Final Terms1

8/3/2019 Final Terms1

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(1) Flip-flop

In digital circuits, a flip-flop is a term referring to an electronic circuit that has two stable states and

thereby is capable of serving as one bit ofmemory.A flip-flop is usually controlled by one or two

control signals and/or a gate orclock signal. The output often includes the complement as well as the

normal output.

Uses :-

A single flip-flop can be used to store onebit, or binary digit, of data.

Any one of the flip-flop type can be used to build any of the others.

Many logic synthesis tools will not use any other type than D flip-flop and D latch.

Level sensitive latches cause problems with Static Timing Analysis (STA) tools and Design

For Test (DFT). Therefore, their usage is often discouraged. Many FPGA devices contain only edge-triggered D flip-flops

(2) Adder

In electronics, an adder orsummer is a digital circuit that performs addition of numbers. In modern

computers adders reside in the arithmetic logic unit (ALU) where other operations are performed.

Although adders can be constructed for many numerical representations, such as Binary-coded

decimal or excess-3, the most common adders operate on binary numbers. In cases where two's

complement orone's complement is being used to represent negative numbers, it is trivial to modify

an adder into an adder-subtractor. Other signed number representations require a more complex

adder.

Types:-

(a) Half adder

A half adder is a logical

circuit that performs an

addition operation on two one-bit binary numbers often written asA andB. The half adder output isa sum of the two inputs usually represented with the signals Coutand Swhere

.

Example half adder circuit diagramAs an example, a Half Adder can be built with an XOR gateand an AND gate.

___________

A ------| |

| Half |-----

| Adder || |-----

B ------|___________|

1

Inputs Outputs

A B C S 0 0 0 0

0 1 0 1

1 0 0 1

1 1 1 0
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(b) Full adder

Schematic symbol for a 1-bit full

adder with Cin and Cout drawn on

sides of block to emphasize their

use in a multi-bit adder.

A full adder is a logical circuit

that performs an addition operation on three one-bit binary numbers often written as A, B, and Cin.The full adder produces a two-bit output sum typically represented with the signals Cout and Swhere

.

(3) Subtractor

In electronics, a subtractor can be designed using the same approach as that of an adder. The binary

subtraction process is summarized below. As with an adder, in the general case of calculations on

multi-bit numbers, three bits are involved in performing the subtraction for each bit of the difference:

the minuend (Xi), subtrahend (Yi), and a borrow in from the previous (less significant) bit order

position (Bi). The outputs are the difference bit (Di) and borrow bitBi + 1.

K-mapBi(1,2,3,7)

Subtractors are usually implemented within a binary adder for only a small cost when using the

standard two's complement notation, by providing an addition/subtraction selector to the carry-in and

to invert the second operand.

(definition of two's complement negation)

2

Inputs Outputs

A B C iCo S0 0 0 0 0

1 0 0 0 10 1 0 0 1

1 1 0 1 0

0 0 1 0 1

1 0 1 1 0

0 1 1 1 0

1 1 1 1 1
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(a) Half Subtractor

The half-subtractor is a combinational

circuit which is used to perform

subtraction of two bits. It has two inputs,

X (minuend) and Y (subtrahend) and two

outputs D (difference) and B (borrow).

From the above table one can draw the

Karnaugh map for "difference" and

"borrow".

So, Logic equations are:

(b) Full Subtractor

The Full_subtractor is a combinational circuit which is used to perform subtraction of threebits. It

has three inputs, X (minuend) and Y (subtrahend) and Z (subtrahend) and two outputs D (difference)

and B (borrow).

Easy way to write truth table

D=X-Y-Z (don't bother about sign)

B = 1 If X


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(4) Opcode

In computer technology, an opcode (operation code) is the portion of a machine languageinstruction that specifies the operation to be performed. Their specification and format are laid out in

the instruction set architecture of the processor in question (which may be a general CPU or a more

specialized processing unit). Apart from the opcode itself, an instruction normally also has one or

more specifiers foroperands (i.e. data) on which the operation should act, although some operations

may have implicitoperands, or none at all. There are instruction sets with nearly uniform fields foropcode and operand specifiers, as well as others (the x86 architecture for instance) with a more

complicated, varied length structure. Depending on architecture, the operands may be register

values, values in the stack, othermemory values, I/O ports, etc, specified and accessed using more or

less complex addressing modes. The types ofoperations include arithmetics, data copying, logical

operations, and program control, as well as special instructions (such as CPUID and others).

(5) Instruction Code

In digital computers, a set of instructions that assigns algorithms for solving problems in a digital

computer; the principal part of the machine language. Problem-solving programs are compiled

according to definite rules with the aid of an instruction code. An instruction code is usually

presented in the form of tables that give mnemonic designations of the instructions according to their

structure, as well as declarations of format, restrictions on usage, and all the computer operations

controlled by the instructions.

An instruction code is not the same as an operations system. Two computers that have the same

operations systems may differ in their instruction codesfor example, in their instruction address or

instruction content (the complex of operations that are combined by each operation code). The

efficiency in solving different problems depends to a considerable extent on the instruction codes

capability of producing the necessary algorithms. Consequently, this is one of the fundamental

parameters determining the structure of a digital computer. An instruction code is selected by

simulation of the structural scheme of the planned computer, by experimental programming using the

chosen code, and by evaluation and comparison of the results. In general-purpose digital computers

of low and medium capacity, the number of different operations in the instruction code varies from

32 to 64, and in high-performance computers it is in the range of 100 or more.

In modern digital computers the instruction code can be replaced or reorganized within certain limits

by using micro programmed control and extended by connecting to the computer additional

hardware, needed, for example, to process data in decimal notation when solving problems in

economics.

An instruction code is an intermediate step between the programmers language and the computers

performance in executing a problem-solving program. Therefore, the program for the solution is

executed in two stages: translation into the instruction language and conversion of the instructions

into a control sequence of signals. The two-stage process simplifies the structure of the computer.

