Storage Stucture

• Main Memory--Computer data storage, often called storage or memory, refers to computer components, devices, and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers, and coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s.In contemporary usage, memory usually refers to a form of semiconductor storage known as random access memory (RAM) and sometimes other forms of fast but temporary storage. Similarly, storage today more commonly refers to mass storage - optical discs, forms of magnetic storage like hard disks, and other types slower than RAM, but of a more permanent nature. Historically, memory and storage were respectively called primary storage and secondary storage.




• Magnetic Disk-Magnetic Disk-Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads. As of 2009, magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals. In the field of computing, the term magnetic storage is preferred and in the field of audio and video production, the term magnetic recording is more commonly used. The distinction is less technical and more a matter of preference10.Storage Hierarchy-The hierarchical arrangement of storage in current computer architectures is called the memory hierarchy. It is designed to take advantage of memory locality in computer programs. Each level of the hierarchy has the properties of higher bandwidth, smaller size, and lower latency than lower levels.

• Moving Head Disk Mechanism-



• Magnetic Tapes-Magnetic tape is a medium for magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of plastic. Nearly all recording tape is of this type, whether used for recording audio or video or for computer data storage. It was originally developed in Germany, based on the concept of magnetic wire recording. Devices that record and playback audio and video using magnetic tape are generally called tape recorders and video tape recorders respectively. A device that stores computer data on magnetic tape can be called a tape drive, a tape unit, or a streamer.

Storage Hierarchy

• Caching-In computer science, a cache (pronounced /kæʃ/) is a collection of data duplicating original values stored elsewhere or computed earlier, where the original data is expensive to fetch (owing to longer access time) or to compute, compared to the cost of reading the cache. In other words, a cache is a temporary storage area where frequently accessed data can be stored for rapid access. Once the data is stored in the cache, it can be used in the future by accessing the cached copy rather than re-fetching or recomputing the original data.
  A cache has proven to be extremely effective in many areas of computing because access patterns in typical computer applications have locality of reference. There are several kinds of locality, but this article primarily deals with data that are accessed close together in time (temporal locality). The data might or might not be located physically close to each other (spatial locality).



• Coherency-In computing, cache coherence (also cache coherency) refers to the integrity of data stored in local caches of a shared resource. Cache coherence is a special case of memory coherence.
  When clients in a system maintain caches of a common memory resource, problems may arise with inconsistent data. This is particularly true of CPUs in a multiprocessing system. Referring to the "Multiple Caches of Shared Resource" figure, if the top client has a copy of a memory block from a previous read and the bottom client changes that memory block, the top client could be left with an invalid cache of memory without any notification of the change. Cache coherence is intended to manage such conflicts and maintain consistency between cache and memory.

• Consistency- in theory is one that does not contain a contradiction. The lack of contradiction can be defined in either semantic or syntactic terms. The semantic definition states that a theory is consistent if it has a model; this is the sense used in traditional Aristotelian logic, although in contemporary mathematical logic the term satisfiable is used instead. The syntactic definition states that a theory is consistent if there is no formula P such that both P and its negation are provable from the axioms of the theory under its associated deductive system.
  If these semantic and syntactic definitions are equivalent for a particular logic, the logic is complete. The completeness of sentential calculus was proved by Paul Bernays in 1918 and Emil Post in 1921, while the completeness of predicate calculus was proved by Kurt Gödel in 1930. Stronger logics, such as second-order logic, are not complete.

9.Magnetic Disk

-9.Magnetic Disk-Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads. As of 2009, magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals. In the field of computing, the term magnetic storage is preferred and in the field of audio and video production, the term magnetic recording is more commonly used. The distinction is less technical and more a matter of preference10.Storage Hierarchy-The hierarchical arrangement of storage in current computer architectures is called the memory hierarchy. It is designed to take advantage of memory locality in computer programs. Each level of the hierarchy has the properties of higher bandwidth, smaller size, and lower latency than lower levels.

8. Main Memory.

-Computer data storage, often called storage or memory, refers to computer components, devices, and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers, and coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s.
In contemporary usage, memory usually refers to a form of semiconductor storage known as random access memory (RAM) and sometimes other forms of fast but temporary storage. Similarly, storage today more commonly refers to mass storage - optical discs, forms of magnetic storage like hard disks, and other types slower than RAM, but of a more permanent nature. Historically, memory and storage were respectively called primary storage and secondary storage.

7.Difference of RAM and DRAM.

-Random-access memory (usually known by its acronym, RAM) is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order (i.e., at random). The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.[1]
By contrast, storage devices such as tapes, magnetic discs and optical discs rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than data transfer, and the retrieval time varies based on the physical location of the next item.
The word RAM is often associated with volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off. Many other types of memory are RAM, too, including most types of ROM and flash memory called NOR-Flash.





Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Since real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory.
The advantage of DRAM is its structural simplicity: only one transistor and a capacitor are required per bit, compared to four transistors in SRAM. This allows DRAM to reach very high density. Unlike Flash memory, it is volatile memory (cf. non-volatile memory), since it loses its data when the power supply is removed

6.Direct Memory Access.(DMA)

-Direct memory access (DMA) is a feature of modern computers and microprocessors that allows certain hardware subsystems within the computer to access system memory for reading and/or writing independently of the central processing unit. Many hardware systems use DMA including disk drive controllers, graphics cards, network cards and sound cards. DMA is also used for intra-chip data transfer in multi-core processors, especially in multiprocessor system-on-chips, where its processing element is equipped with a local memory (often called scratchpad memory) and DMA is used for transferring data between the local memory and the main memory. Computers that have DMA channels can transfer data to and from devices with much less CPU overhead than computers without a DMA channel. Similarly a processing element inside a multi-core processor can transfer data to and from its local memory without occupying its processor time and allowing computation and data transfer concurrency.

4.User Node.

-User-mode Linux (UML) enables multiple virtual Linux systems (known as guests) to run as an application within a normal Linux system (known as the host). As each guest is just a normal application running as a process in user space, this approach provides the user with a way of running multiple virtual Linux machines on a single piece of hardware, offering excellent security and safety without affecting the host environment's configuration or stability.

3.Monitor Mode.

-Monitor mode, or RFMON (Radio Frequency Monitor) mode, allows a computer with a wireless network interface card (NIC) to monitor all traffic received from the wireless network. Unlike promiscuous mode, which is also used for packet sniffing, monitor mode allows packets to be captured without having to associate with an access point or ad-hoc network first. Monitor mode only applies to wireless networks, while promiscuous mode can be used on both wired and wireless networks. Monitor mode is one of the six modes that 802.11 wireless cards can operate in: Master (acting as an access point), Managed (client, also known as station), Ad-hoc, Mesh, Repeater, and Monitor mode.

2. Difference of Interrupt and Trap and thier Use.

-In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution.
A hardware interrupt causes the processor to save its state of execution via a context switch, and begin execution of an interrupt handler.
Software interrupts are usually implemented as instructions in the instruction set, which cause a context switch to an interrupt handler similar to a hardware interrupt.
Interrupts are a commonly used technique for computer multitasking, especially in real-time computing. Such a system is said to be interrupt-driven.[1]

-In computing and operating systems, a trap is a type of synchronous interrupt typically caused by an exceptional condition (e.g. division by zero or invalid memory access) in a user process. A trap usually results in a switch to kernel mode, wherein the operating system performs some action before returning control to the originating process. In some usages, the term trap refers specifically to an interrupt intended to initiate a context switch to a monitor program or debugger.[1]

1. Bootstrap Program.

-1.bootstrap program-In computing, bootstrapping (from an old expression "to pull oneself up by one's bootstraps") is a technique by which a simple computer program activates a more complicated system of programs. In the start up process of a computer system, a small program such as BIOS, initializes and tests that hardware, peripherals and external memory devices are connected, then loads a program from one of them and passes control to it, thus allowing loading of larger programs, such as an operating system.

10. Storage hierarchy.

-10.Storage Hierarchy-The hierarchical arrangement of storage in current computer architectures is called the memory hierarchy. It is designed to take advantage of memory locality in computer programs. Each level of the hierarchy has the properties of higher bandwidth, smaller size, and lower latency than lower levels.
Most modern CPUs are so fast that for most program workloads, the locality of reference of memory accesses and the efficiency of the caching and memory transfer between different levels of the hierarchy are the practical limitation on processing speed. As a result, the CPU spends much of its time idling, waiting for memory I/O to complete. This is sometimes called the space cost, as a larger memory object is more likely to overflow a small/fast level and require use of a larger/slower level.

1. What is the difference of OS in terms of user's view and system's view?

-In user's view, Operating system is designed mostly for ease of use, with some attention to performance and none to resource utilization. While in system's view, operating system is serve as resource allocator.

2. Explain the Goals of Operating System?

-The Goals of OS is to give a pleasant and user interface, to give a satisfuction to the user, nice to operate, and conviniet to use.

3. What's the difference between Batch systems, Multiprogrammed systems, and Time-sharing systems?

-A batch system is one in which jobs are bundled together with the instructions necessary to allow them to be processed without intervention

As machines with more and more memory became available, it was possible to extend the idea of multiprogramming (or multiprocessing) as used in spooling batch systems to create systems that would load several jobs into memory at once and cycle through them in some order, working on each one for a specified period of time

The first involved timesharing or timeslicing. The idea of multiprogramming was extended to allow for multiple terminals to be connected to the computer, with each in-use terminal being associated with one or more jobs on the computer. The operating system is responsible for switching between the jobs, now often called processes, in such a way that favored user interaction. If the context-switches occurred quickly enough, the user had the impression that he or she had direct access to the computer.

4. Advanteges of Parallel systems.

-The advanteges of parallel system is, it has one or more processor and the other one is, if one processor is not functioning, there is a back up. because it has one or more processor.

