Junos OS is the FreeBSD-based operating system used in Juniper Networks hardware routers. It is an operating system, used in Juniper's routing and security devices. Juniper offers a Software Development Kit to partners and customers to allow additional customization; the biggest competitor of Junos is Cisco Systems' IOS. Junos OS was branded as Juniper Junos, is referred to as Junos, though this is a general brand name of Juniper Networks, including other product lines such as Junos Fusion; some of the key benefits Junos OS include: Modular design: Every process and component in a Juniper network setup is shielded from every other. One module crashing will have no effect on the rest of the system. Single train compatibility: Every Juniper switch, router, or other product runs the same JUNOS system; the system is built for simple inter-operability across the system. Junos provides a single code base across most of Juniper's platforms. Juniper has issued a new release of Junos every 90 days since 1998.
Junos supports a variety of routing protocols. With the introduction of the SRX and J-series platforms, it supports "flow mode", which includes stateful firewalling, NAT, IPsec, its a flexible routing policy language, used for controlling route advertisements and path selection. Junos adheres to industry standards for routing and MPLS; the operating system supports high availability mechanisms that are not standard to Unix, such as Graceful Restart. Junos operating system is based on Linux and FreeBSD, with Linux running as bare metal, FreeBSD running in a QEMU Virtual machine; because FreeBSD is a Unix implementation, customers can access a Unix shell and execute normal Unix commands. Junos runs on all Juniper hardware systems. After Juniper acquired NetScreen, it integrated ScreenOS security functions into its own Junos network operating system; the Junos CLI is a text-based command interface for configuring and monitoring the Juniper device and network traffic associated with it. It supports two types of command modes.
Operational Mode Configuration ModeThe functions of Operational Mode include control of the CLI environment, monitoring of hardware status, display of information about network data that passes though or into the hardware. The Configuration mode is used for configuring the Juniper router, switch, or security device, by adding, deleting, or modifying statements in the configuration hierarchy. Through the Juniper Developer Network Juniper Networks provides the Junos SDK to its customers and 3rd-party developers who want to develop applications for Junos-powered devices such as Juniper Networks routers and service gateway systems, it provides a set of tools and application programming interfaces, including interfaces to Junos routing, firewall filter, UI and traffic services functions. Juniper Networks employs the Junos SDK internally to develop parts of Junos and many Junos applications such as OpenFlow for Junos, other traffic services; as of 2016, Juniper maintains a market share in Ethernet Switching of 16.9% and a market share in Enterprise Routing of 16.1%.
Juniper generated a $2,353 million revenue in Routing, $858 million in Switching, $318 million in Security during 2016. Most of Juniper's revenue stems from The Americas, with Europe, Middle East, Africa, Asia combining for the rest of their annual revenue as of 2016. Official website Juniper Networks to Use Oracle Berkeley DB in JUNOS Software
In computing, a server is a computer program or a device that provides functionality for other programs or devices, called "clients". This architecture is called the client–server model, a single overall computation is distributed across multiple processes or devices. Servers can provide various functionalities called "services", such as sharing data or resources among multiple clients, or performing computation for a client. A single server can serve multiple clients, a single client can use multiple servers. A client process may run on the same device or may connect over a network to a server on a different device. Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, application servers. Client–server systems are today most implemented by the request–response model: a client sends a request to the server, which performs some action and sends a response back to the client with a result or acknowledgement. Designating a computer as "server-class hardware" implies that it is specialized for running servers on it.
This implies that it is more powerful and reliable than standard personal computers, but alternatively, large computing clusters may be composed of many simple, replaceable server components. The use of the word server in computing comes from queueing theory, where it dates to the mid 20th century, being notably used in Kendall, the paper that introduced Kendall's notation. In earlier papers, such as the Erlang, more concrete terms such as " operators" are used. In computing, "server" dates at least to RFC 5, one of the earliest documents describing ARPANET, is contrasted with "user", distinguishing two types of host: "server-host" and "user-host"; the use of "serving" dates to early documents, such as RFC 4, contrasting "serving-host" with "using-host". The Jargon File defines "server" in the common sense of a process performing service for requests remote, with the 1981 version reading: SERVER n. A kind of DAEMON which performs a service for the requester, which runs on a computer other than the one on which the server runs.
