier by which OS can refer the itipermit for communication with ACCEPT CONNECTION call, 10. Exchange offinessage is done using READ MESSAGE & WRITE MESSAGE SHARED MEMORY MODEL: 1. Process used shared memory CREATE & shared memory ATTACH system calls to create and gain access to memory owned by other processes. 2. 0S prevent one process from accessing another processor's memory 3. Shared memory requires 2 oF more process to remove this restriction. 4, They can exchange information by reading and writing data in shared areas. 5. Processors responsible for ensuring they are not writing to same location NOTE: message passing is useful for exchanging smaller amounts of data shared memory allows maximum speed and convenience since it is done at memory speed. MN. Praneswara Rao Dept of C56, RGMCET A .‘OPERATING SYSTEM Communication CreatePips© Groaters teNeppins © NapviewosFaiec>, Protection SeeFaresecurityO EniciiaiisesectsityDescriptorO SoeSecuritybencrapeorarone es © MN. Praneswata Rao Dept of C8, RGMCET wv‘OPERATING SYSTEM Operating-System Structure Simple Structure 1. Operating systems started as small, simple, and limited systems and then grew beyond their original scope 2. MS-DOSis an example of sucha system 33 wel defi vel OS Structure ito r slo ro" ite tay Sx wr He 3 or ai ks wit? c Y) s.008 devices arivere % SE mo ae tase boy modules carefully 4. In MS-DOS, the interfaces and leVels Of functiaalty ae not well separ 5. Application programs are able to access) (0 routines to write directly to the display - and disk drives, this : , grams, causing entire system 2. Ie was written to provide the most funcl fay inthe lea pace, so,iGwas not divided into tp ¢ 6 | ( Sere ISHS... Terminal controllers, Device controtters Memory controtiers, la ommeae Sue eaee meyeeay seme ply Pe comes lg actua ra voinaaltninmerenpeears ° 18. Thekerneis further separated into a series of interfaces and device divers 9. Everything below the system call interface and above the physical hardware Is the kernel 10. The kernel provides the fle system, CPU scheduling, memory management, and other ‘operating-system functions through system calls. c 11, This monolith structure was efit to Implement and malta. ; MN. Praneswara Rao Dept of C58, RGMCET aa QPL\PPFIIPIPAPAPAPAA PAL IST ELBAAS“OPERATING SYSTEM Layered Approach ). The bottom layer (layer 0) is . Atypical operating-system layer—say, layer and a set of routines that canbe invoked by higher-level ayers layers . This approach simplifies debugging a executes an I/O operation, it executes a system call that is trapped to ‘the memory-management layer, which in turn calls the CPU-scheduling. then passed to the hardware. MN, Praneswara Rao Dept of CS, RGMCET 19. Po meee gl Bt on wh pe : t TL wie b she 0qe wre Ge Kewel tc on boc “re Microkernel — phovdos Be cHiorel:bies 1. As UNIX expanded, the kernel Neon large and difficult to manage 2, Mach OS modularized the kernel using the microkernel approach 3. This method structures the operating system by removing all nonessential components from the Kernel andimplementing them a system and ser evel programs 4. Little confusion regarding which services should remain in the kernel and which should be implemented in user space 5. Microkernel’s provide minimal process and memory management, in addition to a communication facility. 6. The main function of the microkernel is to provide a communicatior progam and the varous series that ae aso runing j provide by messoge posing’ 7. One benefit of the microkernel approach is ease of ext 7 J» facility between the client s* space. Communication is 8. All new services are added to user space and conse modification of the kernel 9. When the kernel does have to be modified, the because the microkernel is a smaller kernel y 10. The resulting operating system is easier to are design to another 411. The microkernel also provides more security and reliability ) i 5 : 3 i 2._ uses dynamically load: * Solaris, Linux, and Mac} 3. Solaris operatir A Scheduling classes : surorsell ot loo Wool 8 Hove b. File systems netahton . Loadable system calls wd tay Lov hes Photario t & implementations of UNIX, such as is organized around a core kernel with 9} rrears be yellow machdes: structive. jn0S St wes 00PT 1 Geb * Vio daden 33232332 a |. Executable formats STREAMS modules Miscellaneous Device and bus drivers Lapel eal. MN. Praneswara Rao Dept of C86, REMCET ea peal.OPERATING SYSTEM allows the kernel to provide core services yet also allows certain features to be Implemented dynamically example, device and bus drivers for specific hardware can be added to the kernel, and support for different file systems can be added as loadable modules. ‘The approach is like the microkernel approach in that the primary module has only core functions and knowledge of how to load and communicate with other modules; but it is more efficient, because modules do not need to invoke message passing In order to communicate. The Apple Macintosh Mac OS X operating system uses a hybrid structure Mac OS X (also known as Danvin) structures the operating system using a layered technique ‘where one layer consists of the Mach microkernel s providing a graphical arily of the Mach microkernel for remote procedure calls (RPCs) and jessage passing; and thread scheduling MN. Praneswara Rao Dept of C86, RGMCET 2OPERATING SYSTEM OPERATING SYSTEM GENERATION Designing, coding and implementing an OS for one machine at one site is simple. But OS id designed to run on any machine at variety of sites with a variety of sites with a variety of peripheral configuration 0 traditionally