{"id":168,"date":"2020-08-18T19:23:47","date_gmt":"2020-08-18T20:23:47","guid":{"rendered":"http:\/\/www.linux-tutorial.info\/?page_id=77"},"modified":"2020-08-22T19:26:41","modified_gmt":"2020-08-22T20:26:41","slug":"this-is-the-page-title-toplevel-2","status":"publish","type":"page","link":"http:\/\/www.linux-tutorial.info\/?page_id=168","title":{"rendered":"What Is an Operating System"},"content":{"rendered":"\nWhat Is an Operating System<\/title>\n<p>\nIn simple terms, an <glossary>operating system<\/glossary>\nis a manager. It manages all the available resources on a computer.\nThese resources can be the hard disk, a printer, or the monitor screen.\nEven memory is a resource that needs to be managed.\nWithin an operating system are the management functions that determine who gets to read data from\nthe hard disk, what file is going to be printed next, what characters appear on the screen, and so forth.\n<\/p>\n<p>\nIn addition to managing your hardware, the operating sytem also manages the <glossary>software<\/glossary>. It ensure programs are started correctly, that they do not conflict with each other and even how much memory a certain program gets.\n<\/p>\n<p>\nOnce upon a time, there was no such thing as an <glossary>operating system<\/glossary>.\nThe computers of forty years ago ran one program at a time. The computer programmer would load\nthe program he (they were almost universally male at that time) had written and run it. If there was\na mistake that caused the program to stop sooner than expected, the programmer had to start over.\nBecause there were many other people waiting for their turn to try their programs, it may have been\nseveral days before the first programmer got a chance to run his deck of cards through the machine\nagain. Even if the program did run correctly, the programmer probably never got to work on the\nmachine directly. The program (<glossary term=\"punch card\">punched cards<\/glossary>) was fed into the computer by an operator who then passed the printed output back to the programmer several hours later.\n<\/p>\n<p>\nAs technology advanced, many such programs, or jobs,\nwere all loaded onto a single tape. This tape was then loaded and manipulated by another program,\nwhich was the ancestor of today’s operating systems. This program would monitor the behavior of the\nrunning program and if it misbehaved (crashed), the monitor could then immediately load and run\nanother. Such programs were called (logically) monitors.\n<\/p>\n<p>\nIn the 1960’s, technology and <glossary>operating system<\/glossary>\ntheory advanced to the point that many different programs could be held in memory at once.\nThis was the concept of “multiprogramming.” If one program needed to wait for some external\n<glossary>event<\/glossary> such as the tape to rewind to the right spot, another program could have access to the <glossary>CPU<\/glossary>. This improved performance dramatically and allowed the CPU to be busy almost 100 percent of the time.\n<\/p>\n<p>\nBy the end of the 1960’s, something wonderful happened: <glossary>UNIX<\/glossary>\nwas born. It began as a one-man project designed by Ken Thompson of Bell Labs and has grown to become the most widely used <glossary>operating system<\/glossary>.\nIn the time since UNIX was first developed, it has gone through many different generations and even mutations. Some differ substantially from the original version, like BSD (Berkeley Software Distribution) UNIX or Linux. Others, still contain major portions that are based on the original\nsource code. (A friend of mine described UNIX as the only operating system where you can throw the manual onto the keyboard and get a real command.)\n<\/p>\n<p>\nLinux is an <glossary>operating system<\/glossary>\nlike many others, such as <glossary>DOS<\/glossary>,\nVMS, OS\/360, or CP\/M. It performs many of the same tasks in very similar manners. It is the\nmanager and administrator of all the system resources and facilities. Without\nit, nothing works. Despite this, most users can go on indefinitely without knowing even which\noperating system they are using, let alone the basics of how the operating system works.\n<\/p>\n<p>\nFor example, if you own a car, you don’t really need to know the details of the internal\ncombustion engine to understand that this is what makes the car move forward. You don’t need to know\nthe principles of hydraulics to understand what isn’t happening when pressing the brake pedal has no effect.\n<\/p>\n<p>\nAn <glossary>operating system<\/glossary>\nis like that. You can work productively for years without even knowing what operating system you’re\nrunning on, let alone how it works. Sometimes things go wrong. In many companies, you are given a\nnumber to call when problems arise, you report what happened, and it is dealt with.\n<\/p>\n<p>\nIf the computer is not back up within a few minutes, you get upset and call back, demanding to know when “that darned thing will be up and running again.” When the technician (or whoever has to deal with the problem) tries to explain what is happening and what is being done to correct the\nproblem, the response is usually along the lines of, “Well, I need it back up now.”\n<\/p>\n<p>\nThe problem is that many people hear the explanation, but don’t understand it. It is common for people to be unwilling to acknowledge that they didn’t understand the answer. Instead,\nthey try to deflect the other person’s attention away from that fact. Had they understood the explanation, they would be in a better position to understand what the technician is doing and that he\/she is actually working on the problem.