Arsip Untuk 2014

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Sunday, November 23, 2014

Définition ANSI ( American National Standart Institute )

Stands for "American National Standards Institute." ANSI is a non-profit organization based in the United States that works to develop and promote standards in the United States and around the world. By standardizing new products and technologies, both ANSI strengthens the US position on the world market and helps ensure the integrity and safety of products.

ANSI was originally called the "American Technical Standards Committee" (AESC), which was formed in 1918 AESC has worked with the American Institute of Electrical Engineers (IEEE now) and several other organizations to develop standards engineering. In 1928, the AESC was reorganized and renamed the "American Standards Association" (ASA). The ASA started developing partnerships with global organizations such as ISO and helped promote American standards in abroad. in 1969, the ASA was renamed to the ANSI standard. for decades, ANSI continued to promote national and international standards.

By standardizing new technologies, ANSI helps companies and government agencies to create products and services compatible. For example, when ANSI normalizes a specific type of hardwareport, computer manufacturers can build machines with standard port and know that it will be compatible with third-party devices. When ANSI standardized file format, software developers can support the format in their programs because the format information is publicly available.

When a new standard is accredited by ANSI, this means that the standard meets the requirements of the organization in terms of transparency, balance and consensus. In other words, only the standards that meet a process due to rigorous approval guidelines become accredited standards. This ensures that all accredited by ANSI standards apply to manufacturers and consumers.

Additional information on the ANSI standard can be found on the official website of the ANSI standard.

Définition ARP ( Address Resolution Protocol )

Stands for "Address Resolution Protocol". ARP is a protocol used to map an IP address to a computer connected to a LAN. Since each computer has a unique physical address called MAC address, ARP translates IP address to the MAC address. This ensures that each computer has a unique network identification.

The Address Resolution Protocol is used when the information sent to the network arrives at the gateway, which serves as the network entry point. The gateway uses ARP to find the computer's MAC address based on the IP address, the data is sent. The ARP typically considers this information in a table called "ARP cache." If the address is found, the information is transmitted to the gateway, which will send the incoming data to the appropriate machine. It can also convert the data to correct network format if necessary.

If the address is not found, the ARP broadcasts a "request packet" to other machines on the network to see if the IP address belongs to a device that is not in the ARP cache. If a system is valid, the information will be forwarded to the gateway and the ARP cache will be updated with the new information. by updating the ARP cache, future requests for that IP address will be much faster. While this may seem as a complex process, it usually only takes a split second to complete. If only it were that easy to find old recipes where you need it

Définition ASCII

Stands for "ASCII." ASCII character encoding provides a standard way to represent characters by using numeric codes. These include uppercase English letters and lowercase letters, numbers and punctuation symbols.

ASCII uses 7 bits to represent each character. For example, a capital "T" is represented by the number 84 and a lower case "t" is represented by 116. Other keys are also mapped to the standard ASCII values. For example, the Escape (ESC) is represented by 27 and the Delete key (LED) is represented as 32 ASCII codes can also be displayed as hexadecimal values instead of decimal numbers listed above. For example, the ASCII value of the Esc key in hex is "1B" and the hex value of the delete key is "7F".

Since ASCII uses 7 bits, it only supports 2 ^ 7, or 128 values. Therefore, the standard ASCII characters is limited to 128 characters. While this is sufficient to represent all the letters, numbers and standard English punctuation, it is not enough to represent all special characters or characters from other languages. Even ASCII, which supports the values of 8-bit or 256 characters, does not include enough characters to accurately represent all languages. Therefore, other character sets, such as Latin-1 (ISO-8859-1), UTF-8 and UTF-16 are commonly used for documents and Web pages that require other characters.

Tuesday, November 4, 2014

Définition Biometrics

Biometrics refers to technologies used to detect and recognize human physical characteristics. In the world of computing, biometrics is often synonymous with "biometric authentication", a type of security clearance based on the biometric input.

There are several types of biometric authentication. Common examples include the scanning of fingerprints, retina scan, facial recognition and voice analysis. Facial recognition system, for example, uses a camera to capture an image of a person's face. The photograph is then recorded and processed using software biometrics. The software tries to match the scanned image with an image from a database of user photos. If the analysis is close enough to a specific user, the person will be allowed to continue.