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(6) Reduced Instruction Set Computing

Reduced instruction set computing, orRISC (pronounced / r sk/ ), is a CPU design strategy based

on the insight that simplified (as opposed to complex) instructions can provide higher performance if

this simplicity enables much faster execution of each instruction. A computer based on this strategy

is a reduced instruction set computer (also RISC). There are many proposals for precise

definitions[1], but the term is slowly being replaced by the more descriptive load-store architecture.

Well known RISC families include DEC Alpha, AMD 29k, ARC, ARM, Atmel AVR, MIPS, PA-

RISC, Power(including PowerPC), SuperH, and SPARC.

Some aspects attributed to the first RISC-labeleddesigns around 1975 include the observations thatthe memory-restricted compilers of the time were often unable to take advantage of features intended

to facilitate manual assembly coding, and that complex addressing modes take many cycles toperform due to the required additional memory accesses. It was argued that such functions would be

better performed by sequences of simpler instructions if this could yield implementations small

enough to leave room for many registers,[2] reducing the number of slow memory accesses. In these

simple designs, most instructions are of uniform length and similar structure, arithmetic operations

are restricted to CPU registers and only separate loadand store instructions access memory. These properties enable a better balancing of pipeline stages than before, making RISC pipelines

significantly more efficient and allowing higherclock frequencies.

(7) Associative Memory

Associative memory (content-addressable memory, CAM) A memory that is capable of

determining whether a given datum the search word is contained in one of its addresses orlocations. This may be accomplished by a number of mechanisms. In some cases parallel

combinational logic is applied at each word in the memory and a test is made simultaneously for

coincidence with the search word. In other cases the search word and all of the words in the memory

are shifted serially in synchronism; a single bit of the search word is then compared to the same bit

of all of the memory words using as many single-bit coincidence circuits as there are words in the

memory. Amplifications of the associative memory technique allow for masking the search word or

requiring only a close match as opposed to an exact match. Small parallel associative memories are

used in cache memory and virtual memory mapping applications.

Since parallel operations on many words are expensive (in hardware), a variety of stratagems are

used to approximate associative memory operation without actually carrying out the full test

described here. One of these uses hashing to generate a best guess for a conventional address

followed by a test of the contents of that address.

a storage unit of digital computers in which selection (entry) is performed not according to concreteaddress but rather according to a preset combination (association) of attributes characteristic of the

desired information. Such attributes can be part of a word (number), attached to it for detection

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among other words, certain features of the word itself (for example, the presence of specific codes in

its digits), the absolute value of a word, its presence in a preset range, and so on.

The operation of an associative memory is based on the representation of all information in the form

of a sequence of zones according to properties and characteristic attributes. In this case the retrieval

of information is reduced to the determination of the zone according to the preset attributes by meansof scanning and comparison of those attributes with the attributes that are stored in the associative

memory. There are two basic methods of realizing the associative memory. The first is the

construction of a memory with storage cells that have the capability of performing simultaneously

the functions of storage, nondestructive reading, and comparison. Such a method of realizing an

associative memory is called network parallel-associativethat is, the required sets of attributes are

preserved in all the memory cells, and the information that possesses a given set of attributes is

searched for simultaneously and independently over the entire storage capacity. Card indexes for

edge-punched cards are prototypes of such an associative memory. Thin-film kryotrons, transfluxors,

biaxes, magnetic thin films, and so on are used as storage elements of network-realized associative

memories.

The second method of realizing an associative memory is the programmed organization (modeling)

of the memory. It consists of the establishment of associative connections between the information

contained in the memory by means of ordered arrangement of the information in the form of

sequential chains or groups (lists) connected by linkage addresses whose codes are stored in the same

memory cells. This procedure is the more suitable for practical realization in dealing with large

volumes of information because it provides for the use of conventional accumulators with address

reference.

The use of an associative memory considerably facilitates the programming and solution of

informational-logical problems and accelerates by hundreds (thousands) of times the speed of

retrieval, analysis, classification, and processing of data.

(8) 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 isespecially useful in real-time computing applications where not stalling behind concurrent operations

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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.

Principle

DMA is an essential feature of all modern computers, as it allows devices to transfer data without

subjecting the CPU to a heavy overhead. Otherwise, the CPU would have to copy each piece of data

from the source to the destination, making itself unavailable for other tasks. This situation is

aggravated because access to I/O devices over a peripheral bus is generally slower than normal

system RAM. With DMA, the CPU gets freed from this overhead and can do useful tasks during data

transfer (though the CPU bus would be partly blocked by DMA). In the same way, a DMA engine in

an embedded processor allows its processing element to issue a data transfer and carries on its own

task while the data transfer is being performed.

A DMA transfer copies a block of memory from one device to another. While the CPU initiates the

transfer by issuing a DMA command, it does not execute it. For so-called "third party" DMA, as is

normally used with the ISAbus, the transfer is performed by a DMA controller which is typically

part of the motherboard chipset. More advanced bus designs such as PCI typically usebus mastering

DMA, where the device takes control of the bus and performs the transfer itself. In an embedded

processorormultiprocessor system-on-chip, it is a DMA engine connected to the on-chip bus that

actually administers the transfer of the data, in coordination with the flow control mechanisms of the

on-chip bus.

A typical usage of DMA is copying a block of memory from system RAM to or from a buffer on the

device. Such an operation usually does not stall the processor, which as a result can be scheduled to

perform other tasks unless those tasks include a read from or write to memory. DMA is essential to

high performance embedded systems. It is also essential in providing so-called zero-copy

implementations of peripheral device drivers as well as functionalities such as network packet

routing, audio playback and streaming video. Multicore embedded processors (in the form of

multiprocessor system-on-chip) often use one or more DMA engines in combination with scratchpad

memories for both increased efficiency and lower power consumption. In computer clusters forhigh-

performance computing, DMA among multiple computing nodes is often used under the name of

remote DMA. There are two control signal used to request and acknowledge a DMA transfer in

microprocess-based system.The HOLD pin is used to request a DMA action and the HLDA pin is anoutput acknowledges the DMA action.

