1.)BOOTSTRAPT PROGRAM

Bootstrap program
In computing, booting is a bootstrapping process that starts operating systems when the user turns on a computer system.
Most computer systems can only execute code found in the memory (ROM or RAM); modern operating systems are mostly stored on hard disk drives, LiveCDs and USB flash drive. Just after a computer has been turned on, it doesn't have an operating system in memory. The computer's hardware alone cannot perform complicated actions of the operating system, such as loading a program from disk on its own; so a seemingly irresolvable paradox is created: to load the operating system into memory, one appears to need to have an operating system already installed.

2.)Difference of INTERRUPT and TRAP and their uses.

Trap is actually a software generated interrupt caused either by an error (for example division by zero, invalid memory access etc.), or by an specific request by an operating system service generated by a user program. Trap is sometimes called Exception. The hardware or software can generate these interrupts.

Interrupt or trap occurs, the hardware therefore, transfer control to the operating system which first preserves the current state of the system by saving the current CPU registers contents and program counter's value. after this, the focus shifts to the determination of which type of interrupt has occured. For each type of interrupt, separate segmants of code in the operating system determine what action should be taken and thus the system keeps on functioning by executing coputational instruction, I/O instruction, torage instruction etc.

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.

4.)USER MODE

USER MODE contains the userhelper program, which can be used to allow configured programs to be run with superuser privileges by ordinary users, and several graphical tools for users.

5.)DEVICE STATUS TABLE

DEVICE STATUS TABLE contains entry for each I/O deviceindicating its type, address, and state.

6.)Direct Memory Access

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.
Without DMA, using programmed input/output (PIO) mode for communication with peripheral devices, or load/store instructions in the case of multicore chips, the CPU is typically fully occupied for the entire duration of the read or write operation, and is thus unavailable to perform other work. With DMA, the CPU would initiate the transfer, do other operations while the transfer is in progress, and receive an interrupt from the DMA controller once the operation has been done. This is especially useful in real-time computing applications where not stalling behind concurrent operations is critical. Another and related application area is various forms of stream processing where it is essential to have data processing and transfer in parallel, in order to achieve sufficient throughput.

7.)Difference of RAM and DRAM

RAM (Random Access Memory) is a generic name for any sort of read/write memory that can be, well, randomly accessed. All computer memory functions as arrays of stored bits, "0" and "1", kept as some kind of electrical state. Some sorts support random access, others (such as the flash memory used in MP3 players and digital cameras) has a serial nature to it. A CPU normally runs through a short sequence of memory locations for instructions, then jumps to another routine, jumps around for data, etc. So CPUs depend on dynamic RAM for their primary memory, since there's little or no penalty for jumping all around in such memory. There are many different kinds of RAM.

DRAM is one such sort, Dynamic RAM. This refers to a sort of memory that stores data very efficiently, circuit-wise. A single transistor (an electronic switch) and a capacitor (charge storage device) store each "1" or "0". An alternate sort is called Static RAM, which usually has six transistors used to store each bit. The advantage of the DRAM is that each bit can be very small, physically. The disadvantage is that the stored charge doesn't last really long, so it has to be "refreshed" perodically. All modern DRAM types have on-board electronics that makes the refresh process pretty simple and efficient, but it is one additional bit of complexity. There are various sorts of DRAM around: plain (asynchronous) DRAM, SDRAM (synchronous, meaning all interactions are synchronized by a clock signal), DDR (double-data rate... data goes to/from the memory at twice the rate of the clock), etc. These differences are significant to hardware designers, but not usually a big worry for end-users... other than ensuring you buy the right kind of DRAM, if you plan to upgrade you system.


8.)MAIN MEMORY

Main memory
The main memory of the computer is also known as RAM, standing for Random Access Memory. It is constructed from integrated circuits and needs to have electrical power in order to maintain its information. When power is lost, the information is lost too! It can be directly accessed by the CPU. The access time to read or write any particular byte are independent of whereabouts in the memory that byte is, and currently is approximately 50 nanoseconds (a thousand millionth of a second). This is broadly comparable with the speed at which the CPU will need to access data. Main memory is expensive compared to external memory so it has limited capacity. The capacity available for a given price is increasing all the time. For example many home Personal Computers now have a capacity of 16 megabytes (million bytes), while 64 megabytes is commonplace on commercial workstations. The CPU will normally transfer data to and from the main memory in groups of two, four or eight bytes, even if the operation it is undertaking only requires a single byte.

9.)MAGNETIC DISK

Magnetic Disk
The primary computer storage device. Like tape, it is magnetically recorded and can be re-recorded over and over. Disks are rotating platters with a mechanical arm that moves a read/write head between the outer and inner edges of the platter's surface. It can take as long as one second to find a location on a floppy disk to as little as a couple of milliseconds on a fast hard disk.

10.)STORAGE HIERARCHY

Storage Hierarchy
The range of memory and storage devices within the computer system. The following list starts with the slowest devices and ends with the fastest. See storage and memory.
VERY SLOW
Punch cards (obsolete)
Punched paper tape (obsolete)
FASTER
Bubble memory
Floppy disks
MUCH FASTER
Magnetic tape
Optical discs (CD-ROM, DVD-ROM, MO, etc.)
Magnetic disks with movable heads
Magnetic disks with fixed heads (obsolete)
Low-speed bulk memory
FASTEST
Flash memory
Main memory
Cache memory
Microcode
Registers

COHERENCY AND CONSISTENCY

COHERENCY AND CONSISTENCY define the action of the processors to maintain coherence. More precisely, coherency defines what value is returned on a read, and consistency defines when it is available.


CACHING

The cache, a high-speed buffer establishing a storage hierarchy in the
Model 85, is discussed in depth in this part, since it represents the
bask organizational departure from other system/360 computers.
Discussed are organization and operation of the cache, including (he-
mechanisms used to locate and retrieve data needed by (he processor.
The internal performance studies that led to use of (he cache are de-
scribed, and simulated performance of the chosen configuration is
compared with that of a: theoretical system having an entire SO^nanq-
second main storage. Finally, the effects of varying cache parameters
are discussed and tabulated.