In many cases, a biometric scan is similar to a connection. For example, some computers have a fingerprint reader that allows you to authenticate by swiping your finger on a sensor. Instead of entering a username and password, the finger scan provides your permission. Some retail outlets are now using handheld scanners to check the identity of persons as an alternative to entering a unique identification number. High security government buildings and offices may even require retinal scans to access certain areas of the building. In some cases, an access card, password or login is required in addition to a biometric analysis to provide additional security

Définition Boot Sector

The boot sector is a dedicated hard drive or other storage device containing the data used to start a computer system section. It includes the Master Boot Record (MBR), which is accessible during the boot sequence.

The boot sector is usually located at the beginning of a disc before the first partition. It includes the separation plan, which identifies all the partitions on the disk. It also defines the partition that contains the starting data (such as the operating system). This allows the computer knows how to access at boot partition. Therefore, if the boot sector of a disk becomes corrupted or contains invalid data, the computer may not be able to boot from the disc. If this happens, you must run a disk utility or antivirus to try to solve the problem.

Définition Boot Sequence

Whenever a computer starts up, it goes through a series of processes first. This sequence of events is called a "boot sequence." During the startup sequence, the computer activates the necessary hardware and loads the appropriate software so that the user can interact with the machine.

The boot sequence begins with access to the BIOS of the computer on Windows PC or a Macintosh system ROM. BIOS ROM and contain basic instructions that tell the computer how to start. These instructions are then transmitted to the central processing unit of the computer, which begins to load information into the system RAM. Once the boot disk or valid boot disk is found, the computer begins to load the operating system in the system memory. After the operating system finishes loading, the computer is ready to use.

The startup sequence may last from a few seconds to several minutes, depending on the configuration of the computer. If the system boots from a CD or DVD, the startup time can be significantly longer if the computer is booted from a hard disk. Also, if your computer has been turned off unexpectedly, the start time may increase as the system can perform additional checks to make sure everything is OK.

Monday, November 3, 2014

Definition Cache

Cache, pronounced "cash" (not "catch" or "cashay") stores recently used the information to make it readily available at a later date. Computers integrate several types of caching to run more effectively, thereby improving performance. common types of caches include browser cache, disk cache, cache, and processor cache.

1. Browser Cache - Most data from the Web page web browsers default cache. For example, when you visit a web page, the browser can cache the code
HTML, images, and any CSS or JavaScript files referenced by the page. When you browse to other pages that use the same images, CSS or JavaScript, your browser will not have to re-download the files. Instead, the browser can simply load from the cache, which is stored on your local hard drive.

2. Cache - When an application is running, it may cache some data in system memory, or RAM. For example, if you work on a video project, the video editor can upload video clips and audio tracks on the hard disk into RAM. Since RAM can be accessed much faster than a hard disk, which reduces delay when importing and editing files.

3. Disk Cache - Most hard drives and SSDs include a small amount of RAM used for disk cache. A typical disk cache for a hard drive 1 terabyte is 32 megabytes, while a 2TB hard drive may have a cache of 64 MB RAM This small amount can make a big difference in performance of the car. For example, when you open a folder with many files, references to files can be automatically stored in the disk cache. The next time you open the folder, file list can instantly load instead of taking a few seconds to appear.

4. Cache CPU - CPU caches are even smaller than disk caches. This is because the processor cache contains tiny blocks of data, such as frequently used instructions, that can be quickly accessed by the CPU. Modern processors often contain an L1 cache that is right next to the processor and L2 cache which is a little further. The L1 cache is the smallest (about 64 Kb), while the L2 cache may be about 2 MB in size. Some high-end processors even include an L3 cache, which is larger than the L2 cache. When a processor accesses data from a higher level cache, it can also move data to the lower level cache for faster access next time.

Most cover is done in the background, so you will not even notice it happening. In fact, the only caches above you can control is the browser cache. You can open your browser preferences to display the cache settings and change the size of the cache of your browser or clear the cache if necessary.

Definition CDMA

Stands for "Code Division Multiple Access." CDMA is a wireless transmission technology that was developed during World War II by English allies to avoid having their scrambled transmissions. After the war, Qualcomm patented technology and commercially available as a digital cellular technology. Now CDMA is a popular method of communication used by many cell phone companies.

Unlike GSM and TDMA, CDMA transmits on all available frequencies. It does not affect an individual user's communication network frequency. This method, called multiplexing, which is difficult to jam transmissions during World War II. Because CDMA does not limit the frequency range of each user, it is more bandwidth available. This allows multiple users to communicate over the same network at the same time so that each user is assigned a specific frequency interval.

