Sunday, 4 September 2016
In a nutshell, a smartphone is a device that lets you make telephone calls, but also adds in features that, in the past, you would have found only on a personal digital assistant or a computer--such as the ability to send and receive e-mail and edit Office documents, for example.
But, to really understand what a smartphone is (and is not), and whether you should buy one, we'll start with a history lesson. In the beginning, there were cell phones and personal digital assistants (or PDAs). Cell phones were used for making calls--and not much else--while PDAs, like the Palm Pilot, were used as personal, portable organizers. A PDA could store your contact info and a to-do list, and could sync with your computer.
Eventually, PDAs gained wireless connectivity and were able to send and receive e-mail.
Cell phones, meanwhile, gained messaging capabilities, too. PDAs then added cellular phone features, while cell phones added more PDA-like (and even computer-like) features. The result was the smartphone.
Key Smartphone Features
While there is no standard definition of the term "smartphone" across the industry, we thought it would be helpful to point out what we here at About.com define as a smartphone, and what we consider a cell phone. Here are the features we look at:
In general, a smartphone will be based on an operating system that allows it to run applications. Apple's iPhone runs the iOS, and BlackBerry smartphones run the BlackBerry OS. Other devices run Google's Android OS, HP's webOS, and Microsoft's Windows Phone.
While almost all cell phones include some sort of software (even the most basic models these days include an address book or some sort of contact manager, for example), a smartphone will have the ability to do more. It may allow you to create and edit Microsoft Office documents--or at least view the files. It may allow you to download apps, such as personal and business finance managers, handy personal assistants, or, well, almost anything. Or it may allow you to edit photos, get ]driving directions via GPS, and create a playlist of digital tunes.
More smartphones can access the Web at higher speeds, thanks to the growth of 4G and 3G data networks, as well as the addition of Wi-Fi support to many handsets. Still, while not all smartphones offer high-speed Web access, they all offer some sort of access. You can use your smartphone to browse your favorite sites.
By our definition, a smartphone includes a QWERTY keyboard. This means that the keys are laid out in the same manner they would be on your computer keyboard--not in alphabetical order on top of a numeric keypad, where you have to tap the number 1 to enter an A, B, or C. The keyboard can be hardware (physical keys that you type on) or software (on a touch screen, like you'll find on the iPhone).
All cell phones can send and receive text messages, but what sets a smartphone apart is its handling of e-mail. A smartphone can sync with your personal and, most likely, your professional e-mail account. Some smartphones can support multiple e-mail accounts. Others include access to the popular instant messaging services, like AOL's AIM and Yahoo! Messenger.
These are just some of the features that make a smartphone smart. The technology surrounding smartphones and cell phones is constantly changing, though. What constitutes a smartphone today may change by next week, next month, or next year. Stay tuned!
Domain names are used to identify one or more IP addresses. For example, the domain name microsoft.com represents about a dozen IP addresses. Domain names are used in URLs to identify particular Web pages. For example, in the URL http://www.google.com/index.html, the domain name is google.com.
Every domain name has a suffix that indicates which top level domain (TLD) it belongs to. There are only a limited number of such domains. For example:
gov - Government agenciesBecause the Internet is based on IP addresses, not domain names, every Web server requires a Domain Name System (DNS) server to translate domain names into IP addresses.
edu - Educational institutions
org - Organizations (nonprofit)
mil - Military
com - commercial business
net - Network organizations
ca - Canada
th - Thailand
A typical server "rack" commonly seen in colocation centres
Internet hosting services can run Web servers. The scope of web hosting services varies greatly.
Smaller hosting services
The most basic is web page and small-scale file hosting, where files can be uploaded via File Transfer Protocol (FTP) or a Web interface. The files are usually delivered to the Web "as is" or with minimal processing. Many Internet service providers (ISPs) offer this service free to subscribers. Individuals and organizations may also obtain Web page hosting from alternative service providers.
