There are several different kinds of connectivity. The most basic level is through file system compatibility and the ability to share files through removable or fixed media. A more recent kind of connectivity is through various network protocols, especially through TCP/IP (and the internet). The ability to share files, data, and messages through a network was the original motivation for networks. The ability to share web pages, movies, animations, games, sounds, music, and other media through a network has driven widespread home use of computers and internet aware devices. The ability to move money through networks predates computers. Closely related to connectivity is the ability to share software, either by serving applications over a network or the internet or by emulation.
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connection methods
Inter-OS Communications
Mail Systems
Data Base Systems
Distributed Processing
Serving Applications
Cross Platform Emulation
mixed OS operations
manufacturer comments
related web sites
There are two basic methods for computers to connect to each other: (1) server/client and (2) peer-to-peer.
In a server/client network, one computer acts as the server and is in charge of the connection, while the other computer acts as a client and makes requests of the server. This is the classic approach for the internet. HTTP (web serving) and FTP (file serving) are handled in a server/client approach. It is possible for a single physical computer to act as a server in relationship with some computers and simultaneously act as a client with other computers (or even for a pair of computers to each be server to the other's client in different transactions.
In a peer-to-peer network, two or more computers are equal level partners in communications between machines.
See also: File Systems
One measure of connectivity is the file systems that an operating system can read and write. In some cases, the access may be read only (to provide access to old information). Of course, the ability to interpret the contents of the files stored in a file system is generally left to application software.
Note that in general, you only care about the file systems in use by your organization and used on removeable media that you are likely to encounter. The most commonly encountered file systems on removeable media are: Windows NT (ntfs), MS-DOS (fat), Windows 95 (vfat and fat32), Macintosh (HFS and HFS+), and UNIX (UFS), as well as ISO 9660 on CD-ROMs. Otherwise, you main interest in file systems is the capabilities of the native file system of each operating system.
"The issue is not with physical readability of file system inserted into different computers, but with cross platform mounting and reading e.g. over a network. Nobody in his sane mind will use a FAT file system on a file server. NFS, which is largely modelled after the Unix file system, is however ubiquitous, and to a degree NTFS over SMB becomes so. There is however no decent file server that offers its services in HFS+ like format."
"Also, being able to read a particular file format is not the end of the trouble. Each system presents forks in a different way, and on most systems you will have trouble creating or updating a fork properly." —Ronald C.F. Antonye72
"Another disk related design flaw in the Microsoft suite of operating systems is its antiquated use of 'drive letters,' i.e. drive C:, drive D:, etc. This schema imposes hardware specific limitations on system administrators and users alike. This is highly inappropriate for client/server environments where network shares and file systems are to represent hierarchies meaningful to humans. UNIX allows shared network filesystems to be mounted at any point in a directory structure. A network share can also span multiple disk drives (or even different machines!) in UNIX, thus allowing administrators to maintain pre-existing directory structures that are well-known to users, yet allowing them to expand the available disk space on the server, making such system changes transparent to users. This single difference between the UNIX and Windows operating systems further underscores the original intentions of their respective designers: UNIX was conceived as a client/server operating system for professional use, whereas Windows and its descendents sprang from DOS, an operating system that was never intended to be a player in a client/server environment, much less a server. For more detailed information on this topic, see Nicholas Petreley's article It will take less drive to make most PC operating systems work like Unix" —John Kirsch, "Microsoft Windows NT Server 4.0 versus UNIX"w51
Another measure of connectivity is the ability to connect to a wide variety of computers with a wide variety of operating systems and application software in use.
Microsoft has been running a series of television commercials claiming that Windows 2000 can easily connect to other systems and that it is easy to merge operations on separate Windows 2000 systems. Windows 2000 is in fact unable to connect to any other operating system unless the other operating system provides the connectivity (UNIX, NetWare, and the Macintosh provide the ability to connect to Windows). Merging multiple Windows 2000 systems (even just two Windows 2000 systems) is a difficult and time consuming process subject to errors and loss of data. Some businesses have been unable to get a new Windows 2000 system to correctly run their business, even after more than a year of direct Microsoft support.
"What can you expect from Windows NT Server out of the box and from UNIX out of the box? NT can communicate with many different types of computers. So can UNIX. … Essentially, both operating systems meet the minimum requirements for operating systems functioning in a networked environment. Put briefly, UNIX can do anything that NT can do and more."—John Kirschw22
Related web site: ftp://ftp.eng.auburn.edu/pub/doug/ "bootp-DH2.x" free, patched CMU BOOTP-DD2.4.x server from Doug Hughes of auburn.edu. Supports DHCP, even for Win95 clients. Adds the patches from the Samba mailing list to support PCNFS and Win95 simultaneously. For SunOS 4.x, Solaris 2.x, Linux, and NetBSD servers.