\n<\/p>\n<p>\nBy having a working knowledge of the principles of an <glossary>operating system<\/glossary>\nyou are in a better position to understand not only the problems that can arise, but also what steps\nare necessary to find a solution. There is also the attitude that you have a better relationship\nwith things you understand. Like in a car, if you see steam pouring out from under the hood, you\nknow that you need to add water. This also applies to the operating system.\n<\/p>\n<p>\nIn this section, I am going to discuss what goes into an <glossary>operating system<\/glossary>,\nwhat it does, how it does it, and how you, the user, are affected by all this.\n<\/p>\n<question id=\"472\" text=\"What does the term 'multi-tasking' mean?\" \/>\n<question id=\"474\" text=\"Computers today typically execute transactions in what fraction of a second?\" \/>\n<p>\nBecause of advances in both hardware design and performance, computers are able to process\nincreasingly larger amounts of information. The speed at which computer transactions occur is often\ntalked about in terms of <em>billionths<\/em> of a second. Because of this speed, today’s computers\ncan give the appearance of doing many things simultaneously by actually switching back and forth\nbetween each task extremely fast. This is the concept of multitasking. That is, the computer is working on multiple tasks “at the same time.”\n<\/p>\n<question id=\"473\" text=\"What does the term 'multi-user' mean?\" \/>\n<question id=\"\" type=\"tf\" text=\"The term 'multi-user' means that the system has multiple accounts to allow different users to login.\" \/>\n<p>\nAnother function of the <glossary>operating system<\/glossary>\nis to keep track of what each program is doing. That is, the operating system needs to keep track of\nwhose program, or task, is currently writing its file to the printer or which program needs to read\na certain spot on the hard disk, etc. This is the concept of multi-users, as multiple users have\naccess to the same resources.\n<\/p>\n<p>\nIn subsequent sections, I will be referring to <glossary>UNIX<\/glossary>\nas an abstract entity. The concepts we will be discussing are the same for Linux and any other dialect. When necessary, I will specifically reference where Linux differs and try to mention where various Linux <glossary term=\"distribution\">distributions<\/glossary> differ.\n<\/p>\n<p>\nMost people are familiar with operating systems as something you load from a CD or DVD. In this cases, the operating system is referred to as software. However, there ware many cases where the operating system is built into the hardware. In fact, there are many devices that have Linux-based system built directly into the hardware. Thus the boundary between hardware and software is somewhat blurred. To simplify things one could say that although physically built into the hardware an operating system is still software\n<\/p>\n<question id=\"\" type=\"tf\" text=\"Software is always loaded\/installed from external media like a CD or tape.\" \/>\n<p>\nAnother kind of software are the services a computer provides. For example, the ability to send information to a printer is not usually considered part of the operating system, although it interacts directly with hardware. With operating system like Windows, these systems services are so integrated into the the operating system, the line between the two is almost invisible. With Linux it is very easy to swap out these components. For example, there are several different printing packages and which you choose to use is your choice and not that of the operating system vendor.\n<\/p>\n<p>\nThe next kind of software are applications. The provide a collection of functions for the benefit of the user (or perhaps the system administrator). A word processor or web browser do not interact directly with the hardware but use things like the system services, which then interact with the hardware. In both of these cases, the software is installed from CDs, files you download from the Internet and so forth. However, there are cases where application software existst solely within the hardware. For example, automatic teller machines have the application software built into the hardware although their functions it provides is still considered software.\n<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What Is an Operating System In simple terms, an operating system is a manager. It manages all the available resources on a computer. These resources can be the hard disk, a printer, or the monitor screen. Even memory is a … <a href=\"http:\/\/www.linux-tutorial.info\/?page_id=168\">Continue reading <span class=\"meta-nav\">→<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-168","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages\/168","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=168"}],"version-history":[{"count":1,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages\/168\/revisions"}],"predecessor-version":[{"id":791,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages\/168\/revisions\/791"}],"wp:attachment":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=168"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}