A coprocessor is a computerprocessor used to supplement the functions of the primary processor

(the CPU). Operations performed by the coprocessor may be floating point arithmetic, graphics,

signal processing, string processing, orencryption. By offloading processor-intensive tasks from the

main processor, coprocessors can accelerate system performance. Coprocessors allow a line of

computers to be customized, so that customers who do not need the extra performance need not pay

for it.

(9) Coprocessors

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Coprocessors were first seen on mainframe computers, where they added "optional" functionality

such as floating point math support. A more common use was to control input/output channels,

where they were more often called channel controllers.

Intel coprocessors

i8087 and i80287 microarchitecture.

i80387 microarchitecture.

The original IBM PC included a socket for the Intel 8087 floating-point coprocessor (aka FPU)

which was a popular option for people using the PC for CAD or mathematics-intensive calculations.

In that architecture, the coprocessor sped up floating-point arithmetic on the order of fiftyfold. Users

that only used the PC for word processing, for example, saved the high cost of the coprocessor,

which would not have accelerated performance of text manipulation operations.

The 8087 was tightly integrated with the 8086/8088 and responded to floating-point machine code

operation codes inserted in the 8088 instruction stream. An 8088 processor without an 8087 would

interpret these instructions as an internal interrupt, which could be directed to trap an error or to

triggeremulation of the 8087 instructions in software.

Intel 80386 CPU w/ 80387 Math Coprocessor

Another coprocessor for the 8086/8088 central processor was the 8089 input/output coprocessor. Itused the same programming technique as 8087 for input/output operations, such as transfer of data

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from memory to a peripheral device, and so reducing the load on the CPU. But IBM didn't use it in

IBM PC design and Intel stopped development of this type of coprocessor.

During the era of 8- and 16-bit desktop computers another common source of floating-point

coprocessors was Weitek. The Intel 80386 microprocessorused an optional "math" coprocessor (the

80387) to perform floating point operations directly in hardware.

The Intel 80486DX processor included floating-point hardware on the chip. Intel released a cost-

reduced processor, the 80486SX, that had no FP hardware, and also sold an 80487SX co-processor

that essentially disabled the main processor when installed, since the 80487SX was a complete

80486DX with a different set of pin connections.

Intel processors later than the 80486 integrated floating-point hardware on the main processor chip;

the advances in integration eliminated the cost advantage of selling the floating point processor as an

optional element. It would be very difficult to adapt circuit-board techniques adequate at 75 MHz

processor speed to meet the time-delay, power consumption, and radio-frequency interference

standards required at gigahertz-range clock speeds. These on-chip floating point processors are stillreferred to as coprocessors because they operate in parallel with the main CPU.

Motorola coprocessors

The Motorola 68000 family had the 68881/68882 coprocessors which provided similar floating-point

speed acceleration as for the Intel processors. Computers using the 68000 family but not equipped

with the hardware floating point processor could trap and emulate the floating-point instructions in

software, which, although slower, allowed one binary version of the program to be distributed forboth cases

(10) Universal set

For "universal set" in the sense of a universe of discourse with respect to which

the absolute set complement is taken.

In set theory, a universal set is a set which contains all objects, including itself.[1] In set theory as

usually formulated, the conception of a set of all sets leads to aparadox. The reason for this lies with

the parameters of Zermelo's axiom of separation: for any formula and set A, the set

which contains exactly those elements x ofA that satisfy exists. If the

universal set Vexisted, then Russell's paradox could be resolved by considering

. More generally, for any setA we can prove that is not an element ofA.

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A second issue is that the power set of the set of all sets would be a subset of the set of all sets,

providing that both exist. This conflicts with Cantor's theorem that the power set of any set (whether

infinite or not) always has strictly highercardinality than the set itself.

The idea of a universal set seems intuitively desirable in the ZermeloFraenkel set theory,

particularly because most versions of this theory do allow the use of quantifiers over all sets (seeuniversal quantifier). This is handled by allowing carefully circumscribed mention of Vand similar

large collections asproper classes. In theories withproper classes the statement is not true

becauseproper classes cannot be elements.

Set theories with a universal set

There are set theories known to be consistent (if the usual set theory is consistent) in which the

universal set Vdoes exist (and is true). In these theories, Zermelo's axiom of separation doesnot hold in general, and the axiom of comprehension ofnaive set theory is restricted in a different

way.

The most widely studied set theory with a universal set is Willard Van Orman Quines New

Foundations. Alonzo Church and Arnold Oberschelp also published work on such set theories.

Church speculated that his theory might be extended in a manner consistent with Quines, [2] but this

is not possible for Oberschelps, since in it the singleton function is provably a set, [3] which leads

immediately to paradox in New Foundations.[4]

ZermeloFraenkel set theory and related set theories, which are based on the idea of the cumulative

hierarchy, do not allow for the existence of a universal set.

(11) Complex Instruction Set Computing

A complex instruction set computer (CISC) (pronounced / s sk/ ), is a computerwhere single

instructions can execute several low-level operations (such as a load from memory, an arithmetic

operation, and a memory store) and/or are capable of multi-step operations oraddressing modes

within single instructions. The term was retroactively coined in contrast to reduced instruction set

computer(RISC).

Examples of CISC instruction set architectures are System/360 through z/Architecture,PDP-11,

VAX, Motorola 68k, and x86.

(12) Paging

In computer operating systems, paging is one of the memory-management schemes by which a

computer can store and retrieve data from secondary storage for use in main memory. In the paging

memory-management scheme, the operating system retrieves data from secondary storage in same-

size blocks calledpages. The main advantage of paging is that it allows the physical address space ofa process to be noncontiguous. Before paging, systems had to fit whole programs into storage

contiguously, which caused various storage and fragmentation problems.[1]

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Paging is an important part ofvirtual memory implementation in most contemporary general-purpose

operating systems, allowing them to use disk storage for data that does not fit into physical Random-

access memory (RAM). Paging is usually implemented as architecture-specific code built into the

kernel of the operating system.