Speaking, the term server refers to a computer program or process. Through metonymy, it refers to a device used for running several server programs. On a network, such a device is called a host. In addition to server, the words serve and service are used, though servicer and servant are not; the word service may refer to either the abstract form of e.g. Web service. Alternatively, it may refer to a computer program that turns a computer into a server, e.g. Windows service. Used as "servers serve users", in the sense of "obey", today one says that "servers serve data", in the same sense as "give". For instance, web servers "serve web pages to users" or "service their requests"; the server is part of the client–server model. The nature of communication between a client and server is response; this is in contrast with peer-to-peer model. In principle, any computerized process that can be used or called by another process is a server, the calling process or processes is a client, thus any general purpose computer connected to a network can host servers.
For example, if files on a device are shared by some process, that process is a file server. Web server software can run on any capable computer, so a laptop or a personal computer can host a web server. While request–response is the most common client–server design, there are others, such as the publish–subscribe pattern. In the publish–subscribe pattern, clients register with a pub–sub server, subscribing to specified types of messages. Thereafter, the pub–sub server forwards matching messages to the clients without any further requests: the server pushes messages to the client, rather than the client pulling messages from the server as in request–response; the purpose of a server is to share data as well as to distribute work. A server computer can serve its own computer programs as well; the following table shows several scenarios. The entire structure of the Internet is based upon a client–server model. High-level root nameservers, DNS, routers direct the traffic on the internet. There are millions of servers connected to the Internet, running continuously throughout the world and every action taken by an ordinary Internet user requires one or more interactions with one or more server.
There are exceptions. Hardware requirement for servers vary depending on the server's purpose and its software. Since servers are accessed over a network, many run unattended without a computer monitor or input device, audio hardware and USB interfaces. Many servers do not have a graphical user interface, they are managed remotely. Remote management can be conducted via various methods including Microsoft Management Console, PowerShell, SSH and browser-based out-of-band management systems such as Dell's iDRAC or HP's iLo. Large traditional single servers would need to be run for long periods without interruption. Ava
In computing, a directory is a file system cataloging structure which contains references to other computer files, other directories. On many computers, directories are known as folders, or drawers, analogous to a workbench or the traditional office filing cabinet. Files are organized by storing related files in the same directory. In a hierarchical file system, a directory contained inside another directory is called a subdirectory; the terms parent and child are used to describe the relationship between a subdirectory and the directory in which it is cataloged, the latter being the parent. The top-most directory in such a filesystem, which does not have a parent of its own, is called the root directory, and on some modern embedded systems, the file systems either had no support for directories at all, or only had a "flat" directory structure, meaning subdirectories were not supported. In modern systems, a directory can contain a mix of subdirectories. A reference to a location in a directory system is called a path.
In many operating systems, programs have an associated working directory. File names accessed by the program are assumed to reside within this directory if the file names are not specified with an explicit directory name; some operating systems restrict a user's access to only their home directory or project directory, thus isolating their activities from all other users. In early versions of Unix the root directory was the home directory of the root user, but modern Unix uses another directory such as /root for this purpose. In keeping with Unix philosophy, Unix systems treat directories as a type of file; the name folder, presenting an analogy to the file folder used in offices, used in a hierarchical file system design for the Electronic Recording Machine, Accounting Mark 1 published in 1958 as well as by Xerox Star, is used in all modern operating systems' desktop environments. Folders are depicted with icons which visually resemble physical file folders. There is a difference between a directory, a file system concept, the graphical user interface metaphor, used to represent it.
For example, Microsoft Windows uses the concept of special folders to help present the contents of the computer to the user in a consistent way that frees the user from having to deal with absolute directory paths, which can vary between versions of Windows, between individual installations. Many operating systems have the concept of "smart folders" or virtual folders that reflect the results of a file system search or other operation; these folders do not represent a directory in the file hierarchy. Many email clients allow the creation of folders to organize email; these folders have no corresponding representation in the filesystem structure. If one is referring to a container of documents, the term folder is more appropriate; the term directory refers to the way a structured list of document files and folders is stored on the computer. The distinction can be due to the way. Operating systems that support hierarchical filesystems implement a form of caching to RAM of recent path lookups. In the Unix world, this is called Directory Name Lookup Cache, although it is called dcache on Linux.
