الثلاثاء، 9 فبراير، 2016

What is Hardware?

 ?? What is Hardware 



Hardware is the physical, tangible components of a computer or other electronic device. The term hardware traditionally refers to the physical components of any technology, which is paired with human or animal power and skill to perform it's function.Computer hardware is usually paired with software to perform it's function, and the two together are referred to as a computer system. The first hardware considered to be useful for computations was the tally stick, in use from about 35,000 BC until the mid 20th century. The first hardware that received instructions from software was probably the Jacquard loom in the early 19th century.
Personal computer hardware consists of all electronic parts, with the exception of the enclosure case. Hardware found in all desktop and laptop personal computers include the motherboard, at least one processor, memory, storage, an output device such as a monitor, and at least one input device such as a keyboard or mouse. All cables, connectors, fans, and other tangible components are considered hardware as well. Although most desktop computers can be readily disassembled into the individual hardware components, many laptops have two or more components assembled in a way that makes separation difficult or impossible. Laptop processors, for example, are often soldered onto the motherboard.
Embedded systems and other electronic devices may use specialized hardware that is not compatible with other similar systems, alternatively they may use generic, standardized hardware. Portable media players such as the iPod usually have proprietary casings, screens, and circuitry. However, the storage facilities of most portable media players are standard flash memory or hard drives that can be exchanged between models. The hardware inside a wristwatch will almost always be proprietary, however many watches use the same batteries and standardized fittings for the wristband. Automobile computers often use almost identical cases and internal circuitry within each manufacturer, however the onboard software and wiring harness is different across models.



What is Linux ?

 ???What is Linux

Linux is an open source operating system. Although traditionally 

used on servers, Linux has recently been gaining acceptance on home desktop computers. Linux is often perceived as an 'alternative' operating system to Microsoft Windows or Apple OS-X due to its non-commercial nature. Linux is developed by a team of thousands of volunteers worldwide, and most distributions are freely distributed.
The name "Linux" technically refers only to the kernel of the operating system. Distributors take this kernel and add their own packages and programs to it, then distribute it as a distro. However, popular use refers to any Linux distro simply as "Linux", just as Windows XP and Windows 98 are both referred to simply as "Windows". It is the popular definition, and not the technical definition, that you will see referred to on this website.
Linux logo
Popular Linux distros include Red Hat, Fedora, SUSE, Debian, Ubuntu, Slackware, Gentoo, and Mandriva. There are literally thousands more. Note that Linux's GPL licence makes the forking of a distro possible- that is why Red Hat and Fedora are usually associated with one another. The same company distributes both of them, however to different users for different purposes. Another similar situation is seen between Debian and Ubuntu. Ubuntu is a Debian fork. That means that Ubuntu's developers adopt a stable Debian release and modify it to create Ubuntu. This practice is legal and encouraged in Linux circles.


What is an Operating System?

 ?? What is an Operating System



An operating system is the lowest-level program running on a computer. The operating system provides software interfaces for the computer hardware, basic input and output functions, file and network management, and memory allocation. On top of these functions the user may run a command line, web, or graphical user interface. Additionally, the operating systems of non-specialized home and office computers are able to run third-party programs that either extend the functionality of the computer, or provide alternative interfaces to the existing functions. These programs need not know what hardware the computer consists of: the operating system provides the hardware abstraction necessary for running a single program on millions of different possible hardware combinations.

Most home computers today use the Microsoft Windows operating system. Other operating systems, such as Apple Macintosh and Linux, have traditionally been termed as "alternative operating systems", implying that Windows is usually expected to be installed by default. However, the usability issues surrounding Windows Vista, combined with improvements in the usability of graphical user interfaces for Linux, have catalyzed renewed interest in Linux and Macintosh. Other concerns, such as restrictive licensing and DRM issues, are expected to further interest in alternative, mostly open source operating systems. Currently, Linux is the leading open source operating system, with many distributions consisting entirely of open source software.

an Operating System logo
The first computers had no operating systems. The hardware of these early systems was very specialized, and only certain types of programs would run on them. These programs, being so specialized, interfaced directly with the system's hardware. Thus, these programs were not portable and any changes in hardware required changes in the computer program. As computers became less specialized, and different companies began producing hardware, the need for abstraction layers that would allow programs to run on the various hardware became apparent. Hence the concept of the shared library was invented, the first of which provided uniform software interfaces to various hardware. Later, these libraries incorporated time-sharing management tools and automatic job switching functions. Thus, the operating system was born.

الجمعة، 5 فبراير، 2016

What is a Protocol ?