Because CDMA is a digital technology, the analog audio signals must be digitized before being transmitted over the network. CDMA is used by the 2G and 3G wireless communications and typically present in the frequency range from 800 MHz to 1.9 GHz wireless.

Definition Clean Room

A simple definition of what would be "the opposite of my room." But technically speaking, a clean room is a highly purified and regulated room for the production of sensitive equipment contamination. For example, the production of microprocessors is in a clean room, since smaller amounts of dust can create defects in production. therefore, the air in a clean room is continuously filtered. other aspects, such as temperature, humidity and pressure may be regulated as well.

Clean rooms are categorized according to a federal standard. A 1000 clean room class has no more than 1000 greater than 0.5 micron particles in a cubic foot of air. A 100 cleanroom class has no more than 100 particles. People who work in clean rooms must wear special suits that prevent them from contaminating the room. They almost look like space suits, but are not quite as heavy and does not require large boots to walk on the moon

Definition Clock Cycle

One clock cycle, or simply a "cycle" is an electronic pulse of a single processor. During each cycle, a processor can perform a basic operation such as retrieving an instruction, access to memory or writing data. Since simple commands can be performed at each cycle, the majority of CPU processes require several clock cycles.

In physics, the frequency of a signal is determined by the cycles per second, or "Hertz". Similarly, the frequency of a processor is measured in clock cycles per second. Since modern processors may complete millions of clock cycles each second processor speeds, are often measured in megahertz or gigahertz.

The frequency of a processor is also known that the clock speed of the processor. Although the clock speed is important in determining the overall performance of the processor, it is not the only factor. Since processors have instruction sets, they may differ in the number of cycles required to complete each instruction, or CPI (cycles per instruction). Therefore, some processors can operate more quickly than others, even at slower clock speeds.

Definition Alpha Software

Alpha software is software that is still in the phase of early detection. It's functional enough to be used, but it is dull and often lack many features that will be included in the final version of the program. The "alpha phase" of software development follows the steps of programming and design at first, but before the "beta" in which the software is much like the final version.

Since the alpha phase is the beginning of a cycle of software development, an alpha version usually includes significant bugs and usability issues. Therefore, any beta software can be provided to the public, an alpha version is only tested internally. The alpha stage is also important for competitive reasons, the developer may not want to disclose the new features of this software until shortly before the release date.

If a developer is to build a small application, it may be the only person who has ever tested the alpha version. Larger programs, however, are often tested in-house by a team of developers in the alpha phase. In some cases, several teams can work together on the alpha version of the software. Once the programmers have built a working version with all the features required, the lead developer may decide to set up a "feature freeze", which means no additional features are planned for the current version of the program. This often indicates the end of the alpha phase and the beginning of the beta phase of development.

Definition Zebibyte

Zebibyte is a storage unit data which is equal to 2 to the power 70, or 1,180,591,620,717,411,303,424 bytes.

While a zettabyte can be estimated as 10 ^ 21 bytes or 1,000,000,000,000,000,000,000 a zebibyte exactly 1,180,591,620,717,411,303,424 bytes. This avoids the ambiguity associated with the size of zettabytes. Is a zebibyte exbibytes 1024 precedes yobibyte measuring unit.

For a list of other units of measurement, see this section of the Help Center.

Abbreviation: ZiB

Definition Unicode

Unicode is an encoding standard universal character. It defines how individual characters are represented in text files, web pages, and other document types.

Unlike ASCII, which was designed to represent only basic English characters, Unicode has been designed to support characters of all languages of the world. The standard ASCII character set supports 128 characters, while Unicode can support approximately one million characters. Although ASCII uses one byte to represent each character, Unicode supports up to 4 bytes for each character.

There are several types of Unicode encodings, but UTF-8 and UTF-16 are the most common. UTF-8 has become the standard character encoding used on the Web and is also the default encoding used by many software. While UTF-8 supports up to four bytes per character, it would be inefficient to use four bytes to represent frequently used characters. Therefore, UTF-8 uses one byte to represent the common English characters. European (Latin), Hebrew, and Arabic characters are represented by two bytes, while three bytes are used for Chinese, Japanese, Korean, and other Asian characters. Additional Unicode characters can be represented with four bytes.