Another measure of connectivity is file and print serving. File serving is when a machine (or machines) is used to store the files for other computers. Print serving is when a machine collects the items to be printed from many computers and organizes (queues) the print jobs to one or more printers. This allows sharing a very expensive or specialized or high speed printer among many computers. Many modern printers (especially expensive ones) are capable of connecting directly to some kinds of networks.
"Since Microsoft sees NT as a viable alternative to all other network-capable operating systems on the market, UNIX and Novell included, one would assume that NT would come with all the tools necessary to accomplish the most basic tasks required: file and printer services. Any systems/network administrator knows from experience that there are two important issues to be considered when setting up a file server or adding a new network user: security, i.e. passwords and file permissions; and quotas for limiting disk usage of any new or existing users or groups. Although NT provides basic password security, it only provides file-level security if you choose to use its proprietary filesystem called NTFS. More important than this issue, however, is that NT does not provide any mechanism for limiting a user's disk usage! UNIX and Novell, on the other hand, provide software for performing this seemingly elementary control." —John Kirsch, "Microsoft Windows NT Server 4.0 versus UNIX"w51
"Even companies that have routine file-and-print requirements are finding that NT Server isn't always competitive with more mature technologies. Bob Sachikiny, a VP with the Aberdeen Group, says a client recently evaluated replacing Novell NetWare with NT. But when company officials realized they would need five NT servers for every three NetWare servers, they decided to keep their Novell network." —"The Hidden Cost Of NT"w69
"To summarize, once you logon to an NT network, all you can do is read files and print. In a UNIX environment, once you log in to a UNIX server, you can be on that machine and do anything on it that you could do if you were sitting at its keyboard and mouse! With NT, don't plan on being able to set up an e-mail server with the software at hand. You will need to buy expensive mail server software like Microsoft Exchange Server separately. If your NT server should function as a file server — what else can you do with it really? — don't plan on being able to prevent users from crashing the server by filling up the disk(s) with their data." —John Kirsch, "Microsoft Windows NT Server 4.0 versus UNIX"w51
"Yesterday's college students learned their Unix expertise on Linux and FreeBSD. Today they're working in IT departments, and many of them are openly hostile to both Microsoft and Windows NT. As a result, Linux, BSD, Solaris, and other forms of Unix are finding their way into IT departments, both overtly and on the sly.
"For example, are you sure that's an NT server you're connecting to at work? IS employees in many corporations have secretly installed Unix servers that provide native NT services. Why take such a risk? Linux and FreeBSD are free, as is SAMBA, the software that provides NT services. So the IS department saves money. And managers are unlikely to find out Unix is behind the scenes because fewer people will complain about server downtime.
"Fewer people will complain because the servers are more stable than Windows NT. Linux, FreeBSD, and BSDI Unix outperform Windows NT by a wide margin on limited hardware, and under some circumstances can perform as well or better than NT on the best hardware. Once behind in scalability features, Unix on Intel is catching up and may soon surpass NT in the number of processors it can use, and how it uses them." —Nicholas Petreley, "The new Unix alters NT's orbit", NC Worldw74
Data base management systems are a more sophisticated method for handling data than simple file systems. A Data Base Management System (often abbreviated DBMS) is in many ways just a larger version of a spread sheet or a single user data base program. A data base management system stores data and provides a system for selected humans or programs to update or chage selected pieces of data, allow other selected humans or programs to read selected pieces of data, and usually provides methods for searching, sorting, comparing, and otherwise using or manipulating the stored data (including making charts and other graphic representations, as well as a wide variety of reports).
There have been many different data base management systems invented. Most modern systems support the Standard Query language (often abbreviated SQL), an international standard for communications between data base management systems and for handling transactions between a data base management system and either humans or programs making requests (reading, writing, or using information in the data base). SQL isolates users from the actual physical methods for storing information in any particular data base management system, allowing businesses and other organizations to interconnect widely divergent internal systems into a smooth operating whole. SQL was originally proposed by IBM, but Oracle was the first organization to have a working version. Oracle continues to be the high end data base management system of choice, but many of its capabilities (other than sheer speed when handling very high volumes of requests) are available in the free MySQL that can be installed on any version of UNIX (including Linux).
Mail Transport Agents
Another measure of connectivity is the ability to run internal and external e-mail systems.
