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p.specht
 | The installation the Betriebssystems on one computer is in the rule a einmalige Anfangsaktivität, in the Contrast to that almost alltäglichen Systemstart:
like a PC (personnel computer) bootet
(fountain: Diverseste internet-pages + Gedächtnisrudimente)
Boots are boot, very Reiterstiefel with Schlaufen dran, undertow. boat-Straps. who reminds not on The Münchhausen-story, as the itself on its own boat-Straps from the swamp pulled! Similar paradox verläuft the Start one computers, engl. abgekürzt "booten". The is first once one bunch completely dummer electronics.
Why the Topic interssiert?
I had a PC via eBay-Kleinanzeigen bought, the as "bootet nicht" ausgeschrieben was. it set itself out, that its Bootdisk not okay war; with a new erstellten USB-Stick has it then functions. only: To I there on it coming, lasting it long! what at Booten one PCs everything happens, is integrally beautiful komplex, and my know moreover stammte from 1995 ...
PCs, then and today
"Alte" PCs Start with the BIOS (basic input/output system) in the flash-memory (rewriteable read only memory) and in the later course with the Bootloader from MS-DOS-times.today runs with the UEFI (Unified Extensible Firmware interface), one grafisches "BIOS", in the one The Order the Bootmedien with the mouse einrichtet.
The boat-process the Ur-PCs, the IBM PC 5150
How it with de-facto-Standards so is, having it any IBM-kompatiblen PCs übernommen, so one so quite the same Vorgehen To into Pentium-generation into see can. the only, the really differently is, concerns The physikalische Speicheradresse, on the The CPU with the Abarbeitung begins.
with one IBM-PC began the Startvorgang with the process the Power-Schalters, mostly hinten right on the power adapter. Zit: "Aus visibility the Informatikers are Netzteile gruselige locations, circa from the thrill, The Humans dead power, The thrills To produce, The electronic Bauteile prompt."
inside the Netzteils count The regulate the analogen world: thrills approach itself ihren Sollwerten kontinuierlich on, Oszillatoren swing itself one. with the from digitaler visibility undefinierten Zwischenwerten can the remainder the PCs not plenty begin, and so the power adapter at started something Vorsprung get. first if The thrills steady are, must the remainder the PCs loslaufen, gesteuert by the signal "Power Good" the Netzteils. with the altgedienten AT-Steckerbelegung befand itself this signal on Pin 1 the P8-Steckers and carry there usually The colour orange.
The CPU (Central Processing Unit) runs go
for the next step look we The Intel-8088-CPU on, The known whom first PC powered has. If these with thrill keeps becomes (or. a Reset durchläuft), begins tappt im dunkeln The process of code on the address FFFF0H. this is the beginning the highest 16 byte the whole then Adressbereichs, the itself of 00000H To FFFFFH erstreckte (20 bit => 1 MByte).
Why just there, instead of in front with 0? because itself in the area of 0H To 3FFh with this Prozessortyp The Interrupt-Sprungtabelle befindet, means those Sprünge The with the process one interrupts needed go. probably watts therefore something effizienter or eleganter (kürzere Sprünge into
Programmcode?). and because the Booten very plenty seltener stattfindet as the Perform one interrupts to Laufzeit, yields it sense, on the häufigeren drop To optimize.
with later CPUs with größerem Adressbereich watts the schema to maintain, The process begins into last 16 byte. that is one 80286 begins with the process on address FFFFF0H (24 bit) and a 80386 on address FFFFFFF0H (32 bit).
but what can with 16 byte begin? not plenty, therefore standing there only one Sprungbefehl to that Einstiegspunkt the BIOS-Program, z.B. FE05Bh on the example the IBM PCs with 8088-CPU.
for any, The The Eleganz this Konzepts understand want:
* The CPU begins at a solid address, The of processor-manufacturers into CPU burned watts. The CPU "weiß" there not yet, whether tappt im dunkeln one PC, a washing-machine or a Ölpumpensteuerung becomes.
* The PC-manufacturers (OEM - Original Equipment Manufacturer) places adressmäßig first once a ROM-Baustein there there, which Content himself definiert. on the solid address standing one Sprungbefehl to that OEM-specific Programmanfang.
the BIOS and the Bootsektor
the BIOS the Ur-PCs lying in the area of FE000H To FFFFFH (8192 byte), where the beginning not executable is and items as Teilenummer and copyright-indicated contains. ex FE05BH goes the Programmcode go, the whom PC first once in a arbeitsfähigen status bring. moreover heard z.B. the Initialisieren (= in a definierten status bring) the internen and external hardware. Sometime later comes the momentum, on the The control of BIOS to that Betriebssystem übergeht. still where is this?
it follows again a combination to the schema "fester place, dynamischer Sprung". we weg of it from, that The Bootreihenfolge so tuned is, that of first drive (Kennung drive0) launched go should. the BIOS loading whom first sector (fester place on the disk) into memory and lead it from. thereby is it a convention, that the code on The address 7C00H loaded becomes. these important for Systementwickler, so absolute Sprünge and data on the right place sought go (Similar the org 100h at Assemblieren of middle-aged .COM-Files).
