X86-Virtualisierung bezeichnet hardware- und softwarebasierte Mechanismen zur Unterstützung der Virtualisierung für Prozessoren, die auf der x86-Architektur basieren.
Operating Systemsa history and introduction. This part of THOCP has. That someone needs to have a general grasp on what an OS. In the meantime. all suggestions from our readers concerning OS's are put here as we are.
So this section. is really under construction, any suggestion or information is welcome. An OS takes care for all input and output in a computer system.
It manages. users, processes, memory management, printing, telecommunication, networking. It sends data to a disk, the printer, the screen and other peripherals connected. And because every machine is build different, commands for in or output will.
In almost all cases an Operating System. OS. Because of the compactness of these small supporting. OS than to redesign. In general programmers only have to make a . As well as that programs can run on different types of machines with. CPU's without changing anything in the program. This is what. makes a standard Operating System so important.
In fact any form of standardization is important for production and compatibility. Functions and Structure. Introduction At first operating systems were designed to help applications interact with. While this is still the case, the importance of the operating.
Most users engaged in the Mac - PC - Unix. The operating system provides a layer of abstraction between the user and the. Users and applications do not see the hardware directly, but view. This abstraction can be used to hide certain hardware details from users and.
Thus, changes in the hardware are not seen by the user (even though. OS must accommodate them). This is particularly advantageous for venders that want offer a consistent.
OS interface across an entire line of hardware platforms. For example, certain. D graphics hardware can be controlled by. When an instruction pertaining to the hardware is executed. However, if the hardware is. In this case. the OS can emulate the desired instruction in software. Another way that abstraction can be used is to make related devices appear.
For example, hard disks, floppy disks. CD- ROMs, and even tape are all very different media, but in many operating systems. Unix, and increasingly Windows NT, take this abstraction even further. From. a user and application programmer standpoint, Unix is Unix regardless of the. CPU make and model. As previously mentioned, it is this feature of Unix more. Unix's popularity.
We can view an operating system as providing four basic interfaces: interface to the underlying hardware interface to application programs interface to the user interface to the system manager. Each of these interfaces provides the appropriate view for different groups. OS- hardware interface. Many books that purport. Most operating systems in use today are composed of two distinct parts: the. The kernel is primarily responsible for the.
Functionality of the Operating System Kernel. Processes. A key abstraction utilized in the design of an operating system is the notion. A process is a program in execution. The kernel is. responsible for creating, scheduling and deleting processes and often for inter- process.
Resource Allocation. Modern operating systems often provide users and applications with a virtual. CPU. Whether the computer has one CPU or several CPUs, it is usually the case that. CPUs. Thus, the operating system is responsible. CPU(s). Memory. There is a finite amount of memory that must be shared among the processes. Note that this is a different.
IO is being performed for processes. Some devices (e. g. The operating system is responsible for managing and protecting. Support Services. Another important operating system task is providing support. These include: Support for IO operations.
We've already discussed how the operating system. IO to enforce a protection scheme.
File system management. Networking. Protection. Interrupts and Traps.
A great deal of the kernel consists of code that is. While the words . An interrupt is a CPU event that is triggered by some external device.
A trap is a CPU event that is triggered by a program. Traps are sometimes. They can be deliberately triggered by a special. When an interrupt is triggered by an external device the hardware will save. This routine is a first level interrupt handler.
It can either service the. When the handler finishes it usually causes the CPU to resume the processes.
However, the operating system may schedule another process. When an executing process requests a service from the kernel using a trap. CPU is placed in kernel mode, and. This kernel code is called the system service dispatcher. It examines parameters. CPU registers. to determine what action is required.
Control then passes to the code that performs. When the service is finished, control is returned to either the process that. Traps can also be triggered by a fault. In this case the usual action is to. It is possible on some systems for applications.
Operating System Design Principles Operating system design is a complex task. One of the driving forces behind. OS design. System design goals: User interface: should the interface be easy to learn by a novice user, or. Unfortunately, the more complete the. Once again, the more secure a system is the less efficient it is. Flexibility. Most operating systems come preconfigured for many different. Part of the process of setting up a particular machine is to construct.
It also involves specifying the attached hardware so that only. Some operating systems can load and unload. Portability. Will the operating system be portable to widely varying types. Backwards compatibility and emulation. Is it important that software that.
Layered design: Operating system consists of multiple layers. Each layer depends on the on. Advantages: improved security, since only layers close to hardware need to operate. Disadvantages: deciding what functionality to put in each layer can be difficult. This. is because there are some interdependencies that would violate the layering.
Distinction between mechanisms and policies: a mechanism is a facility the system provides the system manager. For example. VMS allows the manager to control whether or not a given account can be logged. For example, a company may decide that it will not allow privileged accounts. In a typical multi- user system, users are expected to know that the machine. In virtual machine operating systems an addition layer of abstraction is placed. Usually it is the case that a more powerful machine is used to host several. For example, the 8.
Intel CPUs supported virtual. Thus, an operating system designed for the 8.
MS- DOS and appear to the user to be several different. PCs at the same time. Another example of a virtual machine system is the IBM 3.
VM. operating system. This allowed users to work as if they had a dedicated (but. Stacked Job Batch Systems (mid 1.
A batch system is one in which jobs are bundled together with the instructions. The basic physical layout of the memory of a batch job computer is shown below: Monitor (permanently resident) User Space(compilers, programs, data, etc.) The monitor is system software that is responsible for interpreting and carrying. When the monitor starts a job, the entire. A sample of several batch jobs might look like this: $JOB user.