The main functions of paging are performed when a program tries to access pages that are notcurrently mapped to physical memory (RAM). This situation is known as apage fault. The operating

system must then take control and handle the page fault, in a manner invisible to the program.

Therefore, the operating system must:

1. Determine the location of the data in auxiliary storage.

2. Obtain an empty page frame in RAM to use as a container for the data.

3. Load the requested data into the available page frame.

4. Update thepage table to show the new data.

5. Return control to the program, transparently retrying the instruction that caused the page

fault.

Because RAM is faster than auxiliary storage, paging is avoided until there is not enough RAM to

store all the data needed. When this occurs, a page in RAM is moved to auxiliary storage, freeing up

space in RAM for use. Thereafter, whenever the page in secondary storage is needed, a page in RAM

is saved to auxiliary storage so that the requested page can then be loaded into the space left behind

by the old page. Efficient paging systems must determine the page to swap by choosing one that is

least likely to be needed within a short time. There are various page replacement algorithms that try

to do this.

(13) Validation & Verification

Validation:-

1. The process of determining whether a value in a table's data cell its within the allowable

range or is a member of a set of acceptable values.

2. The process of evaluating software to ensure compliance with established requirements and

design criteria.

Verification:-The process of evaluating an application to determine whether or not the work products of a stage ofa software development lifecycle fulfill the requirements established during the previous stage.

(14) Spiral Model

An iterative version of the waterfall software development model. Rather than producing the

entire software product in one linear series of steps, the spiral development model implies that

specific components or sets of components of the software product are brought through each of the

stages in the software development lifecycle before development begins on the next set. Once one

component is completed, the next component in order of applicability is developed. Often, a

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dependency tree is used where components that have other components dependent upon them are

developed first.

(15) Distributed databaseA distributed database is a database that is under the control of a central database management

system (DBMS) in which storage devices are not all attached to a common CPU. It may be stored in

multiple computers located in the same physical location, or may be dispersed over a network of

interconnected computers.

Collections of data (e.g. in a database) can be distributed across multiple physical locations. A

distributed database can reside on network servers on the Internet, on corporate intranets or extranets,

or on other company networks. Replication and distribution of databases improve database

performance at end-user worksites.

To ensure that the distributive databases are up to date and current, there are two processes:

replication and duplication. Replication involves using specialized software that looks for changes in

the distributive database. Once the changes have been identified, the replication process makes all

the databases look the same. The replication process can be very complex and time consuming

depending on the size and number of the distributive databases. This process can also require a lot of

time and computer resources. Duplication on the other hand is not as complicated. It basically

identifies one database as a master and then duplicates that database. The duplication process is

normally done at a set time after hours. This is to ensure that each distributed location has the same

data. In the duplication process, changes to the master database only are allowed. This is to ensure

that local data will not be overwritten. Both of the processes can keep the data current in all

distributive locations.

Besides distributed database replication and fragmentation, there are many other distributed database

design technologies. For example, local autonomy, synchronous and asynchronous distributed

database technologies. These technologies' implementation can and does depend on the needs of the

business and the sensitivity/confidentiality of the data to be stored in the database, and hence the

price the business is willing to spend on ensuring data security, consistency and integr

(16) Demoralization

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demoralization is the process of attempting to optimize the read performance of a database by

adding redundant data or by grouping data. In some cases, demoralization helps cover up the

inefficiencies inherent in relational database software. A relational normalized database imposes a

heavy access load over physical storage of data even if it is well tuned for high performance.

A normalized design will often store different but related pieces of information in separate logicaltables (called relations). If these relations are stored physically as separate disk files, completing a

database query that draws information from several relations (a join operation) can be slow. If manyrelations are joined, it may be prohibitively slow. There are two strategies for dealing with this. The

preferred method is to keep the logical design normalized, but allow the database management

system (DBMS) to store additional redundant information on disk to optimize query response. In this

case it is the DBMS software's responsibility to ensure that any redundant copies are kept consistent.

This method is often implemented in SQL as indexed views (Microsoft SQL Server) or materialized

views (Oracle). A view represents information in a format convenient for querying, and the index

ensures that queries against the view are optimized.

The more usual approach is to deformalize the logical data design. With care this can achieve asimilar improvement in query response, but at a costit is now the database designer's responsibility

to ensure that the deformalized database does not become inconsistent. This is done by creating rules

in the database called constraints, that specify how the redundant copies of information must be kept

synchronized. It is the increase in logical complexity of the database design and the added

complexity of the additional constraints that make this approach hazardous. Moreover, constraints

introduce a trade-off, speeding up reads (SELECT in SQL) while slowing down writes (INSERT,

UPDATE, and DELETE). This means a deformalized database under heavy write load may actually

offerworse performance than its functionally equivalent normalized counterpart.

A deformalized data model is not the same as a data model that has not been normalized, and

renormalization should only take place after a satisfactory level of normalization has taken place and

that any required constraints and/or rules have been created to deal with the inherent anomalies in the

design. For example, all the relations are in third normal form and any relations with join and multi-

valued dependencies are handled appropriately.

(17)ADSL (Asymmetric Digital Subscriber Line)

ADSL Stands for "Asymmetric Digital Subscriber Line." ADSL is a type ofDSL, whichis a method of transferring data over copper telephone lines. While symmetrical DSL (SDSL)

uploads and downloads data at the same speed, ADSL has different maximum data transfer rates for

uploading and downloading data.

For example, an ADSL connection may allow download rates of 1.5Mbps, while upload speeds may

only reach 256Kbps. Since most users download much more data than they upload, this difference

usually does not make a noticeable impact on Internet access speeds. However, for Web servers or

other computers that send a lot of data upstream, ADSL would be an inefficient choice.

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(18) Natural language processing

ASIMOuses sensors and intelligent algorithms to avoid obstacles and navigate stairs.

Main article: Natural language processing

Natural language processing gives machines the ability to read and understand the languages that

humans speak. Many researchers hope that a sufficiently powerful natural language processing

system would be able to acquire knowledge on its own, by reading the existing text available over

the internet. Some straightforward applications of natural language processing include information

retrieval (or text mining) and machine translation.