Definition Petaflops

Petaflop is a unit of measurement used to measure the performance of floating point unit, or FPU Processor. It can also be written as "petaFLOPS" or "PFLOPS." Since FLOPS stands for "Floating Point Operations Per Second", the term "petaflops" can be either singular (one petaflop) or multiple (two or more petaflops.) A petaflop is equal to 1,000 teraflops, or 1,000,000,000,000,000 FLOPS.

Petaflops are rarely used to measure the performance of a single computer, since only the fastest supercomputers run more than one petaflops. Therefore petaflops are most commonly used for the calculation of the processing power of multiple computers. In addition, since only measures flops floating point calculations, petaflops is not necessarily a good indicator of the overall performance of a computer. Other factors, such as the clock speed of the processor, the system bus speed, and the amount of RAM memory can also affect the speed at which the computer can perform calculations

Assembler Definition

An assembler program which is converted into machine code in assembler language. It takes the controls and basic operations of assembly code and converts into a binary code that can be recognized by a specific processor type.

Assemblers are similar in that they compilers to produce executable code. However, the most simplistic assemblers because they convert the low-level code (assembly language) into machine code. Since each assembly language is designed for a specific processor, the assembly of a program is performed using a simple mapping one-to-one assembly code into machine code. Compilers, on the other hand, must convert generic high-level source code into machine code for a specific processor.

Most programs are written in programming languages and high level are compiled directly into machine code using a compiler. However, in some cases, the code assembly can be used to customize the features and to ensure that they perform a specific manner. Therefore, FDI is often editors so they can create programs of the two languages high and low.

Assembly Language Definition

An assembly language is a language for low-level programming designed for a specific type of processor. It can be produced by compiling the source code of a programming language of high level (such as C / C ++), but can also be written from scratch. Assembly code can be converted to machine code using an assembler.

Like most compilers convert source code directly into machine code, software developers often create programs without using assembly language. However, in some cases, the code assembly can be used to refine a program. For example, a programmer can write a specific process in assembly language to make sure it works as efficiently as possible.

Although assembly languages differ between processor architectures, they often include instructions and similar operators. Examples of instructions supported by x86 processors.

      MOV - move data from one place to another

      ADD - add two values

      SUB - subtract one value from another value

      PUSH - push data onto a stack

      POP - pop data from stack

      JMP - jump to another location

      INT - interrupt a process

The following assembly language can be used to add the numbers 3 and 4:

mov eax, 3-3 loads in the register "eax"

mov ebx, 4-4 loads in the "ebx" register

add eax, ebx, ecx - adds "eax" and "ebx" and stores the result (7) "ecx"

Written in assembly language is a tedious process, because each operation must be performed at a very basic level. Although it is not necessary to use the code to create an assembly language learning editing computer program is often part of a computer program because it provides useful information on the work of the processors one way.

Command Line Interface Definition

Line interface (CLI or) is a text-based interface used for entering commands. In the early days of computing, before the mouse, it has been the standard method for interacting with a computer. While the graphical user interface (GUI) has largely replaced CLI, they are still included with many operating systems such as Windows and OS X.

There are many different types of command line interfaces, but the two most popular are DOS (Windows) and bash (for Linux and Mac OS X). Each uses its own CLI command syntax, but they all work the same way. For example, each has a CLI command prompt is displayed when the interface is ready to accept a command. When you type a command, it appears next to the command prompt and press Enter when the command is executed.

Examples of prompts for various command-line interfaces with the root folder as the current directory.

      Windows (DOS): C: \>

      OS X (bash): My iMac: / me $

      Linux (bash): [root @ myserver /] #

The standard way to change directories in most CLI is using the cd command followed by the directory path. If you use Windows, you can type cd C: \ Users to access the Users folder. If you are using OS X, you can type cd / Volumes / SSD / users (assuming that the drive name is "SSD"). Some other commands are identical between DOS and bash, but each CLI supports many different commands as well. For example, to list the contents of the current directory, type dir and ls DOS in the bash shell.

Most people prefer a standard graphical user to a single command line interface. However, some operations may actually be performed more quickly by using a keyboard instead of a mouse. Therefore, CLI are often used by network administrators and webmasters for common tasks such as file transfer and check the server status.

NOTE: A command line interface is sometimes called a console or terminal window. OS X includes a utility called "Terminal" which functions as the CLI for OS X

Bash Definiton

Bash, but generally are not capitalized, is an acronym for "Bourne-Again Shell" and is named after Stephen Bourne, the creator of the Unix shell "sh". It is a command language interpreter derived from sh can execute commands entered on input speed control and process text file.