"For most businesses, e-mail has become an indispensable tool for communication, and most companies run their own internal/external e-mail systems. With Windows NT, you will have to buy a separate software package in order to set up an e-mail server. UNIX operating systems come with a program called Sendmail. There are other mail server software packages (or MTAs, Mail Transport Agents) available for UNIX, but this one is the most widely used, and it is free. Some UNIX administrators feel that exim or qmail are better choices since they are not as difficult to configure as sendmail. Both exim and qmail, like sendmail as well, are free for use even in a commercial environment. Many NT-based companies use Microsoft Exchange Server as their MTA. This is an expensive solution with limited success in an enterprise environment. Microsoft Exchange Server Enterprise Edition — 25 Client Access Licenses costs $3,549.00. If you have more than 25 employees, the same package with 50 Client Access Licenses costs $4,859.00 (Source: Microsoft). For more information on this topic see http://www.unix-vs-nt.org/kirch/sendmail-exchange.html ֹMicrosoft Exchange versus Sendmail: Views of Other MIS Professionals'." —John Kirsch, "Microsoft Windows NT Server 4.0 versus UNIX"w51
See also: Internet Services
Internet connectivity has become essential for almost all operating systems.
"What is not trivial, however, is that a networked operating system [Windows NT] in this price range should ship without a telnet server, SMTP server (e-mail), disk quotas, news server, or at least a DNS server that works to customers' satisfaction (many NT administrators feel compelled to go with third party DNS solutions). In order to match the functionality of a BSDI installation, additional Microsoft products and third-party solutions would bring the final price of a comparable NT solution to around $4,000, according to BSDI white paper compare." —"Microsoft Windows NT Server 4.0 versus UNIX"w51
Distributed processing is closely related to multi-processing and involves sharing computations across loosely connected computers.
Parallel processing is the idea of breaking up a large computing process into small independent parts. Super computers were built to do this kind of work.
A special kind of parallel processing is the kind that involves problems that can broken into independent parts. Problems such as weather models and fluid dynamics are dependent, in that small changes in one area of the problem affect their neighbors (and maybe even eventually affect the entire model, the so-called "butterful effect".
Parellel processing problems that can be broken into independent parts are sometimes called massively parallel. These problems lend themselves to shared work over the internet. Special programs can be written and distributed that allow thousands or millions of individuals to donate spare CPU cycles to solving very large problems. The client programs work kind of like screen savers, running when the computer would otherwise be idle, and report their results back to the central computer organizing the project.
The following is a list of some of the massively parallel projects that you can donate spare CPU cycles to:
www.setiathome.ssl.berkeley.edu: search for extraterrestrial intelligence at home
If you know of any other non-profit massively parallel projects, please let me know.
"NT is often considered to be a 'multi-user' operating system, but this is very misleading. An NT server will validate an authorized user, but once the user is logged on to the NT network, all he/she can do is access files and printers. The NT user cannot just run any application on the NT server (in order to take advantage of the superior processing power of server hardware). An NT user can only run special applications that have been written in two pieces, i.e. client/server applications. When a user logs in to a UNIX server, he/she can then run any application (provided the user is authorized to do so), thus taking the processing load off his/her workstation. This also includes graphics-based applications since X-server software is standard issue on all UNIX operating systems."—John Kirsch, "Microsoft Windows NT Server 4.0 versus UNIX"w22
Another measure of connectivity is the ability to run programs from other operating systems in emulation. Emulated software runs more slowly than native software, but allows for easy trading of data and use of obscure programs available on a limited number of platforms. Hardware emulation can attain the same speed as the actual system being emulated and has the possible advantage of sharing some computer resources (sharing hard drives, sharing monitors, etc.) and maybe even the ability to copy and paste between systems or other levels of direct sharing, as well as saving desk space by requiring only one computer set-up to run multiple systems.
Operating systems that can emulate MS-DOS: Amiga (with third party software or hardware emulation), FreeBSDe104, Macintosh (with third party software Virtual PC or hardware emulation), Macintosh OS X (with third party Virtual PC or Apple and third party hardware emulation), Macintosh OS X Server (with third party Virtual PC or Apple and third party hardware emulation), OS/2 (built-in), Rhapsody (with third party Virtual PC running in the BlueBox)
Operating systems that can emulate Windows 3.1: Macintosh (with third party Virtual PC or Apple and third party hardware emulation), Macintosh OS X (with third party Virtual PC), OS/2 (built-in), Rhapsody (with third party Virtual PC running in the BlueBox)
Operating systems that can emulate Windows 95: AIX (with third party SoftWindows95)e101, Macintosh (with third party Virtual PC or SoftWindows95 or Apple and third party hardware emulation), Macintosh OS X (with third party Virtual PC or SoftWindows95), Rhapsody (with third party Virtual PC or SoftWindows95 running in the BlueBox), SCO OpenServer (with Merge)e119, SCO UNIXWare (with Merge)e119
Operating systems that can emulate Windows 98: Macintosh (with third party Virtual PC or SoftWindows98 or Apple and third party hardware emulation), Macintosh OS X (with third party Virtual PC or SoftWindows98), Rhapsody (with third party Virtual PC or SoftWindows98 running in the BlueBox)
Operating systems that can emulate Macintosh: Amiga (with third party hardware emulation)
Operating systems that can emulate LINUX: FreeBSDe104
Operating systems that can emulate SCO: FreeBSDe104
Operating systems that can emulate SVR4: FreeBSDe104
Operating systems that can emulate C64: Amiga (with third party software emulation)
Operating systems that can emulate Atari ST: Amiga (with third party software or hardware emulation)
"What is operating system emulation? Each computer family works with specifically tailored software, on the operating system level as well as on the application level. When you supply a computer with soft- and/or hardware so that it's able to use software written for a different platform, this is called emulation. The Amiga is sort of a world champion in emulating other platforms like the PC, Macintosh®, C64, Atari ST®, and more." —Amiga Emulationw44
Price listings are for courtesy purposes only and may be changed by the referenced businesses at any time without notice.