Perception

Main articles: Machine perception, Computer vision, and Speech recognition

Machine perception is the ability to use input from sensors (such as cameras, microphones, sonar

and others more exotic) to deduce aspects of the world. Computer vision is the ability to analyze

visual input. A few selected sub problems are speech recognition, [facial recognition and object

recognition.

(19) Domain

While the term "domain" is often used synonymously with "domain name," it also has a definition

specific to local networks.

A domain contains a group of computers that can be accessed and administered with a common set

of rules. For example, a company may require all local computers to be networked within the same

domain so that each computer can be seen from other computers within the domain or located from a

centralserver. Setting up a domain may also block outside traffic from accessing computers within

the network, which adds an extra level of security

While domains can be setup using a variety of networking software, including applications from

Novell and Oracle, Windows users are most likely familiar with Windows Network Domains. This

networking option is built into Windows and allows users to create or join a domain. The domain

may or may not be password-protected. Once connected to the domain, a user may view othercomputers within the domain and can browse the shared files and folders available on the connected

systems.

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Windows XP users can browse Windows Network Domains by selecting the "My Network Places"

option on the left side of an open window. You can create a new domain by using the Network Setup

Wixard. Mac users using Mac OS X 10.2 or later can also connect to a Windows Network by

clicking the "Network" icon on the left side of an open window. This will allow you to browse localMacintosh and Windows networks using theSMB protocol

(20) Applet

This a Java program that can be embedded in a Web page. The difference between a standard Java

application and a Java applet is that an applet can't access system resources on the local computer.System files and serial devices (modems, printers, scanners, etc.) cannot be called or used by the

applet. This is for security reasons -- nobody wants their system wiped out by a malicious applet on

some wacko's Web site. Applets have helped make the Web more dynamic and entertaining and have

given a helpful boost to the Java programming language.

(21) Primary key

Primary key means main key

Def.:- A primary key is one which uniquely identifies a row of a table. this key does not allow nullvalues and also does not allow duplicate values.

for example:

empno empname salary

1 firoz 35000

2 basha 34000

3 chintoo 40000

it will not the values as follows:

1 firoz 35000

1 basha 34000chintoo 35000

Definition : A primary key, also called a primary keyword, is a key in a relational databasethat is unique for each record. It is a unique identifier, such as a driver license number, telephone

number (including area code), or vehicle identification number (VIN). A relational database must

always have one and only one primary key. Primary keys typically appear as columns in relational

database tables.

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The choice of a primary key in a relational database often depends on the preference of the

administrator. It is possible to change the primary key for a given database when the specific needs

of the users changes. For example, the people in a town might be uniquely identified according to

their driver license numbers in one application, but in another situation it might be more convenient

to identify them according to their telephone numbers.

(22) EncryptionEncryption is the coding or scrambling of information so that it can only be decoded and read by

someone who has the correct decoding key. Encryption is used in secure Web sites as well as othermediums of data transfer. If a third party were to intercept the information you sent via an encrypted

connection, they would not be able to read it. So if you are sending a message over the office

network to your co-worker about how much you hate your job, your boss, and the whole dang

company, it would be a good idea to make sure that you send it over an encrypted line.

(23)Two-phase locking

In databases and transaction processing (transaction management), Two-phase locking, (2PL) is a

concurrency control locking protocol, or mechanism, which guarantees Serializability (e.g., seeBernstein et al. 1987, Weikum and Vossen 2001). It is also the name of the resulting class (set) of

transaction schedules. Using locks that block processes, 2PL may be subject to deadlocks that resultfrom the mutual blocking of two transactions or more.

2PL is a super-class ofStrong strict two-phase locking (SS2PL), also called Rigorousness, which

has been widely utilized for concurrency control in general-purpose database systems since their

early days in the 1970s. SS2PL implementation has many variants. SS2PL was called in the past

Strict 2PL, and confusingly it is still called so by some. SS2PL is also a special case (subclass) of

Commitment ordering(Commit ordering; CO), and inherits many of CO's useful properties.

2PL in its general form, as well as when combined with Strictness, i.e., Strict 2PL (S2PL), are notknown to be utilized in practice.

Two-phase locking

According to the two-phase locking protocol, a transaction handles its locks in two distinct,

consecutive phases during the transaction's execution:

1. Expanding phase (number of locks can only increase): locks are acquired and no locks are

released.

2. Shrinking phase: locks are released and no locks are acquired.

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The serializability property is guaranteed for a schedule with transactions that obey the protocol. The

2PL schedule class is defined as the class of all the schedules comprising transactions with dataaccess orders that could be generated by the 2PL protocol.

Typically, without explicit knowledge in a transaction on end of phase-1, it is safely determined only

when a transaction has entered its ready state in all its processes (processing has ended, and it isready to be committed; no additional locking is possible). In this case phase-2 can end immediately

(no additional processing is needed), and actually no phase-2 is needed. Also, if several processes

(two or more) are involved, then a synchronization point (similar to atomic commitment) among

them is needed to determine end of phase-1 for all of them (i.e., in the entire distributed transaction),

to start releasing locks in phase-2 (otherwise it is very likely that both 2PL and Serializability are

quickly violated). Such synchronization point is usually too costly (involving a distributed protocol

similar to atomic commitment), and end of phase-1 is usually postponed to be merged with

transaction end (atomic commitment protocol for a multi-process transaction), and again phase-2 is

not needed. This turns 2PL to SS2PL (see below). All known implementations of 2PL in products

are SS2PL based.

(24) ATA (Advanced Technology Attachment)ATA Stands for "Advanced Technology Attachment." It is a type of disk drive that integrates the

drive controller directly on the drive itself. Computers can use ATA hard drives without a specific

controller to support the drive. The motherboard must still support an ATA connection, but a

separate card (such as a SCSI card for a SCSI hard drive) is not needed. Some different types of

ATA standards include ATA-1, ATA-2 (a.k.a. Fast ATA), ATA-3, Ultra ATA (33 MBps maximum

transfer rate), ATA/66 (66 MBps), and ATA/100 (100MBps).