Bash (bash) supports all commands of the original Bourne shell (sh), and many others. It also includes features of the Korn shell (ksh) and C shell (csh), such as command line editing, command syntax substitution, and command history. Bash also supports "the development braces," which is used to generate strings of related text. This operation provides an efficient way to search for file names and rename multiple files. Newer versions of Bash support regular expressions (Bash 3.0) and associative arrays (Bash 4.0).

Bash was originally developed by Brian Fox for the GNU project and was published in 1989. The bash was first distributed with the GNU operating system and later became the default shell for many Linux distributions and Mac OS X. The latest versions of Bash (versions 3 and 4) were developed by Chet Ramey and are currently published by the Free Software Foundation, the organization that distributes the GNU operating system

Root

In the computer world, "root" refers to the top-level directory of a file system. The word is derived from a root of the tree, as it represents the development of a hierarchical tree structure starting. The records of the tree represent the branches, while the actual files are considered the leaves. However, unlike a true tree of life, a tree data can be viewed upside down, with the root at the top and directories and subdirectories covering down.

The root node of a file system is also called the root directory. On a Windows PC, "C: \" is the root directory of the C drive on the Macintosh and Unix systems, the root directory is designated by a single slash ("/"). Similarly, the root directory of a website is simply the domain name followed by a slash (ie http: //www.techterms.com/). If you ever use a terminal program to view files and folders on a computer, you can use the command "cd /" (change directory to the root) to navigate to the root directory.

"Root" is also the name of the user who privleges administration on a Unix or Linux server. While most users can only access data within their own directory (eg "/ users / ~ fred /"), the root user can access a file on the hard disk. This allows the root user to install the updated system software, change the privileges of other users to access and perform other administrative tasks

DMZ "Demilitarized Zone"

Means "demilitarized zone." In computing, a DMZ is a section of a network between the intranet and a public network such as the Internet. It may contain a number of computer systems or single host.

The purpose of a DMZ is to protect an intranet from external access. By separating the intranet from hosts that can be accessed outside of a local area network (LAN), internal systems are protected against unauthorized access from outside the network. For example, a company may have an intranet consisting of their workstations. Public enterprise servers, such as web server and mail server can be placed in a DMZ so that they are separate workstations. If the servers were compromised by an external attack, internal systems would not be affected.

A DMZ can be configured in several different ways, but two of the most common include a basic firewall architectures and dual firewall. In a configuration of single firewall, intranet and DMZ are on separate networks, but share the same firewall, which monitors and filters traffic on the ISP. Configuration in a double firewall, a firewall is placed between the intranet and the DMZ and another firewall is placed between the DMZ and the Internet connection. This configuration is safer because it provides two layers of defense against external attacks.

NOTE: The term "DMZ" or "DMZ" is a military term used to describe a neutral zone where military operations are not allowed to take place. These areas usually exist along the boundary between two different countries. They act as a buffer and are designed to avoid unnecessary escalation of military action. Similarly, a DMZ is a neutral zone within a computer network which can be accessed by both internal and external computer systems.

OLED "Oragnic Light Emitting Diode"

Stands for "Organic Light Emitting Diode" and is pronounced "oh-led." OLED is a type of flat panel display similar to a screen that does not require a backlight. Instead, each LED in a panel OLED lights individually.

OLED screen has six layers that work together to produce color images. These layers include the following, from bottom to top:

     1. Substrate - the base structure that supports the panel; typically made of glass or plastic

     2. Anode - a transparent layer which withdraws electrons when an electric current passes through the

     3. conductive layer - containing organic molecules or polymers, such as polyaniline, which transfer electrical current from the emissive layer

     4. emissive layer - contains organic molecules or polymers such as polyfluorene that light when current is passed through the

      5. Cathode - injects electrons in the other layers when current flows therethrough

     6. Cover - the top layer of the screen protector; typically made of glass or plastic

How does an OLED screen?

OLED display light using a process called electrophosphorescence. While this may seem like an intimidating term, the process is relatively simple. The electric current flows from the cathode (negatively charged) at the anode (positively charged), causing electrons to move to the emitting layer. These electrons find "holes" (where electrons missing atoms) in the conductive layer and produce light when they fill these holes. The color of the light depends on the organic molecule as the current passes through the emissive layer.