5. Differentiate Symmetric Multiprocessing and Asymmetric Multiprocessing.

-symmetric multiprocessing or SMP involves a multiprocessor computer-architecture where two or more identical processors can connect to a single shared main memory
or example: the one is the Master and one is the slave. while the asymmetric processing is varies greatly from the standard processing model that we see in personal computers today. like there's no master or slave, fair.

6. Differentiate Client-server systems and Peer-to-Peer systems.

-The difference between the two is the client server is existing if there is a server and Client-server computing or networking is a distributed application architecture that partitions tasks or work loads between service providers (servers) and service requesters while the peer-to-preer server can be a client or server
at the same time.


Client-server systems.

Peer-to-peer systems.

7. Differentiate the Design issues of OS between a stand alone PC and a Workstation

-The Stand alone PC is just like your own PC, it doesn't connect with the other PC's,
while the Workstation connected PC is compose of one or two PC's but attached by two or more monitors.

8. Define the essential properties of the following types of OS.

a. Batch- are set up so they can be run to completion without human interaction, so all input data is preselected through scripts or command-line parameters. This is in contrast to "online" or interactive programs which prompt the user for such input. A program takes a set of data files as input, process the data, and produces a set of output data files. This operating environment is termed as "batch processing" because the input data are collected into batches on files and are processed in batches by the program.

b. Time Sharing- is sharing a computing resource among many users by multitasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major historical shift in the history of computing. By allowing a large number of users to interact simultaneously on a single computer, time-sharing dramatically lowered the cost of providing computing, while at the same time making the computing experience much more interactive

c. Real Time-In computer science, real-time computing (RTC) is the study of hardware and software systems that are subject to a "real-time constraint"—i.e., operational deadlines from event to system response. By contrast, a non-real-time system is one for which there is no deadline, even if fast response or high performance is desired or preferred. The needs of real-time software are often addressed in the context of real-time operating systems, and synchronous programming languages, which provide frameworks on which to build real-time application software

d. Network- networked systems consist of multiple computers that are networked together, usually with a common operating system and shared resources. Users, however, are aware of the different computers that make up the system.

e. Distributed-Distributed computing deals with hardware and software systems containing more than one processing element or storage element, concurrent processes, or multiple programs, running under a loosely or tightly controlled regime.


f. Handheld-Handheld is common names for mobile devices such as Hand-held camera,
Hand-held computer, Handheld computing ,Handheld (gaming),Handheld electronic game

IT-213 Operating Systems.

1. What is the difference of OS in terms of user's view and system's view?

-




2. Explain the Goals of Operating System?

-The Goals of OS is to give a pleasant and user interface, to give a satisfuction to the user, to have a

3. What's the difference between Batch systems, Multiprogrammed systems, and
Time-Sharing systems?
-

4. Advanteges of Parallel systems.

-The advanteges of parallel system is, it has one or more processor and the other one is, if one processor is not functioning, there is a back up. because it has one or more processor.

5. Differentiate Symmetric Multiprocessing and Asymmetric Multiprocessing.

-symmetric multiprocessing or SMP involves a multiprocessor computer-architecture where two or more identical processors can connect to a single shared main memory
or example: the one is the Master and one is the slave. while the asymmetric processing is varies greatly from the standard processing model that we see in personal computers today. like there's no master or slave, fair.

6. Differentiate Client-server systems and Peer-to-Peer systems.

-The difference between the two is the client server is existing if there is a server and Client-server computing or networking is a distributed application architecture that partitions tasks or work loads between service providers (servers) and service requesters while the peer-to-preer server can be a client or server
at the same time.

7. Differentiate the Design issues of OS between a stand alone PC and a Workstation
connected to a Network.
-The Stand alone PC is just like your own PC, it doesn't connect with the other PC's,
while the Workstation connected PC is compose of one or two PC's but attached by two or more monitors.

8. Define the essential properties of the following types of OS.

a. Batch- are set up so they can be run to completion without human interaction, so all input data is preselected through scripts or command-line parameters. This is in contrast to "online" or interactive programs which prompt the user for such input. A program takes a set of data files as input, process the data, and produces a set of output data files. This operating environment is termed as "batch processing" because the input data are collected into batches on files and are processed in batches by the program.

b. Time Sharing- is sharing a computing resource among many users by multitasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major historical shift in the history of computing. By allowing a large number of users to interact simultaneously on a single computer, time-sharing dramatically lowered the cost of providing computing, while at the same time making the computing experience much more interactive

c. Real Time-In computer science, real-time computing (RTC) is the study of hardware and software systems that are subject to a "real-time constraint"—i.e., operational deadlines from event to system response. By contrast, a non-real-time system is one for which there is no deadline, even if fast response or high performance is desired or preferred. The needs of real-time software are often addressed in the context of real-time operating systems, and synchronous programming languages, which provide frameworks on which to build real-time application software

d. Network-

e. Distributed-Distributed computing deals with hardware and software systems containing more than one processing element or storage element, concurrent processes, or multiple programs, running under a loosely or tightly controlled regime.


f. Handheld-Handheld is common names for mobile devices such as Hand-held camera,
Hand-held computer, Handheld computing ,Handheld (gaming),Handheld electronic game