Free web hosting service is offered by different companies with limited services, sometimes supported by advertisements, and often limited when compared to paid hosting.
Single page hosting is generally sufficient for personal web pages. Personal web site hosting is typically free, advertisement-sponsored, or inexpensive. Business web site hosting often has a higher expense depending upon the size and type of the site.
Larger hosting services
Many large companies that are not Internet service providers need to be permanently connected to the web to send email, files, etc. to other sites. The company may use the computer as a website host to provide details of their goods and services and facilities for online orders.
A complex site calls for a more comprehensive package that provides database support and application development platforms (e.g. ASP.NET, ColdFusion, Java EE, Perl/Plack, PHP or Ruby on Rails). These facilities allow customers to write or install scripts for applications like forums and content management. Also, Secure Sockets Layer (SSL) is typically used for websites that wish to keep the data transmitted more secure.
Shared web hosting service: one's website is placed on the same server as many other sites, ranging from a few sites to hundreds of websites. Typically, all domains may share a common pool of server resources, such as RAM and the CPU. The features available with this type of service can be quite basic and not flexible in terms of software and updates. Resellers often sell shared web hosting and web companies often have reseller accounts to provide hosting for clients.
Reseller web hosting: allows clients to become web hosts themselves. Resellers could function, for individual domains, under any combination of these listed types of hosting, depending on who they are affiliated with as a reseller. Resellers' accounts may vary tremendously in size: they may have their own virtual dedicated server to a colocated server. Many resellers provide a nearly identical service to their provider's shared hosting plan and provide the technical support themselves.
Virtual Dedicated Server: also known as a Virtual Private Server (VPS), divides server resources into virtual servers, where resources can be allocated in a way that does not directly reflect the underlying hardware. VPS will often be allocated resources based on a one server to many VPSs relationship, however virtualisation may be done for a number of reasons, including the ability to move a VPS container between servers. The users may have root access to their own virtual space. Customers are sometimes responsible for patching and maintaining the server (unmanaged server) or the VPS provider may provide server admin tasks for the customer (managed server).
Dedicated hosting service: the user gets his or her own Web server and gains full control over it (user has root access for Linux/administrator access for Windows); however, the user typically does not own the server. One type of dedicated hosting is self-managed or unmanaged. This is usually the least expensive for dedicated plans. The user has full administrative access to the server, which means the client is responsible for the security and maintenance of his own dedicated server.
Managed hosting service: the user gets his or her own Web server but is not allowed full control over it (user is denied root access for Linux/administrator access for Windows); however, they are allowed to manage their data via FTP or other remote management tools. The user is disallowed full control so that the provider can guarantee quality of service by not allowing the user to modify the server or potentially create configuration problems. The user typically does not own the server. The server is leased to the client.
Colocation web hosting service: similar to the dedicated web hosting service, but the user owns the colo server; the hosting company provides physical space that the server takes up and takes care of the server. This is the most powerful and expensive type of web hosting service. In most cases, the colocation provider may provide little to no support directly for their client's machine, providing only the electrical, Internet access, and storage facilities for the server. In most cases for colo, the client would have his own administrator visit the data center on site to do any hardware upgrades or changes. Formerly, many colocation providers would accept any system configuration for hosting, even ones housed in desktop-style minitower cases, but most hosts now require rack mount enclosures and standard system configurations.
Cloud hosting: is a new type of hosting platform that allows customers powerful, scalable and reliable hosting based on clustered load-balanced servers and utility billing. A cloud hosted website may be more reliable than alternatives since other computers in the cloud can compensate when a single piece of hardware goes down. Also, local power disruptions or even natural disasters are less problematic for cloud hosted sites, as cloud hosting is decentralized. Cloud hosting also allows providers to charge users only for resources consumed by the user, rather than a flat fee for the amount the user expects they will use, or a fixed cost upfront hardware investment. Alternatively, the lack of centralization may give users less control on where their data is located which could be a problem for users with data security or privacy concerns.
