Computer terms we need to know

| Senin, 18 Juli 2011
There are several terms that we do not know about computers in advance about the structure of information systems on the computer itself, in this artikle I do not require you to read it but just providing an information that possibly you should know in this artikle.
The structure of a computer system can be divided into:• Computer Operating System.• The structure of I / O.• Storage Structure.• Storage Hierarchy.• Protection Hardware.Computer Operating SystemsToday multipurpose computer system comprises CPU (Central Processing Unit) and a number of devices connected through a bus controller that provides access to memory. Each device controller is responsible for managing a particular device (eg disk drives, audio devices, and video display). CPU and device controller can be run concurrently, however required synchronization mechanisms to regulate access to memory.At the first run or at boot time, there is an initial program that must be executed. This initial program called the bootstrap program. This program contains all aspects of computer systems, ranging from the CPU registers, device controllers, until the contents of memory.Interrupts are an important part of computer system architecture. Every computer system has a different mechanism. Interruptions can occur if the hardware (hardware) or software (software) get "served" by the processor. In the event of interruption of the processor to stop the process that was working, then switch in a service routine to service interruption. When finished working on service routine then the processor to resume a suspended process.The structure of I / OThis section will discuss the structure of the I / O, interrupt I / O, and DMA, as well as differences in interrupt handling.Interrupt I / OTo start the operation I / O, CPU loads the registers corresponding to the device controller. Instead device controller then examine the contents of the register to determine what operations should be done. At the time I / O operations run there are two possibilities, namely synchronous I / O and asynchronous I / O. In a synchronous I / O, control is returned to the user after the process I / O completed. While the asynchronous I / O, control is returned to the user without waiting for the I / O completion. So the process I / O and user processes can run simultaneously.DMA StructureDirect Memory Access (DMA) a method for handling I / O device controller which is directly related to memory without CPU intervention. Having set the buffers, pointers, and counters for the device I / O device controller transfers blocks of data directly to storage without the intervention of the CPU. DMA is used for I / O device with high speed. There is only one interrupt per block, in contrast to devices that have a low speed when an interrupt occurs for each byte (word).Storage StructureThe computer program must be in main memory (usually RAM) to be executed. The main memory is the only repository that can be directly accessed by the processor. Ideally the overall program and data can be stored in main memory permanently. However this is not possible because:• relatively small size of main memory to store data and programs as a whole.• Main memory is volatile, can not save it permanently, if the computer is turned off then the data stored in main memory will be lost.Main MemoryOnly main memory and registers are storage areas which can be accessed directly by the processor. Therefore, instructions and data to be executed must be stored in main memory or registers.For easier access I / O device to memory, computer architecture provides memory mapping facilities to the I / O. In this case the number of addresses in a memory mapped device registers. Read and write at this memory address causes the data transferred to and from the device registers. This method is suitable for devices with a fast response time as the video controller.Contained in the processor registers can be accessed within one clock cycle. This causes the register is a storage medium with the fastest access compared to main memory which requires a relatively long time. To overcome the speed difference, was made a buffer (buffer) storage is called a cache.Magnetic DiskMagnetic Disks act as secondary storage on a modern computer system. Magnetic disks are composed of discs such as CDs. The second disc surface covered by magnetic materials. The surface of the disk divided into tracks that play, which is then subdivided into several sectors.Storage HierarchyIn a storage hierarchy structure, the same data can appear in different levels of storage systems. For example, the integer A is located on the former B is added first, assuming the former B lies in the magnetic disk. The addition operation is processed by first removing I / O operations to duplicate a disk block on A which is located on the main memory operation is followed by the possibility penduplikatan A into the cache and penduplikatan A into the internal registers. So penduplikatan A occurs in several places. The first occurred in the internal registers where the value of A is different from that in the storage system. And the value in A will return the same when the new value is rewritten to a magnetic disk.On multi-processor conditions, the situation will become more complicated. This is because each processor has a local cache. Under these conditions the results of duplicates from A may only exist in some cache. Because the CPU (registers) can be run simultaneously, we must ensure that changes the value of A in one cache will change the value of A in all the existing cache. This is referred to as cache coherency.Hardware ProtectionPrevious computer systems programmer type-operated systems. When the