written in assembly language, OS now can be written in high level language can be written faster, more compact, easier to understand and debug (0S is far easier to port fit is written in high level language ‘To generate a program we use a special program called SYSGEN 'SYSGEN program obtains information concerning specific configur ‘The SYSGEN program reads from given file or asks the operator of system for information about configuration of hardware system or probes the hardware directly ine what components are there ee Information includes &. >What CPU to be used? What options (extended inst é sets, floating my arithmeticjare installed? For multiple CPU systems each CPU must be deterfhined >How much memory is available?, » Some systems give this value by refrringeach my location after Rf cao non et addres fault generated ‘his procedure defines final legal address ar jount Gf memory available >What devices are available? System need to know how number, the devices type and m >What 0S options a or ‘These options or values might include CPU scheduling alge by the device number, the device interrupt ae ss to be used? sof which sizes should be used, what type of > pata deciafations, initializations and constants along with conditional compilation, produce an output object version of 0S ~~, > system descriptionican cause creation of tables and selection of modules from precompiled library 3 These modes relied together to form generated 0S > Selection allows library to contain device drivers for all supported I/O devices but only those needed ae linked into 05 Because the system isnot recompiled system generation i faster 5 atother extreme, allcode is always part of system; selection occurs at execution time, rather than at compile or link time MN, Praneswara Rao Dept of C8, RGMCET 2 a0 ALP IPD Apa Pip pplODLDAOL FT OL LO pow on fH * SHR‘OPERATING SYSTEM SYSTEM BOOT (Once OS is generated It is made avallable for use by hardware But how hardware knows where Kernel is or how to load Kernel starting a computer by loaiiing Kernel is known as booting the system. ‘Small piece of code Boot Strap Program Or Boot Strap loader located the Kernel. ‘This program loads Kernel into main memory and starts its execution. In some system it's a two step process simple Boot Strap Program loader fetches more complex boot programy from disk, whith in turns loads the Kernel When system Powered up or rebooted - + IR loaded wityh predefined memory location and execution starts fro aye That location contains Boot Strap Program that yeed ho initialization and cant be infected by virus > Tasks of Boot Strap Program ‘a.Runs diagnoOstics to determine state of m: with booting steps initializes all aspects of system, from CPU ri Memory 1. PDA's ,cellular phones, game consoles rugged operation. using EPROMS. 3. ROM also called as Fi . er than executing code in RAM ‘to RAM for faster execution Clustered Systems Clustered systems gather together multiple CPUs to accomplish computational work. Clustered systems differ from multiprocessor systems, however, in that they are composed of two or ‘more individual systems coupled together. Clustered computers share storage and are closely linked via a local area network (LAN) or a faster interconnected such as InfiniBand, ‘Clustering is usually used to provide high-availability service; that is service will continue even if one or ‘more systems in the cluster fall. MN. Pranoswara Rao Dept of 56, RGMCET 23OPERATING SYSTEM 'n eosin can be structured asymmetrically or symmetrically, applications na wutetin One machin isin hotStandby mode while the ther Is running the fale here are hotstandby host machine does nothing but montor the active server. the server Insymmecea: tana host becomes the active ere . mode amass two OF more hosts are running applatins, andar monitoring each ater. This usly more efficient, as it uses all ofthe available hardware. It does require that more than one application be available to run, Other forms of clusters include parallel clusters and clustering over a wide-area network (WAN). Parallel clusters allow a multiple hosts to access the same data on the shared stGge. To provide the shared access to data, the system must also supply access control on the lockfng to ensure that no conflicting Perations occur. This function, commonly known as Distributed Lock Batch Systems? 1. Early computers were physically enormous machines{un from a console 2. Common input devices were card readers and tape drives 3. Common output devices were line printers, the res, and arpunches 7 Gord nv rane tcs es care ists Migs nani sealacd or program, the data, and some control information about the nal submitted itt the computer operat 5. Job was usuaily in the form of punct ‘output appeared which consist the contents for debugging ; 6. Present computers traf gga cal one job tothe next operating system wae 7 SINE, operat ther jobs with similar needs and ran them through operator would sort programs into batches with similar juter Became available, it runs each batch and the output from each job ‘the appropriate programmer S 2 sds of the mechanical /0 devices are intrinsically slower than read 1200 cards per minute (or 20 cards per second). There is difference and its /o devices 111. Even 1/0 devied\speed increased, CPU speeds have increased to an even greater extent, so the problem was not unresolved 112. The introduction of disk technology allowed the operating system to keep all jobs on a disk, rather than in a serial card reader MN, Praneswara Rao Dept of C56, RGMCET a PHONO HM ONO NHN aD’ PP Poe ” 2PPLPAISLPLAPP PPP LP