The first sector the Disk, too Bootsektor called, begins now with the dynamic plunge. Why the, if the code still complete discretionary is? because at the beginning the Disk too yet dateisystemspezifische Information How the Dateisystem self (type, Version), The Geometrie the Datenträgers (streaming in physische Sektoren and segments), name the Mediums, etc. stored are. this must namely too anytime auffindbar his and power therefore ditto of "fester Ort"-principle use.
General: with more Computern (including Großrechnern) sounds The suitable Bezeichnung for a boat-process too Initial Program Load (IPL) and a Reboot re-IPL. the Booten one Betriebssystems begins with a very small Program. once this into computer loaded watts, there The Programmsteuerung ex, sodaß the entire Betriebssystem nachgeladen and is The Control the Rechners undertaking.
means:
* once the computer eingeschaltet becomes, becomes the BIOS (Basic Input-output system) on the system-ROM (Read-only Memory or flash-memory) launched and undertaking first The Control the Rechners.
* the BIOS launch first of all a Power-On Self Test (POST), circa sicherzustellen, that any Computerkomponenten betriebsbereit are.
* Then the boat-Program loaded, around the Betriebssystem into main memory loading to.
* in the next step seek the boat-Program on one drive or angeschlossenem USB-unit to boat-Files for the Betriebssystem. Sofern there no boat-Files found go, becomes The Search on the Festplatte continued. These boat-Order can in the BIOS set go.
* after the boat-drive identify watts, screen the BIOS as nächstes whom first sector and copies data into RAM-memory the computers. These Information and data go too as boat Record or master boat Record marks.
* subsequently loading the BIOS whom boat Record into main memory. The boat Record contains one Program, the the BIOS now uses and the control over the computer undertaking.
* The boat Record loading The anfängliche Systemdatei (for DOS-systems in example IO.SYS) of a drive or the Festplatte into main memory.
* The ursprüngliche File (in example IO.SYS, The one Program namens SYSINIT contains) loading then whom remainder the Betriebssystems into main memory. on this place becomes the boat Record not any more needed and can through others data overlay go.
* The ursprüngliche File (in example SYSINIT) loading a Systemdatei (zB MSDOS.SYS), also with the BIOS works can.
The of beginning the Bootsektors angesprungene code is now betriebssystemspezifisch and Done whom remainder. How this remainder looks depends naturally heavy of Betriebssystem ex. in the subesquent viewing I one MS-DOS-Betriebssystem - the was then yet on the simplest:
MS-DOS launch
Note: the could too IBM PC-DOS hot, The differences are here marginal and in the integral on The name the Files dull. MS-DOS exists from several Files. directly visible for user is COMMAND.COM (ex the 64bit-generation as cmd.exe emuliert), this is the Console-Befehlsinterpreter. furthermore there yet Systemeigene Gerätetreiber analog To IO.SYS and MSDOS.SYS (DOS-Kernel), The usually cache are (File-attributes s, H and R). The code from the Bootsektor loading the first three Sektoren of IO.SYS into memory and lead tappt im dunkeln from. this beginning of IO.SYS loading whom remainder to, initialized The tools and drives thereafter with the Loading and Perform of MSDOS.SYS away. thereafter are The functions for "normalen" Access to the Dateisystem available and the Abarbeitung of CONFIG.SYS and finally the Command-Shell (speedy C:>) erfolgen.
too here was incidentally one "fester Ort" on the Werk: the Bootsektor-code loading The File IO.SYS and these thereafter MSDOS.SYS of a solid place: tappt im dunkeln mussten the two first File-Entries the Stammverzeichnisses his. moreover can tappt im dunkeln not fragmentiert his (d.h. any your Sektoren must directly one after another follow). this is necessary, because the "richtige" Dateisystem-driver (FAT32, NTFS or exFAT) first in the MSDOS.SYS-Analogon include is and the boat-code self yet plenty primitiver (machines-hither) To works goes.
the same counts incidentally too for others Installationen on Festplatte, and declared too The unbeweglichen Files, everybody can about in the Detailansicht of DEFRAG.EXE see can. furthermore ought to on this place too nachvollziehbar his, Why Bootmedien not simply therefore created go can, that one The notwendigen Files draufkopiert: tappt im dunkeln must to that a in a integrally designed place lying (- the went Perhaps yet by the copy in the right Order), to that others must the Bootsektor whom suitable code include. under MS-DOS Done the program SYS.COM very these steps.
summary
* an the first Betriebssystemdateien, The loaded becomes, is a Systemkonfigurationsdatei (for DOS in example The File CONFIG.SYS). Information in the Konfigurationsdatei help the loader at loading spezifischer Betriebssystemdateien, in example defined Gerätetreiber.
* an further File The loaded go must contains Information for specific Applications or command, The the user set has, so tappt im dunkeln nutzerspezifische pieces the boat-Prozesses started. In DOS becomes these File AUTOEXEC.BAT called. under windows dealt it itself thereby former around the File WIN.INI, nunmehr go Entries the Registry (the Systemdatenbank) worn out.
* after any Betriebssystemdateien loaded get, sustain the Betriebssystem self The Control the computers, lead anfängliche command through and wait on the first Benutzereingaben.
so far my Rückblick. but The Time is naturally not stehengeblieben... |
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| Computer: Gerät, daß es in Mikrosekunden erlaubt, 50.000 Fehler zu machen, zB 'daß' statt 'das'... | 06/20/21 ▲ |
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