computer is operated in the consuls they (users) must complete the system first. However, after the operating system was born then it was taken over by the operating system. For example on a monitor that process I / O has been taken over by the operating system, but once this is done by the user.To improve system utilization, the operating system will divide the system resources simultaneously throughout the program. Understanding spooling is a program can be done even if the I / O is still working on other processes and disk simultaneously using the data for many processes. Understanding multi-programming is an activity run multiple programs in memory at one time.This division was advantageous because many processes can run at one time but lead to new problems. When not in sharing it if something goes wrong will just make a program error. But if it is sharing in case of errors in one process / program will have an effect on other processes.So that the necessary protective (protection). Without protection if something goes wrong then just one program that can be run or the entire output of certain questionable.Many programming errors are detected by the hardware. This error is usually handled by the operating system. If an error occurs the program, the hardware will continue to the operating system and the operating system will interrupt and end it. Error messages delivered, and the memory of the program will be discarded. But the wasted memory is usually stored on disk so that the programmer can correct the error and run the program again.Dual Mode OperationTo ensure the operation goes well we should protect the operating system, programs, and data from the wrong programs. This protection requires shared resources. This can be done by the operating system provides hardware support that allows us to distinguish the mode of execution of the program.Mode we need two modes of operation namely:• Monitor Mode.• User Mode.In hardware there will be bits or bit mode which is useful to distinguish what mode is being used and what is being done. If it will be appreciating the Monitor Mode 0, and if the User Mode it will be worth 1.At boot time, the hardware works in monitor mode and after the operating system is loaded it will begin to go into user mode. When there is a trap or interrupt, the hardware will switch the state of the user mode again into monitor mode (change state into bits 0). And will return to user mode if the operating system takes over the process and computer control (state will turn into bits 1).Protection of I / OUsers can confuse the operating system to perform I / O instructions to access illegal memory locations for the operating system or by going to escape from the processor. To prevent this we consider all I / O instructions as instruction privileges so that they can not do the I / O instructions directly into memory but it should be through the operating system first. Protection of I / O is said complete if the user can be sure will not touch the monitor mode. If this is the case of protection of I / O can be compromised.Memory ProtectionOne is the protection of hardware memory protection is a limitation of memory usage. Here take a few terms are:• Base Register is beginning physical memory address of the allocated / may be used by the user.• Limit Register is the limit of physical memory address of the beginning of the allocated / may be used by the user.• Protection Hardware.For example, a user has a limited base register and have a limit registers 300 040 120 900 then the user is only allowed to use physical memory addresses between 300 040 to 420 940 only.Operating System StructureComponentsIn reality, not all operating systems have the same structure. However, according to Avi Silberschatz, Peter Galvin, and Greg Gagne, generally a modern operating system has the following components:• Process Management.• Main Memory Management.• Secondary-Storage Management.• Management System I / O.• File Management.• Protection System.• Network.• Command-Interpreter System.Management ProcessThe process is a state when a program is executed. A process requires some resources to accomplish its task. these resources can be CPU time, memory, files, and device-device I / O.The operating system is responsible for activities related to management processes such as:• Creation and removal of user processes and system processes.• Delaying or continue the process.• Providing mechanisms for process synchronization.• Providing mechanisms for process communication.• Provide a mechanism for handling deadlocks.Main Memory ManagementMain memory, or better known as the memory is a huge array of word or byte, the size in the hundreds, thousands or even millions. Each word or byte has its own address. Main memory serves as a repository of data access used by the CPU or a device I / O. The main memory includes a temporary data storage (volatile), meaning that data can be lost once the system is turned off.The operating system is responsible for activities related to memory management such as:• Keeping track of memory being used and who uses it.• Selecting a program that will be loaded into memory.• Allocate and to dealokasikan memory space as needed.Secondary-Storage ManagementThe data stored in main memory is temporary and the amount is very small. Therefore, to save the entire data and computer programs needed secondary-storage which is permanent and can accommodate a lot of data. Examples of secondary-storage is a hard drive, floppy, etc..Operating system is responsible for activities related to the disk-management such as: free-space management, storage allocation, disk scheduling.Management System I / OOften called the device manager. Provide a "device drivers" are common, so I / O operations can be uniform (open, read, write, close). Example: The user uses the same operation to read files on the hard-disk, CD-ROMs and floppy disks.Operating System components for the system I / O:• Buffer: hold temporary data from / to the device I / O.