Sissejuhatus informaatikasse IT Kolledzh TTÜ 2003 T Tammet IT

Sissejuhatus informaatikasse IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk -1 -

Miks opsüsteem? Opsüsteemi põhieesmärgid: Pakkuda programmeerijale valmistehtud standardtükke. Võimaldada kasutajal arvutis ühtemoodi ja harjumuspäraselt tegutseda, sõltumatult sellest, mis programmid tal arvutis on. Miks opsüsteem? Arvutit saaks programmeerida ka ilma opsüsteemita. Sel juhul: oleks iga programmi tegemine palju raskem kui opsüsteemi olemasolu korral. kasutajate jaoks näeks eri programmid väga eri moodi välja. IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk -2 -

Mida opsüsteem enamasti teeb? Oskab kettalt programme lugeda ja neid käima panna. Oskab programme seisma panna (lõplikult või ainult väikese pausi jaoks) Oskab kettale faile ja katalooge kirjutada ja sealt neid lugeda. Oskab välisseadmetega (printer, monitor, klaviatuur jne) suhelda. Oskab võrguga suhelda. jne Kui opsüsteemi ei oleks, peaks iga programm kõiki neid asju ise teha oskama! IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk -3 -

Naked machine What is there in the naked machine (unclothed by an OS)? CPU (registers, opcodes), Memory (may be several chunks), Devices (mapped to memory locations, able to transfer data to and from memory). IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk -4 -

Definitions of OS!? … Extended machine, or virtual machine. Takes the basic hardware, and provides additional layers of functionality. The virtual machine is usually simpler and more consistent than the real machine. Practically, additional layers will build on the lowest-level ones, providing a rich programming model for the applications software (which in turn provides a 'virtual machine' to the user). Resource manager. Allocates scarce resources, like disk space, memory, processor between competing processes and users. Each process thinks that it has its own machine (its own files, its own printer, whatever). In a way, this is also extending the machine (in order to appear to be many machines). Anything which runs in the computer's privileged mode, or supervisor mode. Typically most modern processors have two or more operating modes, user and supervisor. In supervisor mode, able to access all of memory and all hardware. IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk -5 -

Definitions of OS!? The software which is supplied with the machine. Often includes many things not traditionally considered part of the operating system, like GUIs, editors, Web browsers, and stuff. A platform on which other software can run. Lots of platforms are not operating systems (like Netscape Navigator, or Microsoft Word). Java is almost an operating system. Provides many services commonly associated with Operating Systems, like managing multiple concurrent processes, and providing access to files. IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk -6 -

Operatsioonisüsteemide arengulugu Arvutid ilma OS-ita Batch processing süsteemid Multiprotsessing ja terminalid - UNIX Personaalarvutid - IBM, Xerox, Apple, DOS, Windows IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk -7 -

Operatsioonisüsteemi roll IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk -8 -

OS layers IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk -9 -

Operatsioonisüsteemide omadused Funktsionaalsus Protsesside haldamine Mälu haldamine Failisüsteemid Võrguprotokollid Kasutajate haldamine IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 10 -

Interrupts The interrupt handler must save the machine state, do some processing, then call the process scheduler and dispatcher. When an interrupt occurs 1. the processor hardware makes a quick copy of the program counter and CPU registers 2. the hardware switches to kernel mode and jumps to the interrupt service routine 3. the ISR is usually very short. It may inform a device driver that it received the interrupt; it may just increment some clock counters. 4. next the ISR calls the scheduler, which decides which process to run 5. the scheduler calls the dispatcher, and new process (or maybe the same process) resumes where it left off An important goal of the OS is to hide interrupts from the user---and from user-level processes. IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 11 -

Processes have their own memory areas IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 12 -

Multitasking and scheduling IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 13 -

Parallel running of processes is a movie-like illusion http: //w ww. yout ube. com /wat ch? v =qq smei __k m. Q IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 14 -

Running programs in parallel Each program gets ca 0. 01 sec time slice, then another runs, etc, cyclically. Slices vary: from 0. 005 to ca 0. 1 - 15 -

Processes wait and run – when chance comes IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 16 -

Main scheduling algorithm goals Fairness. Treating users fairly: everybody gets some time to run Respecting priority. That is, giving more important processes higher priorit Efficiency. Do not spend excessive time in the scheduler. Try to keep all parts of the system busy. Low turnaround time. Minimize the time from the submission of a job to its termination. High throughput. Maximize the number of jobs completed per day. Low response time. Minimize the time from when an interactive user issues a command to when the response is given. Repeatability. Non-random, predictable behavious Degrade gracefully under load. - 17 -

Process lifecycle in more details IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 18 -

Memory handling Defines - which application occupies, which part (block/segment) IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 19 -