Since the OLED illuminating diodes individually, there is no need for a backlight. This means that OLEDs can have darker blacks LED / LCD displays and use less electricity. Are thinner and can also be curved or even flexible. Although OLEDs have many advantages over LED / LCD displays, it was expensive to produce large OLED reliable. Therefore, OLEDs were more frequent in small electronic devices, such as smartphones and tablets. As production costs decrease OLED and reliability increases, the technology will become more commonly used in larger screens, such as televisions and computer monitors.

Sunday, November 2, 2014

Teleconference

A conference is a gathering of people in different locations using telecommunications. A basic conferencing can include audio, while other types of teleconferencing can include video and data sharing. Some common examples include conference calls, video conferencing, and online meetings.

The simplest and most widely used type is a conference call, since the only equipment required is a speaker. If a project needs to be discussed between more than two people in different places, they all can dial a telephone conference that will allow everyone to talk to each other simultaneously. A meeting of the Board of Directors may also double as a meeting if the board members attend remotely. Many boardrooms include a conference system that allows people to "call" the meeting by calling the telephone number of conference. This allows members of the board away from active participation in a meeting, even if they are not physically present.

Teleconferences can also include live video. These types of teleconferencing, videoconferencing often called, allow people to see each other in real time during a meeting remotely. A videoconference may be one way in which a user or group distance is displayed on a video stream, or in both directions, where both parties can see. In the early days of video conferencing, expensive equipment needed to set up a videoconference. Today, you can simply use the built-in camera to a computer and free software such as Skype to video conference with other users.

Thank you to the Internet, teleconferencing can also include data sharing. These types of conferences often use Web browsers as the user interface and are referred to online meetings. For example, you can use an online service like Join.me to share your screen with other users. You can even let someone else control your screen, which is excellent for remote troubleshooting. Companies can use an online service like WebEx to host an online hundreds or even thousands of participants. When hosting a web content, the presenter control and the screen is usually the only one who can be heard at the meeting. Participants are often provided with a chat window where they can ask questions and interact with the presenter

Sunday, October 12, 2014

Définition 802.11n

802.11n est une norme sans fil (Wi-Fi) qui a été introduit en 2007, Il prend en charge une gamme plus et les taux de transfert sans fil plus élevés que la norme précédente 802.11g.

Équipements 802.11n MIMO charge (multiple, multiples sur) les transferts de données, qui peuvent transmettre de multiples flux de données à la fois. Cette technologie double la portée d'un appareil sans fil. Par conséquent, un routeur sans fil qui utilise la norme 802.11n peut avoir deux fois le rayon de couverture comme un routeur 802.11g. Cela signifie un routeur 802.11n peut porter sur toute une famille, alors qu'un routeur 802.11g peut nécessiter routeurs supplémentaires pour combler le signal.

Les standards pris en charge 802.11g taux de transfert précédentes allant jusqu'à 54 Mbps. Les appareils utilisant la norme 802.11n peut transférer des données de plus de 100 Mbps. Avec une configuration optimisée, la norme 802.11n peut théoriquement supporter des débits allant jusqu'à 500 Mbps de transfert. C'est cinq fois plus rapide qu'un réseau Ethernet câblé norme 100Base-T.

Donc, si votre résidence n'est pas câblé à un réseau Ethernet, ce n'est pas une grosse affaire. La technologie sans fil peut enfin suivre le rythme avec le réseau filaire. Bien sûr, avec les vitesses plus rapides et plus grande plage qui 802.11n fournit, il est plus important que jamais de passe pour protéger votre réseau sans fil

Définition 802.11a

802.11a est une norme IEEE pour transmettre des données sur un réseau sans fil. Il utilise une bande de fréquences de 5 GHz et supporte des taux de transfert de données de 54 Mbps, ou 6,75 méga-octets par seconde.

La norme 802.11a a été publié en 1999, dans le même temps que le 802.11b. Alors que 802.11b uniquement pris en charge un débit de 11 Mbps de transfert de données, la plupart des routeurs et des cartes sans fil à l'époque ont été fabriqués en utilisant la norme 802.11b. Par conséquent, 802.11b est resté plus populaire que 802.11a depuis plusieurs années. En 2003, la norme 802.11a a été remplacée par la norme 802.11g, qui utilise la même bande de 2,4 GHz que 802.11a, mais supporte des débits allant jusqu'à 54 Mbps de transfert.