The term IDE, or "Integrated Drive Electronics," is also used to refer to ATA drives.Sometimes (to

add extra confusion to people buying hard drives), ATA drives are labeled as "IDE/ATA."

Technically, ATA uses IDE technology, but the important thing to know is that they refer to the

same thing.

(25) Exception Handling

An exception is a problem that arises during the execution of a program. An exception can occur for

many different reasons, including the following:

A user has entered invalid data.

A file that needs to be opened cannot be found.

A network connection has been lost in the middle of communications, or the JVM has run out

of memory.

Some of these exceptions are caused by user error, others by programmer error, and others by

physical resources that have failed in some manner.

To understand how exception handling works in Java, you need to understand the three categories of

exceptions:

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Checked exceptions: Achecked exception is an exception that is typically a user error or a problem

that cannot be foreseen by the programmer. For example, if a file is to be opened, but the file cannot

be found, an exception occurs. These exceptions cannot simply be ignored at the time of compilation.

Runtime exceptions: A runtime exception is an exception that occurs that probably could have been

avoided by the programmer. As opposed to checked exceptions, runtime exceptions are ignored atthe time of compliation.

Errors: These are not exceptions at all, but problems that arise beyond the control of the user or the

programmer. Errors are typically ignored in your code because you can rarely do anything about an

error. For example, if a stack overflow occurs, an error will arise. They are also ignored at the time

of compilation.

(26) ClusterA group of sectors on a disk. While a sectoris the smallest unit that can be accessed on your harddisk, a cluster is a slightly larger unit that is used to organize and identify files on the disk. Most files

take up several clusters of disk space.

Each cluster has a unique ID, which enables the hard drive to locate all the clusters on the disk. After

reading and writing many files to a disk, some clusters may remain labeled as being used even

though they do not contain any data. These are called "lost clusters" and can be fixed using ScanDisk

on Windows or the Disk Utility program on the Mac. This is why running a disk utility or

defragmentation program may free up space on your hard disk.

(27) OSIOpen Systems Interconnection (OSI) model is a reference model developed by ISO (International

Organization for Standardization) in 1984, as a conceptual framework of standards for

communication in the network across different equipment and applications by different vendors. It is

now considered the primary architectural model for inter-computing and internetworking

communications. Most of the network communication protocols used today have a structure based on

the OSI model. The OSI model defines the communications process into 7 layers, which divides the

tasks involved with moving information between networked computers into seven smaller, more

manageable task groups. A task or group of tasks is then assigned to each of the seven OSI layers.

Each layer is reasonably self-contained so that the tasks assigned to each layer can be implemented

independently. This enables the solutions offered by one layer to be updated without adverselyaffecting the other layers.

OSI 7 Layers Reference Model For Network Communication

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OSI model with comparison of TCP/IP

Layer 7:Application Layer

Defines interface to user processes for communication and data transfer in network

Provides standardized services such as virtual terminal, file and job transfer and operations

Layer 6:Presentation Layer

Masks the differences of data formats between dissimilar systems

Specifies architecture-independent data transfer format

Encodes and decodes data; Encrypts and decrypts data; Compresses and decompresses data

Layer 5:Session Layer

Manages user sessions and dialogues

Controls establishment and termination of logic links between users

Reports upper layer errors

Layer 4:Transport Layer

Manages end-to-end message delivery in network

Provides reliable and sequential packet delivery through error recovery and flow control mechanisms

Provides connectionless oriented packet delivery

Layer 3:Network Layer

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Determines how data are transferred between network devices

Routes packets according to unique network device addresses

Provides flow and congestion control to prevent network resource depletion

Layer 2:Data Link Layer

Defines procedures for operating the communication links

Frames packets

Detects and corrects packets transmit errors

Layer 1:Physical Layer

Defines physical means of sending data over network devices

Interfaces between network medium and devices

Defines optical, electrical and mechanical characteristics

(28) Extranet

If you know the difference between the Internet and an intranet, you have an above average

understanding of computer terminology. If you know what an extranet is, you may be in the top

echelon.

An extranet actually combines both the Internet and an intranet. It extends an intranet, or internal

network, to other users over the Internet. Most extranets can be accessed via a Web interface using a

Web browser. Since secure or confidential information is often accessible within an intranet,

extranets typically require authentication for users to access them.

Extranets are often used by companies that need to share selective information with other businesses

or individuals. For example, a supplier may use an extranet to provide inventory data to certain

clients, while not making the information available to the general public. The extranet may also

include a secure means of communication for the company and its clients, such as a support ticket

system or Web-based forum.

(29) COCOMO MODEL

Overview of COCOMO

The COCOMO cost estimation model is used by thousands of software project managers, and is

based on a study of hundreds of software projects. Unlike other cost estimation models, COCOMO is

an open model, so all of the details are published, including:

The underlying cost estimation equations

Every assumption made in the model (e.g. "the project will enjoy good management") Every definition (e.g. the precise definition of the Product Design phase of a project)

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The costs included in an estimate are explicitly stated (e.g. project managers are included,

secretaries aren't)

Because COCOMO is well defined, and because it doesn't rely upon proprietary estimation

algorithms, Costar offers these advantages to its users:

COCOMO estimates are more objective and repeatable than estimates made by methods

relying on proprietary models

COCOMO can be calibrated to reflect your software development environment, and to

produce more accurate estimates

Costar is a faithful implementation of the COCOMO model that is easy to use on small projects, and

yet powerful enough to plan and control large projects.

Typically, you'll start with only a rough description of the software system that you'll be developing,

and you'll use Costar to give you early estimates about the proper schedule and staffing levels. As

you refine your knowledge of the problem, and as you design more of the system, you can use Costarto produce more and more refined estimates.