For local filesystems, DNLC entries expire only under pressure from other more recent entries. For network file systems a coherence mechanism is necessary to ensure that entries have not been invalidated by other clients. Definition of directory by The Linux Information Project
A CD-ROM is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of read-only memory. During the 1990s, CD-ROMs were popularly used to distribute software and data for computers and fourth generation video game consoles; some CDs, called enhanced CDs, hold both computer data and audio with the latter capable of being played on a CD player, while data is only usable on a computer. The CD-ROM format was developed by Japanese company Denon in 1982, it was an extension of Compact Disc Digital Audio, adapted the format to hold any form of digital data, with a storage capacity of 553 MiB. CD-ROM was introduced by Denon and Sony at a Japanese computer show in 1984; the Yellow Book is the technical standard. One of a set of color-bound books that contain the technical specifications for all CD formats, the Yellow Book, standardized by Sony and Philips in 1983, specifies a format for discs with a maximum capacity of 650 MiB. CD-ROMs are identical in appearance to audio CDs, data are stored and retrieved in a similar manner.
Discs are made from a 1.2 mm thick disc of polycarbonate plastic, with a thin layer of aluminium to make a reflective surface. The most common size of CD-ROM is 120 mm in diameter, though the smaller Mini CD standard with an 80 mm diameter, as well as shaped compact discs in numerous non-standard sizes and molds, are available. Data is stored on the disc as a series of microscopic indentations. A laser is shone onto the reflective surface of the disc to read the pattern of lands; because the depth of the pits is one-quarter to one-sixth of the wavelength of the laser light used to read the disc, the reflected beam's phase is shifted in relation to the incoming beam, causing destructive interference and reducing the reflected beam's intensity. This is converted into binary data. Several formats are used for data stored on compact discs, known as the Rainbow Books; the Yellow Book, published in 1988, defines the specifications for CD-ROMs, standardized in 1989 as the ISO/IEC 10149 / ECMA-130 standard.
The CD-ROM standard builds on top of the original Red Book CD-DA standard for CD audio. Other standards, such as the White Book for Video CDs, further define formats based on the CD-ROM specifications; the Yellow Book itself is not available, but the standards with the corresponding content can be downloaded for free from ISO or ECMA. There are several standards that define how to structure data files on a CD-ROM. ISO 9660 defines the standard file system for a CD-ROM. ISO 13490 is an improvement on this standard which adds support for non-sequential write-once and re-writeable discs such as CD-R and CD-RW, as well as multiple sessions; the ISO 13346 standard was designed to address most of the shortcomings of ISO 9660, a subset of it evolved into the UDF format, adopted for DVDs. The bootable CD specification was issued in January 1995, to make a CD emulate a hard disk or floppy disk, is called El Torito. Data stored on CD-ROMs follows the standard CD data encoding techniques described in the Red Book specification.
This includes cross-interleaved Reed–Solomon coding, eight-to-fourteen modulation, the use of pits and lands for coding the bits into the physical surface of the CD. The structures used to group data on a CD-ROM are derived from the Red Book. Like audio CDs, a CD-ROM sector contains 2,352 bytes of user data, composed of 98 frames, each consisting of 33-bytes. Unlike audio CDs, the data stored in these sectors corresponds to any type of digital data, not audio samples encoded according to the audio CD specification. To structure and protect this data, the CD-ROM standard further defines two sector modes, Mode 1 and Mode 2, which describe two different layouts for the data inside a sector. A track inside a CD-ROM only contains sectors in the same mode, but if multiple tracks are present in a CD-ROM, each track can have its sectors in a different mode from the rest of the tracks, they can coexist with audio CD tracks as well, the case of mixed mode CDs. Both Mode 1 and 2 sectors use the first 16 bytes for header information, but differ in the remaining 2,336 bytes due to the use of error correction bytes.