REMARQUE: Pour une connexion une 802.11a ait lieu, chaque périphérique sur le réseau sans fil doit prendre en charge la norme 802.11a. Par exemple, si une station de base diffuse un signal 802.11a, seuls les ordinateurs équipés de cartes Wi-Fi qui charge les normes 802.11a seront en mesure de reconnaître la station de base. Alors que de nombreux routeurs sont compatibles avec les anciennes normes, il peut être nécessaire de configurer manuellement certains routeurs pour fonctionner avec les périphériques 802.11a et 802.11b plus anciens.

Définition JSON ( Java Script Object Notation )

Stands pour "JavaScript Object Notation" et se prononce comme le nom de «Jason». JSON est un format de transfert de données basé sur le texte destiné à transmettre des données structurées. Il est le plus couramment utilisé pour transférer des données entre les applications Web et les serveurs Web.

JSON est souvent considéré comme une alternative à XML, un autre format d'échange de données en texte brut. Dans la plupart des cas, la représentation d'un objet JSON est plus compacte que la représentation XML car il ne nécessite pas de balises pour chaque élément. Voici un exemple d'un objet nommé "tokka pc» défini à la fois JSON et XML

JSON

{
"computer": {
"name": "tokka pc",
"components": {
"cpu": "Intel i5 3.4GHz", "ram": "8GB", "storage": "1TB HDD"
}
}
}

XML

<computer>
<name>tokka pc</name>
<components>
<cpu>Intel i5 3.4GHz</cpu>
<ram>16GB</ram>
<storage>1TB HDD</storage>
</components>
</computer>

Comme vous pouvez le voir, l'objet est représenté de manière plus efficace en JSON que dans XML. L'efficacité de JSON a aidé à devenir un choix populaire pour les applications web et il est maintenant souvent utilisé à la place de XML. Même les applications Ajax utilisent couramment JSON, si Ajax est techniquement pour "Asynchronous JavaScript and XML." Bien que la différence entre XML et JSON peut être négligeable pour les petites applications, faible surcharge de JSON peut aider à réduire la bande passante et d'autres ressources système utilisées par les sites Web à fort trafic.

Extension de fichier: .JSON

Définition Compact Disc File System (CDFS)

Stands pour "système de fichiers du disque compact." CDFS est un système de fichier utilisé pour stocker des données sur des CD. Il s'agit d'une norme publiée par l'Organisation internationale de normalisation (ISO) et est également connu comme "ISO 9660" Les disques qui stockent les données en utilisant la norme ISO 9660 peuvent être reconnus par de multiples plateformes, y compris Windows, Macintosh et Linux.

SFMC spécifie plusieurs propriétés du disque, y compris les attributs de volume, les attributs de fichiers, et l'emplacement des fichiers. Elle spécifie également la structure de données globale d'un CD, tels que la taille de l'en-tête et la zone de stockage de données du disque. Alors que le SFMC a été initialement conçu pour les disques en lecture seule session unique, une extension de la norme permet multisession écrit sur des disques CD-R. Cela signifie que de multiples volumes peuvent être stockés sur un seul CD.

La norme CDFS est utile pour la gravure de disques qui seront partagés entre plusieurs ordinateurs. Parce que CDFS n'est pas spécifique à un seul système d'exploitation, un disque gravé sur un Macintosh en utilisant le système de fichiers du disque compact peut être lu sur un ordinateur basé sur Windows ou Linux. Images de disque peuvent également être enregistrés en utilisant la norme du SFMC, qui peut être utilisé pour graver l'ISO 9660 disques. Ces fichiers sont généralement enregistrés avec une extension de fichier .ISO

Définition Batch File

Un fichier batch est un type de script qui contient une liste de commandes. Ces commandes sont exécutées en séquence et peut être utilisé pour automatiser des processus. Par exemple, certains programmes peuvent inclure un fichier de commandes qui exécute un certain nombre de commandes que le programme démarre. Un utilisateur peut également créer un fichier de commandes personnalisées pour automatiser les processus fastidieux tels que la copie de plusieurs répertoires ou de renommer plusieurs fichiers à la fois.

Les fichiers de commandes sont exécutées par le programme COMMAND.COM, qui fait partie de DOS et Windows. Par conséquent, les fichiers de commandes ne peuvent être exécutées dans le système d'exploitation Windows. Macintosh et Unix ont d'autres outils de script, comme AppleScript et commandes shell Unix, qui peuvent être utilisés pour des tâches similaires. Parce que les fichiers batch contiennent des commandes exécutables, il est important de ne pas ouvrir des fichiers de commandes inconnus sur votre disque dur ou en pièces jointes d'e-mail.