Clustered hosting: having multiple servers hosting the same content for better resource utilization. Clustered servers are a perfect solution for high-availability dedicated hosting, or creating a scalable web hosting solution. A cluster may separate web serving from database hosting capability. (Usually web hosts use clustered hosting for their shared hosting plans, as there are multiple benefits to the mass managing of clients).
Grid hosting: this form of distributed hosting is when a server cluster acts like a grid and is composed of multiple nodes.
Home server: usually a single machine placed in a private residence can be used to host one or more web sites from a usually consumer-grade broadband connection. These can be purpose-built machines or more commonly old PCs. Some ISPs actively attempt to block home servers by disallowing incoming requests to TCP port 80 of the user's connection and by refusing to provide static IP addresses. A common way to attain a reliable DNS host name is by creating an account with a dynamic DNS service. A dynamic DNS service will automatically change the IP address that a URL points to when the IP address changes.
A VPS runs its own copy of an operating system, and customers have superuser-level access to that operating system instance, so they can install almost any software that runs on that OS. For many purposes they are functionally equivalent to a dedicated physical server, and being software-defined, are able to be much more easily created and configured. They are priced much lower than an equivalent physical server, but as they share the underlying physical hardware with other VPSs, performance may be lower, and may depend on the workload of other instances on the same hardware node.
3 Cloud servers
4 See also
The force driving server virtualization is similar to that which led to the development of time-sharing and multiprogramming in the past. Although the resources are still shared, as under the time-sharing model, virtualization provides a higher level of security, dependent on the type of virtualization used, as the individual virtual servers are mostly isolated from each other and may run their own full-fledged operating system which can be independently rebooted as a virtual instance.
Partitioning a single server to appear as multiple servers has been increasingly common on microcomputers since the launch of VMware ESX Server in 2001. The physical server typically runs a hypervisor which is tasked with creating, releasing, and managing the resources of "guest" operating systems, or virtual machines.
These guest operating systems are allocated a share of resources of the physical server, typically in a manner in which the guest is not aware of any other physical resources save for those allocated to it by the hypervisor. As a VPS runs its own copy of its operating system, customers have superuser-level access to that operating system instance, and can install almost any software that runs on the OS; however, due to the number of virtualization clients typically running on a single machine, a VPS generally has limited processor time, RAM, and disk space.
Although VMware and Hyper-V dominate in-house corporate virtualization, because of their cost and limitations they are less common for VPS providers, which instead typically use products such as OpenVZ, Virtuozzo, Xen or KVM
Main article: Comparison of platform virtualization software
Many companies offer virtual private server hosting or virtual dedicated server hosting as an extension for web hosting services. There are several challenges to consider when licensing proprietary software in multi-tenant virtual environments.
With unmanaged or self-managed hosting, the customer is left to administer his own server instance.
Unmetered hosting is generally offered with no limit on the amount of data-transferred on a fixed bandwidth line. Usually, unmetered hosting is offered with 10 Mbit/s, 100 Mbit/s or 1000 Mbit/s (with some as high as 10Gbit/s). This means that the customer is theoretically able to use ~3 TB on 10 Mbit/s or up to ~300 TB on a 1000 Mbit/s line per month, although in practice the values will be significantly less.
In a virtual private server, this will be shared bandwidth and a fair usage policy should be involved. Unlimited hosting is also commonly marketed but generally limited by acceptable usage policies and terms of service. Offers of unlimited disk space and bandwidth are always false due to cost, carrier capacities and technological boundaries.
Main article: Cloud computing
A VPS which is dynamic (that is, it can be changed at runtime) is often referred to as a cloud server.
Key attributes for this are:
Infrastructure as Code defines the 'physical' services to be provided through a software definition
Additional hardware resources (CPU, RAM) can be added on request
Additional servers can be brought on line and added to a shared or load balanced pool dynamically. (Automatically according to load in some cases.)
Remote Desktop Protocol
Virtual Private Network