Memory handling Organise virtual memory to fit all application memory into existing (static memory size) Consider we have App 1, App 2, App 3, App 4. App 1 occupies section 1, App 2 occupies section 2, App 3 occupies section 3. What we do with App 4? ? All those Applications are not runnig at the same time (see previous slides or processes handling). So we could store another application memory to HDD and reuse that space fro Appl 4!!!. . . and then when this other (lets say App 1) is activated move App 4 memory to HDD and restore App 1 memory (before activating App 1 – so it is not visible for her). This process is called swapping. Decrease number of swaps: For example if the execution sequence is App 1, App 2, App 3, App 4, App 1 and all apps requires the same block then instead of replacing App 1 with App 4 we could replace App 2 with App 4. The last case App 4, App 1, App 4, App 1 will not require swapping App 1 and App 4 permanently. Instead App 2 will be at HDD and both App 1 and App 4 in memory IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 20 -

Memory handling T. Tammet IT sissejuhatus loeng 8 lk - 21 - a, b, x are integer, so requires 2 bytes, so: a=> address 000 (i. e. bytes 000, 001) b => address 010 (i. e. bytes 010, 011) c => address 100 (i. e. bytes 100, 101) IT Kolledzh/TTÜ 2003 a, b, x since we use: b=2; x=3; a=b/x; App is loaded starting from 11011000 address, so: a starts at 11011000 b starts at 11011010 c starts at 11011100

IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 22 -

IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 23 -

IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 24 -

Cache ja mälu hierarhia Pilt selgitustega tahvlil. Alternatiiv: loe vastavat kohta lisamaterjalist Computer Systems: a programmers perspective IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 25 -

Operatsioonisüsteemide omadused Kasutatavus Liides: käsurida (CLI), graafika (GUI) Olemasolevad rakendused, teenused Vajalik riistvara Haldusvahendid, kaughaldus Stabiilsus Skaleeruvus Tugi Hind IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 26 -

Suured praegused opsüsteemid, nende põhirakendusvaldkonnad ja umbkaudsed turuosad • Windows (Microsoft) • Tava-arvutid (92%) • Serverid (36% servereid) • Mobiilid (alla 1% mobiile) • OS X ja i. OS (Apple) • Mobiilid (iphone 25% / ipad 36 %) • Tava-arvutid (mac, 6. 5%) • Linux (vabavara) • Mobiilid (Android, 21% mobiile) • Serverid (63% servereid) • Pisiseadmed (domineeriv) • Tava-arvutid (1. 5 %) • BSD (vabavara) • Serverid - 27 - Mõned väiksemad: • • • Symbian (mobiil) Blackberry (mobiil) Bada (Samsungi mobiil) Tiny. OS (pisiseadmed) z. OS (IBM mainframes) Unix

Android OS structure - 28 -

Süsteemi koguhind Installeerimise kulu Haldamise kulu Riistvarast või OS-ist põhjustatud rikutud andmete taastamise kulu Välja- ja ümberõppe kulud Riistvara Tarkvara litsentsid Tehniline tugi Tarkvara upgrade Riistvara upgrade Seisaku põhjustatud kasumi kadu IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 29 -

Näide: süsteemi hinna kujunemine IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 30 -

Failisüsteemide võrdlus IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 31 -

Pääsuõigused NTFS failisüsteemis Iga faili ja kataloogiga on seotud pääsuõiguste nimekiri (ACL Access Control List) ACL on nimekiri pääsuõiguste kirjetest (ACE - Access Control Entry) ACE koosneb: kasutaja, grupi või arvuti nimest pääsuõiguste loetoelust Kui kasutajale, ega tema grupile ei ole mingi ressursi juures vastavat õigust antud, siis pole tal võimalik seda ressurssi kasutada IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 32 -

POSIX pääsuõigused d r w x faili omaniku grupi tüüp õigused teiste õigused r lugemisõigus w kirjutamisõigus x käivitamisõigus s t set. UID, set. GID sticky bit IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 33 -

Virtualiseerimisvahendid PC riistvara emuleerimine Vmware Olemas nii Linux, kui Windows versioon Eri versioonid töökoha ja serverirakendusteks Virtual PC (Microsoft) Parallels (Mac. OS) Virtuozzo. Open. VZ Vserver XEN App 1 App 2 App 3 UML Linux QEMU Kliendid saavad täiesti oma serveri Serverite virtualiseerimine Linuxipõhised virtualiseerimisvahendid Õppeotstarbel Testkeskkondadeks Tootearenduses ning kasutajatoes Server - hosting Riistvararessurss jaguneb mitme serveri vahel Lihtsustub riistvara hooldus Virtuaalservereid saab ümber tõsta teisele riistvarale Teenuste eraldamiseks - igale teenusele oma server turvalisus Windows NT VMware Free. BSD VMware Linux Bare hardware IT Kolledzh/TTÜ 2003 T. Tammet IT sissejuhatus loeng 8 lk - 34 -