• Spooling: do the scheduling using I / O system to be more efficient (queues etc.)..• Provide drivers to be doing a "detailed" to the hardware I / O specific.File ManagementThe file is a collection of related information in accordance with manufacturer's destination file. The file may have a hierarchical structure (directories, volumes, etc..). Operating system is responsible for:• Creation and removal of the file.• Creation and removal of directories.• Supports manipulating files and directories.• Mapping files to secondary storage.• Backing up files to a permanent storage medium (non-volatile).System ProtectionProtection refers to the mechanism for controlling access by programs, processes, or users to the system resources. Protection mechanism must:• distinguish between the use of which has been given permission and that has not.• specify the controls to be imposed.• Provide a means of enforcement.NetworkA distributed system is a set of processors that do not share memory or clock. Each processor has its own memory. The processors are connected through a distributed network communication system provides user access to various system resources. Access to a:• Computation speed-up.• Increased data availability.• Enhanced reliability.Command-Interpreter SystemOperating System waiting for instruction from the user (command driven). Programs that read the instructions and interpreting control statements are generally known: control-card interpreter, command-line interpreter, and the UNIX shell. Command-Interpreter System varies from one operating system to another operating system and adapted to the purpose and the latest I / O devices that exist. For example: CLI, Windows, Pen-based (touch), and others.Operating System ServicesProgram execution is the system's ability to "load" the program into memory and run programs. I / O operations: the user can not directly access the hardware resources, operating systems must provide mechanisms to perform I / O on behalf of users. Dalah beam manipulation system ability to program in a file operation (read, write, create, and delete the file). Communication is the exchange of data / information between two or more processes that are on one computer (or more). Error detection is to maintain system stability by detecting the "error", like any hardware operation.Efesisensi use of the system:• Resource allocator is to allocate resources to multiple users or jobs that road at the same time.• Protection system ensures access to resources is controlled (user-controlled access to the system).• Accounting is the recording user activities, resource usage allotments (justice or wisdom).System CallsSystem call provides the interface between the program (user program running) and the OS. System call to be a bridge between the process and the operating system. System call is written in assembly language or high level language that can control the machine (C). Example: UNIX provides a system call: read, write => I / O operations to the file.Frequent user of the program must provide data (parameters) to the OS to be called. Example on UNIX: read (buffer, MAX_SIZE, file_id);Three ways to give the parameters of the program into the operating system:• Through the registers (CPU resources).• Store the parameters in the structure (table) in memory, and the table address pointer is stored in a register.• Push (store) the "stack" in memory and the OS picked it up through a pop on the stack page.Virtual MachinesA virtual machine (Virtual Machine) to use for example there is a system of programs => control programs that govern the use of hardware resources. Control program = trap system calls + access to the hardware. Control programs provide facilities to the user process. Getting the CPU and memory allocation. Provides interface "identical" to what is provided by the hardware => sharing devices for various processes.Virtual Machine (MV) (MV) => MV minimal control program that gives the illusion of multitasking: as if there is exclusive use processor and memory MV. MV sorting function and implementation of extended multitasking machine (depending on the user process) => flexible and easier to setup. If each user is assigned a single MV => free to run the OS (kernel) is desired on the MV. Potential of more than one OS in one computer. Example: IBM VM370: MV provides for various OS: CMS (interactive), MVS, CICS, etc.. Problem: Sharing disks => OS has a file system that may be different. IBM: the virtual disk (minidisk) is allocated to the user via the MV.MV concept provides complete protection for system resources, because each MV MV apart from the others. However, it caused no direct sharing of resources. MV is the right tool for research and development of operating systems. MV concept difficult to implement in connection with the effort required to provide a duplication of the main engines.System Design and ImplementationTarget for the user: the operating system must be convenient to use, easy to learn, reliable, secure and fast. Target system: the operating system must be easily designed, implemented, and maintained, as flexible, error, and efficient.Mechanisms and policies:• A mechanism to explain how to do something discretion to decide what to do. The separation of policy from mechanism is very important, this allows great flexibility when the policy will be changed later.