Extensions de fichier: .BAT, .CMD

Pétaflops Définition

Pétaflops est une unité de mesure utilisée pour mesurer la performance de virgule flottante de l'unité, ou FPU d'un processeur. Il peut également être écrit "petaFLOPS" ou "PFLOPS." Depuis FLOPS signifie «Floating Point Operations Per Second", le terme "pétaflops" peut être soit singulier (un pétaflops) ou plusieurs (deux ou plusieurs pétaflops). Un pétaflops est égal à 1 000 téraflops, ou 1.000.000.000.000.000 FLOPS.

Pétaflops sont rarement utilisés pour mesurer la performance d'un seul ordinateur, puisque seuls les superordinateurs les plus rapides tournent à plus d'un pétaflops. Par conséquent, pétaflops sont le plus souvent utilisés pour le calcul de la puissance de traitement des ordinateurs multiples. En outre, depuis flops seules mesures en virgule flottante calculs, pétaflops n'est pas nécessairement un bon indicateur de la performance globale d'un ordinateur. D'autres facteurs, tels que la vitesse du processeur de l'horloge, la vitesse du bus système, et la quantité de RAM peuvent aussi influer sur la rapidité avec laquelle un ordinateur peut effectuer des calculs.

Exabyte Définition

Un exabyte est 1018 ou 1.000.000.000.000.000.000 octets.

Un exaoctets (en abrégé "EB") est égal à 1,000 pétaoctets et précède l'unité de zettaoctet de mesure. Exabytes sont légèrement plus petites que exbibytes, qui contiennent 1,152,921,504,606,846,976 (260) octets.

L'unité de mesure de exabyte de mesure est si grand, il n'est pas utilisé pour mesurer la capacité des dispositifs de stockage de données. Même la capacité de stockage des plus grands centres de stockage en nuage est mesurée en pétaoctets, qui est une fraction d'un exaoctets. Au lieu de cela, exaoctets sont utilisés pour mesurer la somme de plusieurs réseaux de stockage ou la quantité de données transférées via Internet dans un certain laps de temps. Par exemple, plusieurs centaines de exaoctets de données sont transférés via Internet chaque année.

REMARQUE: Voir la liste de toutes les unités de mesure utilisées pour mesurer le stockage de données.

Définitions et taux de transfert de données entente

Le taux de transfert de données est couramment utilisé pour mesurer la quantité de données rapide est transféré d'un endroit à un autre. Par exemple, un disque dur peut avoir un taux de transfert de données maximum de 480 Mbps, alors que votre fournisseur de services Internet peut offrir une connexion Internet avec un taux de transfert de données maximum de seulement 1,5 Mbps.

Taux de transfert de données sont généralement mesurées en bits par seconde (bps), par opposition à d'octets par seconde, ce qui peut être compréhensible déroutant. Parce qu'il ya huit bits dans un octet, un taux de transfert de données soutenu de 80 Mbps transfère seulement 10 Mo par seconde. Bien que cela est source de confusion pour les consommateurs, les fournisseurs de services Internet doivent profiter de la mesure des taux de transfert de données en points de base, car il rend leurs vitesses d'accès à Internet sonnent 8x plus vite qu'ils ne le sont réellement.

Assembler Définition

Un assembleur est un programme qui convertit en langage assembleur en code machine. Elle prend les commandes et les opérations de base de code d'assemblage et les convertit en un code binaire qui peut être reconnu par un type spécifique de processeur.

Assembleurs sont semblables à compilateurs en ce qu'ils produisent du code exécutable. Cependant, les assembleurs plus simpliste car ils ne convertissent le code de bas niveau (langage d'assemblage) en code machine. Etant donné que chaque langage d'assemblage est conçu pour un processeur spécifique, l'assemblage d'un programme est exécutée en utilisant un simple mappage un-à-un code assembleur à partir du code machine. Compilateurs, d'autre part, doivent convertir générique code source de haut niveau en code machine pour un processeur spécifique.

La plupart des programmes sont écrits dans des langages de programmation de haut niveau et sont compilées directement en code machine en utilisant un compilateur. Cependant, dans certains cas, le code d'assemblage peut être utilisé pour personnaliser les fonctions et s'assurer qu'ils exercent d'une façon spécifique. Par conséquent, les IDE incluent souvent des assembleurs afin qu'ils puissent créer des programmes des deux langages de haut et de bas niveau.