Unlike an audio CD, a CD-ROM cannot rely on error concealment by interpolation. To achieve improved error correction and detection, Mode 1, used for digital data, adds a 32-bit cyclic redundancy check code for error detection, a third layer of Reed–Solomon error correction using a Reed-Solomon Product-like Code. Mode 1 therefore contains 288 bytes per sector for error detection and correction, leaving 2,048 bytes per sector available for data. Mode 2, more appropriate for image or video data, contains no additional error detection or correction bytes, having therefore 2,336 available data bytes per sector. Note that both modes, like audio CDs, still benefit from the lower layers of error correction at the frame level. Before being stored on a disc with the techniques described above, each CD-ROM sector is scrambled to prevent some problematic patterns from showing up; these scrambled sectors follow the same encoding process described in the Red Book in order to be stored
MS-DOS is an operating system for x86-based personal computers developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, some operating systems attempting to be compatible with MS-DOS, are sometimes referred to as "DOS". MS-DOS was the main operating system for IBM PC compatible personal computers during the 1980s and the early 1990s, when it was superseded by operating systems offering a graphical user interface, in various generations of the graphical Microsoft Windows operating system. MS-DOS was the result of the language developed in the seventies, used by IBM for its mainframe operating system. Microsoft acquired the rights to meet IBM specifications. IBM re-released it on August 12, 1981 as PC DOS 1.0 for use in their PCs. Although MS-DOS and PC DOS were developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility and capabilities. During its lifetime, several competing products were released for the x86 platform, MS-DOS went through eight versions, until development ceased in 2000.
MS-DOS was targeted at Intel 8086 processors running on computer hardware using floppy disks to store and access not only the operating system, but application software and user data as well. Progressive version releases delivered support for other mass storage media in greater sizes and formats, along with added feature support for newer processors and evolving computer architectures, it was the key product in Microsoft's growth from a programming language company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was the underlying basic operating system on which early versions of Windows ran as a GUI, it is a flexible operating system, consumes negligible installation space. MS-DOS was a renamed form of 86-DOS – owned by Seattle Computer Products, written by Tim Paterson. Development of 86-DOS took only six weeks, as it was a clone of Digital Research's CP/M, ported to run on 8086 processors and with two notable differences compared to CP/M.
This first version was shipped in August 1980. Microsoft, which needed an operating system for the IBM Personal Computer hired Tim Paterson in May 1981 and bought 86-DOS 1.10 for $75,000 in July of the same year. Microsoft kept the version number, but renamed it MS-DOS, they licensed MS-DOS 1.10/1.14 to IBM, who, in August 1981, offered it as PC DOS 1.0 as one of three operating systems for the IBM 5150, or the IBM PC. Within a year Microsoft licensed MS-DOS to over 70 other companies, it was designed to be an OS. Each computer would have its own distinct hardware and its own version of MS-DOS, similar to the situation that existed for CP/M, with MS-DOS emulating the same solution as CP/M to adapt for different hardware platforms. To this end, MS-DOS was designed with a modular structure with internal device drivers, minimally for primary disk drives and the console, integrated with the kernel and loaded by the boot loader, installable device drivers for other devices loaded and integrated at boot time.
The OEM would use a development kit provided by Microsoft to build a version of MS-DOS with their basic I/O drivers and a standard Microsoft kernel, which they would supply on disk to end users along with the hardware. Thus, there were many different versions of "MS-DOS" for different hardware, there is a major distinction between an IBM-compatible machine and an MS-DOS machine; some machines, like the Tandy 2000, were MS-DOS compatible but not IBM-compatible, so they could run software written for MS-DOS without dependence on the peripheral hardware of the IBM PC architecture. This design would have worked well for compatibility, if application programs had only used MS-DOS services to perform device I/O, indeed the same design philosophy is embodied in Windows NT. However, in MS-DOS's early days, the greater speed attainable by programs through direct control of hardware was of particular importance for games, which pushed the limits of their contemporary hardware. Soon an IBM-compatible architecture became the goal, before long all 8086-family computers emulated IBM's hardware, only a single version of MS-DOS for a fixed hardware platform was needed for the market.