                 ?? What is a Protocol 


A protocol is a system of rules that define how something is to be done. In computer terminology, a protocol is usually an agreed-upon or standardized method for transmitting data and/or establishing communications between different devices. Just as two humans need to have a common language between them before they can begin to share ideas and information, so must computers have a common way of sending information between them. The Internet is often used as an example of a successful protocols-based system in which the implementation of key qualities of protocols, such as error correction and message formatting, are utilized and respected across a wide variety of hardware and software.
To demonstrate a common usage of a popular protocol, we can examine the Internet's TCP/IP protocol. Computers can communicate different types of information over TCP/IP such as text, pictures, VOIP (Voice Over Internet Protocol), and more. To indicate that a user wants the page "protocol.html" from the What-Is-What website, the web browser Firefox connects to the What-Is-What server and sends this information: "GET /what_is/protocol.html HTTP/1.1". The server knows that the request is divided into three sections by spaces, and knows what values to expect in each section. The first section specifies the type of request, in this case a GET request. The next section is the location request, in this case the file "protocol.html" which is located in the "what_is" directory. The final section is the transport protocol that the browser would like to use, in this case version 1.1 of HTTP (HyperText Transfer Protocol). If Firefox were to request these properties in a different order, say, with the GET section at the end instead of at the beginning, the web server would not be able to understand the request. The order, and type, of the request is defined in the TCP/IP suite of protocols.
a Protocol logo
In the previous example, we saw how one protocol, TCP/IP, was used to specify the use of another protocol, HTTP. This is an example of high- and low-level protocols and how they interact. TCP and IP are low-level protocols, that are used in establishing the basic connection between two computers on a network. However, just simply connecting does nothing practical, and information must actually be transferred. Just like the low-level protocol defines the properties of the connection, a high-level protocol (such as HTTP) defines the properties of the data transfer. In addition to the familiar HTTP protocol, other common Internet protocols include FTP (File Transfer Protocol), DHCP (Dynamic Host Configuration Protocol), SMTP (Simple Mail Transfer Protocol), POP3 (Post Office Protocol version 3), and IMAP (Internet Message Access Protocol). You have probably noticed that all these acronyms end in the letter "P". In fact, whenever encountered with an unfamiliar computer-related acronym that ends in "P", there is a very good chance that it defines a protocol.

What is the World Wide Web?

?? What is the World Wide Web 



The World Wide Web is a network of computers that serve webpages. The World Wide Web is a major component of the Internet, along with email, Usenet, ftp, and some other minor protocols. The term "world wide" refers to the global nature of the World Wide Web, and the term "web" refers to the interlinking of documents by means of hypertext. In simple terms, this means that documents on the Web (or WWW for short) can reference, or link to, other documents by simply stating on which machine they reside, and where on that machine. Computers that serve documents on the World Wide Web are called servers, and the programs used to connect to servers and to display webpages are called web browsers.
Documents on the World Wide Web are traditionally written in HTML, a major component of the web. HTML defines the appearance and content of a webpage, and usually links to other HTML pages via a Uniform Resource Identifier or Uniform Resource Locator (URL). The pages are transferred between computers via HTTP, the HyperText Transfer Protocol. The most familiar of these concepts is without doubt the URL, such as "http://what-is-what.com/what_is/world_wide_web.html". The first part: "http://" means that the document should be fetched using the HTTP protocol. The next part, "what-is-what.com/" is the name of the server on which the document resides. The last part: "what_is/world_wide_web.html" means that the document named "world_wide_web.html" resides in the "what_is" folder. Note the suffix ".html". Usually, file name extensions indicate in what format the file was written. In this case, the file is written in HTML. This is expected, as the file is meant to be accessed on the WWW.
the World Wide Web logo
The history of the The World Wide Web dates back to 1980. In that year Tim Berners-Lee, a physicist at CERN (the European Organization for Nuclear Research), devised a way for moving documents between remote computers. The proprietary system, named ENQUIRE, went through several monumental changes between 1980 and its public release in 1991. The physicists at CERN were in need of a simple way for non-computer literate scientists to exchange data between laboratories very far apart. Thus, a simple to learn language for creating documents in outline format was invented, called HTML. In order to transfer the documents between computers, a simple text-based protocol was needed, thus HTTP was invented. The computers that understood HTTP requests and served HTML documents in response were called servers, and the programs used to actually view the documents were called browsers. As the system of requesting and viewing documents could be used by a computer anywhere in the world by any compliant computer connected to a phone line, the system was called the World Wide Web.



الأربعاء، 27 يناير، 2016

What is Go-oo?

 ??What is Go-oo

Go-oo is a community-developed fork of Sun's Open Office office suit. Go-oo contains features and improvements that for technical or legal reasons cannot be included in Sun's version of Open Office. Most Linux distributions today use Go-oo instead of the standard Open Office packages, however, the splash screen and "About" dialogs usually remain the standard Open Office versions. This is at Sun's request, to enhance brand recognition and is in stark contrast to Mozilla's stance on Firefox forks, notably Iceweasel.
Although Open Office is open source, Sun does not accept contributions from outside Sun unless the developer gives Sun ownership of the contributed code. This ownership means that Sun can release this code under what ever license Sun chooses. Most code is released twice: once in OOo (Open Office) under the GPL license, and once again in Star Office under a proprietary Sun license. Star Office, Sun's commercial office suit, is built from much of the same code base as OOo, however being a proprietary application it cannot incorporate GPL code.
Go-oo logo
Community frustration regarding Sun's licensing requirements and refusal to add critical features catalyzed several forks of Open Office, which is explicitly permitted under the GPL license. Go-oo is the leading OOo fork for Linux, incorporating enhanced compatibility with competing office suits, snappier performance, and additional features. Compatibility with other office suites is provided by filters capable of parsing Microsoft Office's native OOXML format, MS Works, and Lotus Word Pro files. Snappier performance is seen is faster startup times and improved code profiling. Some of the more useful features in Go-oo that are missing from OOo include SVG support, VBA macro support, 3D transition effects, and a built-in multimedia framework.