Advantages of batch systemsmove much of the work of the operator to the computerincreased performance since it was possible for job to start as soon as. Disadvantagesturn- around time can be large from user standpointmore difficult to debug programdue to lack of protection scheme, one batch job can affect pending jobs. One of the major shortcomings of early batch systems is that there's no protection. The solution to this brought a simple protection scheme, where certain memory.
To keep user programs from reading too many (or not enough) cards, the hardware. IO can only be performed in monitor mode. IO requests from the user programs are passed to the monitor.
In this. way, the monitor can keep a job from reading past it's on $EOJ card. To prevent an infinite loop, a timer is added to the system and the $JOB card. This means. that the CPU is idle (or nearly so) during these relatively slow operations. Since it is faster to read from a magnetic tape than from a deck of cards.
The smaller computers were used to read. The output from the jobs would be written to another tape which would.
It was a logical extension of the timer idea described above to have a timer. IO operation. Since the IO operation could proceed. CPU was crunching on a user program, little degradation in performance. Since the computer can now perform IO in parallel with computation, it became.
This process is called. SPOOLing: Simultaneous Peripheral Operation On. Line. Spooling batch systems were the first and are the simplest of the multiprogramming. One advantage of spooling batch systems was that the output from jobs was available. Multiprogramming Systems (1. As machines with more and more memory became available, it was possible to. Monitor (more like an operating system) User program 1.
User program 2. User porgram 3. User program 4. At this point the monitor is growing to the point where it begins to resemble. It is responsible for: * starting user jobs* spooling operations* IO for user jobs* switching between user jobs* ensuring proper protection while doing the above As a simple, yet common example, consider a machine that can run two jobs at. Further, suppose that one job is IO intensive and that the other is CPU.
One way for the monitor to allocate CPU time between these jobs would. However, the CPU would be idle much. IO bound process was executing. A good solution in this case is to allow the CPU bound process (the background. IO bound process (the foreground job) needs some CPU.
Presumably it will soon. IO and the monitor can return the CPU to the background job. Timesharing Systems (1.
Back in the days of the . As hardware. and software was developed to create monitors, simple and spooling batch systems. Users, and programmers in particular, longed to be able to . In the 1. 97. 0s and. The first involved timesharing or timeslicing.
Intel 8. 08. 6 microprocessor architecture Memory. Program, data and stack memories occupy the same memory space. As the most of the processor. KB of memory. To access memory outside of 6. KB the CPU uses. special segment registers to specify where the code, stack and data 6. KB. segments are positioned within 1 MB of memory (see the .
Accessing. data from the Data, Code, Stack or Extra segments can be usually done by prefixing. DS: , CS: , SS: or ES: (some registers and instructions. ES or SS segments instead of DS segment). Reading word data from even byte boundaries requires only. Each interrupt vector.
FFFF0h - FFFFFh - after RESET the processor always starts program execution. FFFF0h address. Interrupts. The processor has the following interrupts. INTR is a maskable hardware interrupt. When an interrupt occurs, the processor. FLAGS register into stack, disables further interrupts.
Interrupt processing routine should. IRET instruction. Interrupt is processed in the same way as.
INTR interrupt. Interrupt type of the NMI is 2, i. This is a type 3 interrupt. INT < interrupt number> instruction - any one interrupt from available 2. INTO instruction - interrupt on overflow Single- step interrupt - generated if the TF flag is set. This is a type 1 interrupt.
Processor exceptions: divide error (type 0), unused opcode (type 6) and. Software interrupt processing is the same as for the hardware interrupts.
I/O ports. 65. 53. I/O ports. Registers. Most of the registers contain data/instruction offsets within 6. KB memory segment. To specify where in 1 MB of processor memory these 4 segments. Code segment (CS) is a 1. KB segment. with processor instructions.
The CS register is. The general registers are. Accumulator register consists of 2 8- bit registers AL and AH, which can be. AX. AL in this case. AH contains the high- order byte. BL in this case. contains the low- order byte of the word, and BH contains the high- order byte.
When combined. CL register contains the low- order byte of the word. CH contains the high- order byte. When combined. DL register contains the low- order byte of the word. DH contains the high- order byte. Direction Flag (DF) - if set then string manipulation instructions will. Tag The Power Of Paint 2009 Pc Game. If cleared then the index registers.
Interrupt- enable Flag (IF) - setting this bit enables maskable interrupts. Single- step Flag (TF) - if set then single- step interrupt will occur after. Sign Flag (SF) - set if the most significant bit of the result is set. Zero Flag (ZF) - set if the result is zero.
Auxiliary carry Flag (AF) - set if there was a carry from or borrow to. AL register. Parity Flag (PF) - set if parity (the number of . Carry Flag (CF) - set if there was a carry from or borrow to the most.
Instruction Set. Instruction set of Intel 8. Data moving instructions. Arithmetic - add, subtract, increment, decrement, convert byte/word and compare. Logic - AND, OR, exclusive OR, shift/rotate and test.
String manipulation - load, store, move, compare and scan for byte/word. Control transfer - conditional, unconditional, call subroutine and. Input/Output instructions. Other - setting/clearing flag bits, stack operations, software interrupts, etc. Addressing modes. Implied - the data value/data address is implicitly associated with the instruction. This addressing mode works with SI, DI.
BX and BP registers.