This version is the version of MS-DOS, discussed here, as the dozens of other OEM versions of "MS-DOS" were only relevant to the systems they were designed for, in any case were similar in function and capability to some standard version for the IBM PC—often the same-numbered version, but not always, since some OEMs used their own proprietary version numbering schemes —with a few notable exceptions. Microsoft omitted multi-user support from MS-DOS because Microsoft's Unix-based operating system, was multi-user; the company planned, over time, to improve MS-DOS so it would be indistinguishable from single-user Xenix, or XEDOS, which would run on the Motorola 68000, Zilog Z8000, the LSI-11. Microsoft advertised MS-DOS and Xenix together, listing the shared features of its "single-user OS" and "the multi-user, multi-tasking, UNIX-derived operating system", promising easy
History of the Berkeley Software Distribution
The History of the Berkeley Software Distribution begins in the 1970s. The earliest distributions of Unix from Bell Labs in the 1970s included the source code to the operating system, allowing researchers at universities to modify and extend Unix; the operating system arrived at Berkeley in 1974, at the request of computer science professor Bob Fabry, on the program committee for the Symposium on Operating Systems Principles where Unix was first presented. A PDP-11/45 was bought to run the system, but for budgetary reasons, this machine was shared with the mathematics and statistics groups at Berkeley, who used RSTS, so that Unix only ran on the machine eight hours per day. A larger PDP-11/70 was installed at Berkeley the following year, using money from the Ingres database project. In 1975, Ken Thompson took a sabbatical from Bell Labs and came to Berkeley as a visiting professor, he started working on a Pascal implementation for the system. Graduate students Chuck Haley and Bill Joy improved Thompson's Pascal and implemented an improved text editor, ex.
Other universities became interested in the software at Berkeley, so in 1977 Joy started compiling the first Berkeley Software Distribution, released on March 9, 1978. 1BSD was an add-on to Version 6 Unix rather than a complete operating system in its own right. Some thirty copies were sent out; the Second Berkeley Software Distribution, released in May 1979, included updated versions of the 1BSD software as well as two new programs by Joy that persist on Unix systems to this day: the vi text editor and the C shell. Some 75 copies of 2BSD were sent out by Bill Joy. A further feature was a networking package called Berknet, developed by Eric Schmidt as part of his master's thesis work, that could connect up to twenty-six computers and provided email and file transfer. After 3BSD had come out for the VAX line of computers, new releases of 2BSD for the PDP-11 were still issued and distributed through USENIX. 2.9BSD from 1983 included code from 4.1cBSD, was the first release, a full OS rather than a set of applications and patches.
The most recent release, 2.11BSD, was first issued in 1992. In the 21st Century, maintenance updates from volunteers continued: patch 451 was released on December 22, 2018. A VAX computer was installed at Berkeley in 1978, but the port of Unix to the VAX architecture, UNIX/32V, did not take advantage of the VAX's virtual memory capabilities; the kernel of 32V was rewritten by Berkeley students to include a virtual memory implementation, a complete operating system including the new kernel, ports of the 2BSD utilities to the VAX, the utilities from 32V was released as 3BSD at the end of 1979. 3BSD was alternatively called Virtual VAX/UNIX or VMUNIX, BSD kernel images were called /vmunix until 4.4BSD. The success of 3BSD was a major factor in the Defense Advanced Research Projects Agency's decision to fund Berkeley's Computer Systems Research Group, which would develop a standard Unix platform for future DARPA research in the VLSI Project. 4BSD offered a number of enhancements over 3BSD, notably job control in the released csh, delivermail, "reliable" signals, the Curses programming library.
In a 1985 review of BSD releases, John Quarterman et al. wrote: 4BSD was the operating system of choice for VAXs from the beginning until the release of System III Most organizations would buy a 32V license and order 4BSD from Berkeley without bothering to get a 32V tape. Many installations inside the Bell System ran 4.1BSD. 4.1BSD was a response to criticisms of BSD's performance relative to the dominant VAX operating system, VMS. The 4.1BSD kernel was systematically tuned up by Bill Joy until it could perform as well as VMS on several benchmarks. The release would have been called 5BSD. Before its official release came three intermediate versions: 4.1a incorporated a modified version of BBN's preliminary TCP/IP implementation. Back at Bell Labs, 4.1cBSD became the basis of the 8th Edition of Research Unix, a commercially supported version was available from mtXinu. To guide the design of 4.2BSD, Duane Adams of DARPA formed a "steering committee" consisting of Bob Fabry, Bill Joy and Sam Leffler from UCB, Alan Nemeth and Rob Gurwitz from BBN, Dennis Ritchie from Bell Labs, Keith Lantz from Stanford, Rick Rashid from Carnegie-Mellon, Bert Halstead from MIT, Dan Lynch from ISI, Gerald J. Popek of UCLA.
The committee met from April 1981 to June 1983. Apart from the Fast File System, several features from outside contributors were accepted, including disk quotas and job control. Sun Microsystems provided testing on its Motorola 68000 machines prior to release, ensuring portability of the system; the official 4.2BSD release came in August 1983. It was notable as the first version released after the 1982 departure of Bill Joy to co-found Sun Microsystems.