Costar allows you to define a software structure to meet your needs. Your initial estimate might be

made on the basis of a system containing 3,000 lines of code. Your second estimate might be more

refined so that you now understand that your system will consist of two subsystems (and you'll have

a more accurate idea about how many lines of code will be in each of the subsystems). Your next

estimate will continue the process -- you can use Costar to define the components of each subsystem.

Costar permits you to continue this process until you arrive at the level of detail that suits your needs.

One word of warning: It is so easy to use Costar to make software cost estimates, that it's possibleto misuse it -- every Costar user should spend the time to learn the underlying COCOMO

assumptions and definitions fromSoftware Engineering Economics andSoftware Cost Estimation

with COCOMO II.

Introduction to the COCOMO Model

The most fundamental calculation in the COCOMO model is the use of the Effort Equation to

estimate the number of Person-Months required to develop a project. Most of the other COCOMO

results, including the estimates for Requirements and Maintenance, are derived from this quantity.

Source Lines of Code

The COCOMO calculations are based on your estimates of a project's size in Source Lines of Code

(SLOC). SLOC is defined such that:

Only Source lines that are DELIVERED as part of the product are included -- test drivers and

other support software is excluded

SOURCE lines are created by the project staff -- code created by applications generators is

excluded

One SLOC is one logical line of code

Declarations are counted as SLOC

Comments are not counted as SLOC

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The original COCOMO 81 model was defined in terms of Delivered Source Instructions, which are

very similar to SLOC. The major difference between DSI and SLOC is that a single Source Line of

Code may be several physical lines. For example, an "if-then-else" statement would be counted as

one SLOC, but might be counted as several DSI.

The Scale Drivers

In the COCOMO II model, some of the most important factors contributing to a project's duration

and cost are the Scale Drivers. You set each Scale Driver to describe your project; these Scale

Drivers determine the exponent used in the Effort Equation.

The 5 Scale Drivers are:

Precedentedness

Development Flexibility

Architecture / Risk Resolution

Team Cohesion Process Maturity

Cost Drivers

COCOMO II has 17 cost drivers you assess your project, development environment, and team to

set each cost driver. The cost drivers are multiplicative factors that determine the effort required to

complete your software project. For example, if your project will develop software that controls an

airplane's flight, you would set the Required Software Reliability (RELY) cost driver to Very High.

That rating corresponds to an effort multiplier of 1.26, meaning that your project will require 26%

more effort than a typical software project.

COCOMO II defines each of the cost drivers, and the Effort Multiplier associated with each rating.

Check the Costar help for details about the definitions and how to set the cost drivers.

COCOMO II Effort Equation

The COCOMO II model makes its estimates of required effort (measured in Person-Months PM)

based primarily on your estimate of the software project's size (as measured in thousands of SLOC,

KSLOC)):

Effort = 2.94 * EAF * (KSLOC)E

Where

EAF Is the Effort Adjustment Factor derived from the Cost Drivers

E Is an exponent derived from the five Scale Drivers

As an example, a project with all Nominal Cost Drivers and Scale Drivers would have an EAF of

1.00 and exponent, E, of 1.0997. Assuming that the project is projected to consist of 8,000 source

lines of code, COCOMO II estimates that 28.9 Person-Months of effort is required to complete it:

Effort = 2.94 * (1.0) * (8)1.0997 = 28.9 Person-Months

Effort Adjustment Factor

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The Effort Adjustment Factor in the effort equation is simply the product of the effort multipliers

corresponding to each of the cost drivers for your project.

For example, if your project is rated Very High for Complexity (effort multiplier of 1.34), and Low

for Language & Tools Experience (effort multiplier of 1.09), and all of the other cost drivers are

rated to be Nominal (effort multiplier of 1.00), the EAF is the product of 1.34 and 1.09.

Effort Adjustment Factor = EAF = 1.34 * 1.09 = 1.46


COCOMO II Schedule Equation

The COCOMO II schedule equation predicts the number of months required to complete your

software project. The duration of a project is based on the effort predicted by the effort equation:

Duration = 3.67 * (Effort)SE

Where

Effort Is the effort from the COCOMO II effort equation

SE Is the schedule equation exponent derived from the five Scale Drivers

Continuing the example, and substituting the exponent of 0.3179 that is calculated from the scale

drivers, yields an estimate of just over a year, and an average staffing of between 3 and 4 people:

Duration = 3.67 * (42.3)0.3179 = 12.1 months

Average staffing = (42.3 Person-Months) / (12.1 Months) = 3.5 people

The SCED Cost Driver

The COCOMO cost driver for Required Development Schedule (SCED) is unique, and requires a

special explanation.

The SCED cost driver is used to account for the observation that a project developed on an

accelerated schedule will require more effort than a project developed on its optimum schedule. A

SCED rating of Very Low corresponds to an Effort Multiplier of 1.43 (in the COCOMO II.2000

model) and means that you intend to finish your project in 75% of the optimum schedule (asdetermined by a previous COCOMO estimate). Continuing the example used earlier, but assuming

that SCED has a rating of Very Low, COCOMO produces these estimates:

Duration = 75% * 12.1 Months = 9.1 Months

Effort Adjustment Factor = EAF = 1.34 * 1.09 * 1.43 = 2.09


Average staffing = (60.4 Person-Months) / (9.1 Months) = 6.7 people

Notice that the calculation of duration isn't based directly on the effort (number of Person-Months)

instead it's based on the schedule that would have been required for the project assuming it had

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been developed on the nominal schedule. Remember that the SCED cost driver means "accelerated

from the nominal schedule".

The Costar command Constraints | Constrain Projectdisplays a dialog box that lets you trade off

duration vs. effort (SCED is set for you automatically). You can use the dialog box to constrain your

project to have a fixed duration, or a fixed cost.

(30) Firmware

Firmware is a software program or set of instructions programmed on a hardware device. It provides

the necessary instructions for how the device communicates with the other computer hardware. But

how can software be programmed onto hardware? Good question. Firmware is typically stored in the

flash ROM of a hardware device. While ROM is "read-only memory," flash ROM can be erased and

rewritten because it is actually a type of flash memory.