• Policies to decide what to do.The separation of policy from mechanism is very important, this allows great flexibility when the policy will be changed later.System implementations typically use a cover assembly, the operating system can now be written using a high-level language. Code written in high level language: it can be made quickly, more concise, easier to understand and debug. Operating systems more easily transferred to other hardware if written in high level languages.System Generation (SYSGEN)Operating system designed to run on various types of machines; system must be configured for each computer. SYSGEN program to get information on the specific configuration of the system hardware.• Booting: start the computer by loading the kernel.• Bootstrap program: code that is stored in ROM code that can put the kernel, put it into memory and begin execution.SummaryOperating system has evolved over more than 40 years with two main objectives. First, the operating system trying to regulate the activities of computing to ensure a good utilization of the computing system. Second, providing a comfortable environment for the development and launch of the program.Initially, the computer system used from the front of the consul. Software such as assembler, loader, compiler linkerdan improve the convenience of programming the system, but also takes a lot of set-ups. To reduce set-up time, the used operator services and incorporates the same tasks (batch system). Batch system allows automatic sorting tasks by using the resident operating system and provides a significant increase in computer utilization. Computers no longer need to wait for operation by the user. But the CPU utilization is still low. This is because the slow speed of the tools for I / O relative to CPU speed. Off-line operation of the tools that slow aims to use some system-to-tape reader and tape-to-printer for a single CPU.To improve the overall capabilities of the computer system, the developers introduced the concept of multiprogramming. With multiprogramming, several tasks are stored in memory at a time; CPU are used interchangeably so that adds to CPU utilization and reduce the total time required to complete these tasks. Multiprogramming, which is designed to enhance the capability, also allows time-sharing. Operating systems that are time-shared to allow many users to use the computer interactively at the same time. Personal computer is a microcomputer which is considered smaller and less expensive than mainframe computers. Operating system for computers like these benefit from the development of operating systems for mainframe computers in several respects. However, since the use of computers for personal purposes, then the CPU utilization is no longer a major concern. Therefore, some designs for mainframe computers are not suitable for smaller systems.Parallel systems have more than one CPU that has a close relationship; those CPUs share a computer bus, and sometimes shared memory and other devices. Such a system can increase the throughput and reliabilititas. Hard real-time systems are often used as a controller for a dedicated application. Operating system is hard real-time has a fixed time limit that has been defined by baik.Pemrosesan must be completed within the constraints that have been defined, or the system will fail. Soft real-time system has fewer time constraints are hard, and do not support scheduling using the deadline. The influence of the Internet and World Wide Webbaru recently been encouraging the development of modern operating systems that include web browsers and other software and communications network as a whole.Multiprogramming and time-sharing systems improve the ability of computers to exceed the operating limits (overlap) CPU and I / O in one machine. Things like that require data transfer between CPU and I / O is handled either by polling or interrupt-driven access to the I / O port, or a DMA transfer. So that the computer can run a program, then the program must be in main memory (main memory). The main memory is the only place large storage that can be accessed directly by the processor, an array of word or byte, which has a size of hundreds of thousands to millions. Every word has its own address. The main memory is a volatile storage area, where the content is lost when the energy source (electrical energy) is turned off. Most computer systems provide secondary storage as an extension of main memory. The main requirement of the secondary storage is that it can store large amounts of data permanently. The most common secondary storage is a magnetic disk, that provides storage for programs want any data. Magnetic disks are nonvolatile data storage device that also provides random access. Magnetic tape is used primarily for backup, storage of information is rarely used, and as a medium of information transfer from one system to another.A variety of storage systems in a computer system can be arranged in a hierarchy based on speed and cost. The topmost level is the most expensive, but fast. The more down, perbit costs decrease, while increasing its access time (the slower). Operating system must ensure the correct operation of computer systems. To prevent users from running programs that disrupt the operation of the system, the hardware has two modes: user mode and monitor mode. Some commands (such as the command I / O and the halt command) is a special command, and can only be run in monitor mode. Memory must also be protected from modification by users. Timer to prevent repetition continuously (infinite loop). These things (dual mode, special commands, the security memory, timer interrupt) is the basic building blocks used by the operating system to achieve the appropriate operation.The operating system provides many services. At the lowest level, system calls, allowing running programs to make requests directly from the