What is an IP Address?

Internet Protocol Address (or IP Address) is an unique address that computing devices such as personal computers, tablets, and smartphones use to identify itself and communicate with other devices in the IP network. Any device connected to the IP network must have an unique IP address within the network. An IP address is analogous to a street address or telephone number in that it is used to uniquely identify an entity.
Dotted Decimals
The traditional IP Addresses (known as IPv4) uses a 32-bit number to represent an IP address, and it defines both network and host address. A 32-bit number is capable of providing roughly 4 billion unique numbers, and hence IPv4 addresses running out as more devices are connected to the IP network. A new version of the IP protocol (IPv6) has been invented to offer virtually limitless number of unique addresses. An IP address is written in "dotted decimal" notation, which is 4 sets of numbers separated by period each set representing 8-bit number ranging from (0-255). An example of IPv4 address is 216.3.128.12, which is the IP address previously assigned to iplocation.net.
An IPv4 address is divided into two parts: network and host address. The network address determines how many of the 32 bits are used for the network address, and remaining bits for the host address. The host address can further divided into subnetwork and host number.
Class A, B, C and CIDR networks
Traditionally IP network is classified as A, B or C network. The computers identified the class by the first 3 bits (A=000, B=100, C=110), while humans identify the class by first octet(8-bit) number. With scarcity of IP addresses, the class-based system has been replaced by Classless Inter-Domain Routing (CIDR) to more efficiently allocate IP addresses.
ClassNetwork AddressNumber of HostsNetmask
CIDR/4240,435,456240.0.0.0
CIDR/5134,217,728248.0.0.0
CIDR/667,108,864252.0.0.0
CIDR/733,554,432254.0.0.0
A/8 (1-126)16,777,216255.0.0.0
CIDR/98,388,608255.128.0.0
CIDR/104,194,304255.192.0.0
CIDR/112,097,152255.224.0.0
CIDR/121,048,576255.240.0.0
CIDR/13524,288255.248.0.0
CIDR/14262,144255.252.0.0
CIDR/15131,072255.254.0.0
B/16 (128-191)65,534255.255.0.0
CIDR/1732,768255.255.128.0
CIDR/1816,384255.255.192.0
CIDR/198,192255.255.224.0
CIDR/204,096255.255.240.0
CIDR/212,048255.255.248.0
CIDR/221,024255.255.252.0
CIDR/23512255.255.254.0
C/24 (192-223)256255.255.255.0
CIDR/25128255.255.255.128
CIDR/2664255.255.255.192
CIDR/2732255.255.255.224
CIDR/2816255.255.255.240
CIDR/298255.255.255.248
CIDR/304255.255.255.252
Note: (1) 127 Network Address reserved for loopback test. (2) Class D (224-247, Multicast) and Class E (248-255, Experimental) are not intended to be used in public operation. 

Public and Private IP Addresses 

In order to maintain uniqueness within global namespace, the IP addresses are publicly registered with the Network Information Center (NIC) to avoid address conflicts. Devices that need to be publicly identified such as web or mail servers must have a globally unique IP address, and they are assigned a public IP address. Devices that do not require public access may be assigned a private IP address, and make it uniquely identifiable within one organization. For example, a network printer may be assigned a private IP address to prevent the world from printing from it. To allow organizations to freely assign private IP addresses, the NIC has reserved certain address blocks for private use. A private network is a network that uses RFC 1918 IP address space. The following IP blocks are reserved for private IP addresses.
ClassStarting IP AddressEnding IP Address
A10.0.0.010.255.255.255
B172.16.0.0172.31.255.255
C192.168.0.0192.168.255.255
In addition to above classful private addresses, 169.254.0.0 through 169.254.255.255 addresses are reserved for Zeroconf (or APIPA, Automatic Private IP Addressing) to automatically create the usable IP network without configuration.

What is loopback IP address? 

The loopback IP address is the address used to access itself. The IPv4 designated 127.0.0.1 as the loopback address with the 255.0.0.0 subnet mask. A loopback interface is also known as a virtual IP, which does not associate with hardware interface. On Linux systems, the loopback interface is commonly called lo or lo0. The corresponding hostname for this interface is called localhost.
The loopback address is used to test network software without physically installing a Network InterfaceCard (NIC), and without having to physically connect the machine to a TCP/IP network. A good example of this is to access the web server running on itself by using http://127.0.0.1 or http://localhost.