Internet access is the ability of individuals and organizations to connect to the Internet using computer terminals and other devices. Internet access is sold by Internet service providers delivering connectivity at a wide range of data transfer rates via various networking technologies. Many organizations, including a growing number of municipal entities provide cost-free wireless access. Availability of Internet access was once limited, but has grown rapidly. In 1995, only 0.04 percent of the world's population had access, with well over half of those living in the United States, consumer use was through dial-up. By the first decade of the 21st century, many consumers in developed nations used faster broadband technology, by 2014, 41 percent of the world's population had access, broadband was ubiquitous worldwide, global average connection speeds exceeded one megabit per second; the Internet developed from the ARPANET, funded by the US government to support projects within the government and at universities and research laboratories in the US – but grew over time to include most of the world's large universities and the research arms of many technology companies.
Use by a wider audience only came in 1995 when restrictions on the use of the Internet to carry commercial traffic were lifted. In the early to mid-1980s, most Internet access was from personal computers and workstations directly connected to local area networks or from dial-up connections using modems and analog telephone lines. LANs operated at 10 Mbit/s, while modem data-rates grew from 1200 bit/s in the early 1980s, to 56 kbit/s by the late 1990s. Dial-up connections were made from terminals or computers running terminal emulation software to terminal servers on LANs; these dial-up connections did not support end-to-end use of the Internet protocols and only provided terminal to host connections. The introduction of network access servers supporting the Serial Line Internet Protocol and the point-to-point protocol extended the Internet protocols and made the full range of Internet services available to dial-up users. Broadband Internet access shortened to just broadband, is defined as "Internet access, always on, faster than the traditional dial-up access" and so covers a wide range of technologies.
Broadband connections are made using a computer's built in Ethernet networking capabilities, or by using a NIC expansion card. Most broadband services provide a continuous "always on" connection. Broadband provides improved access to Internet services such as: Faster world wide web browsing Faster downloading of documents, photographs and other large files Telephony, radio and videoconferencing Virtual private networks and remote system administration Online gaming massively multiplayer online role-playing games which are interaction-intensiveIn the 1990s, the National Information Infrastructure initiative in the U. S. made broadband Internet access a public policy issue. In 2000, most Internet access to homes was provided using dial-up, while many businesses and schools were using broadband connections. In 2000 there were just under 150 million dial-up subscriptions in the 34 OECD countries and fewer than 20 million broadband subscriptions. By 2004, broadband had grown and dial-up had declined so that the number of subscriptions were equal at 130 million each.
In 2010, in the OECD countries, over 90% of the Internet access subscriptions used broadband, broadband had grown to more than 300 million subscriptions, dial-up subscriptions had declined to fewer than 30 million. The broadband technologies in widest use are ADSL and cable Internet access. Newer technologies include VDSL and optical fibre extended closer to the subscriber in both telephone and cable plants. Fibre-optic communication, while only being used in premises and to the curb schemes, has played a crucial role in enabling broadband Internet access by making transmission of information at high data rates over longer distances much more cost-effective than copper wire technology. In areas not served by ADSL or cable, some community organizations and local governments are installing Wi-Fi networks. Wireless and satellite Internet are used in rural, undeveloped, or other hard to serve areas where wired Internet is not available. Newer technologies being deployed for fixed and mobile broadband access include WiMAX, LTE, fixed wireless, e.g. Motorola Canopy.
Starting in 2006, mobile broadband access is available at the consumer level using "3G" and "4G" technologies such as HSPA, EV-DO, HSPA+, LTE. In addition to access from home and the workplace Internet access may be available from public places such as libraries and Internet cafes, where computers with Internet connections are available; some libraries provide stations for physically connecting users' laptops to local area networks. Wireless Internet access points are available in public places such as airport halls, in some cases just for brief use while standing; some access points may provide coin-operated computers. Various terms are used, such as "public Internet kiosk", "public access terminal", "Web payphone". Many hotels have public terminals fee based. Coffee shops, shopping malls, other venues offer wireless access to computer networks, referred to as hotspots, for users who bring their own wireless-enabled devices such as a laptop or PDA; these services may be free to all, free to customer