operating system. At the highest level, the command interpreter or shell provides a mechanism for users to make requests without writing programs. Command can emerge from the former when running batch-mode, or directly from the terminal when the mode or time-shared interaktive. Program systems provided to meet most of user requests. Type of demand varies according to level. Level system call should provide the basic functions, such as process control and manipulation of tools and accessories. Request with a higher level (the command interpreter or program the system) is translated into a sequence of system calls.Service system can be grouped into several categories: program control, status requests and requests I / O. Program errors can be considered as an implicit request for service. When the service system is defined, then the structure of the operating system can be developed. A variety of tables needed to store information that defines the status of the computer system and the status of the task system. The design of a new operating system is a major task. It is essential that the objectives of the system has been well defined before starting the design. The desired type of system is the basis in selecting a variety of algorithms and strategies that will be used. Because the magnitude of the operating system, then the modularity is important. Designing the system as a sequence of layers or by using a microkernel is one good technique. The concept of a virtual machine takes the approach that treats both the layer and the kernel of the operating system and hardware as a hardware. Even other operating systems can be included on the virtual machine. Any operating system that implements the JVM can run any Java program, because the underlying JVM of the system to the Java program, providing a neutral view of architecture.In the operating system design cycle, we must be careful to separate the division policy (policy decision) with the details of implementation (mechanism). This separation makes the maximum flexibility if policy decision will be changed later. Operating system is now almost always written using high level languages. This increases the implementation, maintenance portability. To make the operating system for a particular engine configuration, we have to do a system generation.A computer system consists of five basic structural units, namely:• The unit input (Input Unit)• The control unit (Control Unit)• arithmetic and logic unit (Arithmetic & Logical Unit / ALU)• Unit memory / storage (Memory / Storage Unit)• The unit outputs (Output Unit)Control Unit and ALU form a separate unit called the Central Processing Unit (CPU). The relationship between each of the units that make up a computer system can be seen in the figure below:
Data received via the Input Device and sent to the Memory. In the Memory data is stored and subsequently processed in the ALU. The results are stored back to memory the process prior to release via the Output Device. Control and coordination of the system is performed by the Control Unit. In summary the working principle of the computer is Input - Process - Output, known by the acronym IPO.Main functions of each unit will be explained below:• Input Unit (Input Unit)Serves to receive input (input) and then read and forwarded to the Memory / storage. In this connection, the technical term input device (input device) that is the receiver and reader input and the input media is the intermediary.• Control Unit (Control Unit)Serves to carry out supervision and control of the entire computer system. He serves as regulator of the household computer, decide the order of operations for the entire system, generating and controlling signals to control operations and adjust the flow of data from the address bus (address bus) and data bus (data bus), and to control and interpret the signals -control signals on control bus (control bus) of a computer system. Understanding of the bus can be seen at the bottom of this page.• Logic & Arithmetic Unit (Arithmetical & Logical Unit)Serves to carry out the work or arithmetic & logic calculations such as add, subtract, multiply, divide and constituent. It is also carrying out work such as data transfer, pooling of data, election data, compare data, etc., so that the ALU is a core part of a computer system. On some computer systems and help to lighten the task of the ALU of the CPU is given an additional device called a coprocessor so that in particular the process of calculation and execution of work in general to be faster. Understanding of the coprocessor can be found at the bottom of this page.• Unit Memory / Storage (Memory / Storage unit)Serves to accommodate the data / programs received from units of input before processing by the CPU and also receive data when processed by the CPU which then forwarded to the output unit. In a computer system there are two kinds of memory, that naming depends on whether the device can only read or can read and write to him. Part of memory that can only be read without being able to write to her so-called ROM (Read Only Memory), while the memory can perform read and write is called RAM (Random Access Memory).• Unit Output (Output Unit)Serves to receive the results of data processing from the CPU through the memory. As with the input unit to output unit is also known term output devices (output device) and output media (output media).________________________________________
Understanding BUSThe bus is a group of signal path used to move bits of information from one place to another, grouped according to Standard functions of a computer system bus is the address bus (address bus), data bus (data bus) and the control bus (control bus) .

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