Virtual PC 3.0 with MS-DOS; Connectix; software that allows running MS-DOS software on a PowerPC Macintosh; $74.95
Virtual PC 3.0 with Windows 95; Connectix; software that allows running Windows 95 software on a PowerPC Macintosh; $144.95
Virtual PC 3.0 with Red Hat Linux; Connectix; software that allows running Linux software on a PowerPC Macintosh; Linux preconfigured on a software emulation of a Pentium machine, so there is no reformatting of hard drives or installation of Linux; both the Macintosh and Linux running simultaneously on the same computer; $84.95 ($34.95 after mail-in rebate)
Virtual PC for Windows 2000; Connectix; software that allows running Windows 2000 software on a PowerPC Macintosh; $239.95
"MCI has adopted a strategy of coexistence to address this issue. MCI runs NT Server in places where it's most appropriate—departmental and middle-tier application environments—while continuing to rely on hosts and Unix servers for high-transaction applications, says Craig Ashapa, MCI's senior manager for NT deployment. MCI's most important information resides on Digital VAX VMS servers, he adds. Ashapa acknowledges NT's limitations but works around them. The NT servers make up MCI's enabling architecture that lets desktop systems access the back-end servers. The NT domain architecture is set up so that if an NT server goes down, the desktop systems can still access the back-end servers. Homegrown failover software and hardware instantly moves work to the desktop systems if there's an outage." —"The Hidden Cost Of NT"w69
"Tippett Studio also uses NT in limited place. The computerized special-effects firm uses NT workstations, but has opted to remain with Unix servers because of the high availability, maturity, and manageability the platform offers. Tippett uses Silicon Graphics Irix servers. Despite the high upfront costs of these machines, they're more affordable than NT servers when support requirements are factored in, says Jeff Stringer, IS manager for Tippett. 'NT's not a true multiuser system,' adds Stringer. 'To adjust a file, I'd have to send someone to each desktop to shut them down while work commences on the server.' With the Irix systems, system administration chores can be conducted while the servers continue to process graphics files." —"The Hidden Cost Of NT"w69
The following is a list of interoperability guides. These can be used either for mixed OS operations or for assisting in the conversion from one OS to another.
AIX/HP-UX Interoperability Guide, Version 2: a detailed comparison of commands, OS calls, data structures, directories, and other parts of AIX and HP-UX, especially for those going from one OS to the other.
HP-UX/Sun Interoperability Cookbook: a detailed comparison of commands, OS calls, data structures, directories, and other parts of Sun-OS and HP-UX, especially for those going from one OS to the other.
SunOS to HP-UX 9.05 Porting Guide: a detailed comparison of commands, OS calls, data structures, directories, and other parts of Sun-OS and HP-UX, especially for those going from one OS to the other.
OS/2 Warp: "Connectivity for today's networked world."w27
"New hardware and software innovations make it easier than ever for Macintosh users to work with PCs running MS-DOS and Windows. With a Macintosh, you can read from and write to PC disks. You can share data over a network with PCs. You can run applications for MS-DOS and Windows, by using SoftWindows software from Insignia Solutions, by adding a DOS Compatibility Card to your Macintosh, or by purchasing one of the DOS Compatible Macintosh systems." — Apple Computersw49
Stokely's PC & Mac NFS, AppleShare, Unix Integration FAQ links
geek humor
"You are in a twisty little maze of standards, all conflicting." —Linas Vepstas
If a packet hits a pocket on a socket on a port,
And the bus is interrupted as a very last resort,
And the address of the memory makes your floppy disk abort,
Then the socket packet pocket has an error to report!
—networks, Dr Seuss style
Read details here.
A web site on dozens of operating systems simply can't be maintained by one person. This is a cooperative effort. If you spot an error in fact, grammar, syntax, or spelling, or a broken link, or have additional information, commentary, or constructive criticism, please e-mail Milo. If you have any extra copies of docs, manuals, or other materials that can assist in accuracy and completeness, please send them to Milo, PO Box 1361, Tustin, CA, USA, 92781.
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Copyright © 1998, 1999, 2000, 2001, 2004 Milo
Last Updated: April 4, 2004
Created: June 15, 1998