Firmware can be thought of as "semi-permanent" since it remains the same unless it is updated by a

firmware updater. You may need to update the firmware of certain devices, such as hard drives and

video cards in order for them to work with a new operating system. CD and DVD drive

manufacturers often make firmware updates available that allow the drives to read faster media.

Sometimes manufacturers release firmware updates that simply make their devices work more

efficiently

(31) Computer Graphics

A graphic is an image or visual representation of an object. Therefore, computer graphics are simply

images displayed on a computer screen. Graphics are often contrasted with text, which is comprised

ofcharacters, such as numbers and letters, rather than images.

Computer graphics can be either two or three-dimensional. Early computers only supported 2D

monochrome graphics, meaning they were black and white (or black and green, depending on the

monitor). Eventually, computers began to support color images. While the first machines only

supported 16 or 256 colors, most computers can now display graphics in millions of colors.

2D graphics come in two flavors rasterand vector. Raster graphics are the most common and are

used for digital photos, Web graphics, icons, and other types of images. They are composed of a

simple grid ofpixels, which can each be a different color. Vector graphics, on the other hand are

made up of paths, which may be lines, shapes, letters, or other scalable objects. They are often used

for creating logos, signs, and other types of drawings. Unlike raster graphics, vector graphics can be

scaled to a larger size without losing quality.

3D graphics started to become popular in the 1990s, along with 3D rendering software such as CAD

and 3D animation programs. By the year 2000, many video games had begun incorporating 3D

graphics, since computers had enough processing power to support them. Now most computers now

come with a 3D video card that handles all the 3D processing. This allows even basic home systems

to support advanced 3D games and applications.

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(32) Software Testing

Software testing is any activity aimed at evaluating an attribute or capability of a program or system

and determining that it meets its required results. Although crucial to software quality and widely

deployed by programmers and testers, software testing still remains an art, due to limitedunderstanding of the principles of software. The difficulty in software testing stems from the

complexity of software: we cannot completely test a program with moderate complexity. Testing is

more than just debugging. The purpose of testing can be quality assurance, verification and

validation, or reliability estimation. Testing can be used as a generic metric as well. Correctness

testing and reliability testing are two major areas of testing. Software testing is a trade-off between

budget, time and quality.

Software Testing Types:

Black box testing Internal system design is not considered in this type of testing. Tests are based

on requirements and functionality.

White box testing This testing is based on knowledge of the internal logic of an applications

code. Also known as Glass box Testing. Internal software and code working should be known for

this type of testing. Tests are based on coverage of code statements, branches, paths, conditions.

Unit testing Testing of individual software components or modules. Typically done by the

programmer and not by testers, as it requires detailed knowledge of the internal program design and

code. may require developing test driver modules or test harnesses.

Incremental integration testing Bottom up approach for testing i.e continuous testing of an

application as new functionality is added; Application functionality and modules should beindependent enough to test separately. done by programmers or by testers.

Integration testing Testing of integrated modules to verify combined functionality after

integration. Modules are typically code modules, individual applications, client and server

applications on a network, etc. This type of testing is especially relevant to client/server and

distributed systems.

Functional testing This type of testing ignores the internal parts and focus on the output is as per

requirement or not. Black-box type testing geared to functional requirements of an application.

System testing Entire system is tested as per the requirements. Black-box type testing that is based

on overall requirements specifications, covers all combined parts of a system.

End-to-end testing Similar to system testing, involves testing of a complete application

environment in a situation that mimics real-world use, such as interacting with a database, using

network communications, or interacting with other hardware, applications, or systems if appropriate.

Sanity testing - Testing to determine if a new software version is performing well enough to accept

it for a major testing effort. If application is crashing for initial use then system is not stable enough

for further testing and build or application is assigned to fix.

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Regression testing Testing the application as a whole for the modification in any module or

functionality. Difficult to cover all the system in regression testing so typically automation tools are

used for these testing types.

Acceptance testing -Normally this type of testing is done to verify if system meets the customer

specified requirements. User or customer do this testing to determine whether to accept application.

Load testing Its a performance testing to check system behavior under load. Testing an application

under heavy loads, such as testing of a web site under a range of loads to determine at what point the

systems response time degrades or fails.

Stress testing System is stressed beyond its specifications to check how and when it fails.

Performed under heavy load like putting large number beyond storage capacity, complex database

queries, continuous input to system or database load.

Performance testing Term often used interchangeably with stress and load testing. To check

whether system meets performance requirements. Used different performance and load tools to dothis.

Usability testing User-friendliness check. Application flow is tested, Can new user understand the

application easily, Proper help documented whenever user stuck at any point. Basically system

navigation is checked in this testing.

Install/uninstall testing - Tested for full, partial, or upgrade install/uninstall processes on different

operating systems under different hardware, software environment.

Recovery testing Testing how well a system recovers from crashes, hardware failures, or othercatastrophic problems.

Security testing Can system be penetrated by any hacking way. Testing how well the system

protects against unauthorized internal or external access. Checked if system, database is safe from

external attacks.

Comparison testing Comparison of product strengths and weaknesses with previous versions or

other similar products.

Alpha testing In house virtual user environment can be created for this type of testing. Testing is

done at the end of development. Still minor design changes may be made as a result of such testing.

Beta testing Testing typically done by end-users or others. Final testing before releasing

application for commercial purpose.

(33) Intranet

Contrary to popular belief, this is not simply a misspelling of "Internet." "Intra" means "internal" or

"within," so an Intranet is an internal or private network that can only be accessed within the

confines of a company, university, or organization. "Inter" means "between or among," hence the

difference between the Internet and an Intranet.

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Up until the last few years, most corporations used local networks composed of expensive

proprietary hardware and software for their internal communications.

(34) Sockets and Socket Programming

A socket is one of the most fundamental technologies of computer networking. Sockets allow

applications to communicate using standard mechanisms built into network hardware and operating

systems. Although network software may seem to be a relatively new "Web" phenomenon, socket

technology actually has been emp

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