Case Study 3:Time-sharing and Multiprogramming System

          In 1950’s multiprogramming capabilities was developed as a feature of the operating system. Computer multiprogramming is the allocation of a computer system and its resources to more than one concurrent application, job or user. Time-sharing, on the other hand, refers to the concurrent use of a computer by more than one user -- users share the computer's time. Time sharing is synonymous with multi-user. Multi-user is common in internet cafes and the like.
          Time-sharing and multiprogramming systems have good uses but along with these uses are security problems. These problems may later lead to serious issues and threats. One of the most common problems in   time-sharing and multiprogramming system is stealing or copying a user’s file. A person can easily alter or even delete the contents of a certain file without an authorized access or permission from the owner of the file. These files may be important files and would lead to serious problems if changes are made. There are also files that are confidential to the owner and would lead to serious problems if exposed. This act can also be considered as plagiarism. Plagiarism is copying another's work, or borrowing someone else's original ideas and making them yours. For instance, copying the user’s compositions, writings, poems, and others and printing it with your name as the writer. It is an act that is prohibited by the law because that person who stole the file, stole the original ideas of the owner of the file.
Another problem is deleting, changing and installing programs or applications without proper authorization. For instance, in an internet café, you can easily install or delete an application on the computer without the owner or operator knowing it. The user of the computer can also change the contents of some programs. This may cause those programs not to function well. Installing programs to the computer could also be a problem. There is a tendency that the program or application that will be installed might carry viruses that can harm the system. These changes can also affect the other users of the system. It would also be a great burden for the owner to be fixing such problems.
         A dedicated machine is a computer that services one primary function or task. For example, an automobile might have an onboard computer that is dedicated solely to navigation. I can say that dedicated machines are more secured than the time-sharing machines. Base on the definition, a dedicated machine is a machine that is intended to perform a single certain task, thus it ensures that it only performs the tasks that are intended for it. Dedicated machines are also used by only one user. Therefore, using dedicated machines than time-sharing machines is more secure because in dedicated machines, the user or owner is the only person that can access the machine. This helps in preventing security problems like the ones mentioned above. And also in dedicated machines, the user is confident and secured that all his files and all the programs or applications installed in the machine are kept private and unauthorized access will be blocked.

Case Study 2:Hand-held Computers

          A computer is a device that computes, especially a programmable electronic machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information. If we trace the history of computers, we could see that one of the first computers that were used had a size that we could not imagine possible for a computer. As the time pass by, along with the growing knowledge of the human mind, major breakthroughs in the digital world were also made. Discoveries were made known and different devices were created. Computers evolved from what we called the mainframes, these are computers that are made up of thousands of vacuum tubes. Then the 1970’s mini computers which are smaller and are composed only of hundreds of vacuum tubes. After that there was a wide spread use of microprocessors in the 1980’s. And in the 1990’s, hand held devices were widely used throughout the world. What is a hand held computer? Base on the definition from searchmobilecomputing.com, a handheld computer is a computer that can conveniently be stored in a pocket and used while you're holding it. Today's handheld computers, which are also called personal digital assistants (PDAs), can be divided into those that accept handwriting as input and those with small keyboards.

          In communication Arts, Journalism, and Publishing, a newspaper reporter is a person who reports, especially one employed to gather news for a newspaper, news agency, or broadcasting organization. In their type of work, the use of handheld computer would be a really great help to them. One way that a hand held computer can help them is in recording. Newspaper reporters are always on the go to search for any event or happening that would be reporting. They would need to record everything that has happened in that event, and that record would later be edited. A traditional newspaper reporter would use a piece of paper and a pen to write down every detail of the event. It would be a disadvantage because it would take quite a lot of their time and their effort. And there is a tendency that they would miss a part of that event while they are writing. They would also need a place where they could write properly and it would be a disadvantage if they are in a fight scene or a scene that does not have that kind of place. By using hand held computers, newspaper reporters would have an efficient use of their time and effort. Hand held, from the word itself, you can use it with just a hand. They can use a hand held computer to record every detail of the event without even having the need to look at what they are typing on the computer. They would be confident that whatever they typed would still be legible. And unlike the use of pen and paper, they can use the hand held computer without having a proper place to write or record. So they can use it even if they are in a war. Another way that a hand held computer could help a newspaper reporter is in doing research. Their job also requires research. They would need a lot of reference materials just like books and of course, the web. Nowadays, people would say that the web is more reliable than the books. Their reason was because they have seen too many errors in the books, especially in text books which are used by students as a reference material. So, in doing their research, newspaper reporters would need an internet connection. Today, with the use of mobile phones, we can have an internet access. So internet connection is also made handy. Even if a newspaper reporter does not have a personal computer at home, he would not have the need to go to an internet café or a library to use a desktop computer. The only thing that he needs is his mobile phone, of course the modern mobile phones and not those with antennas. So anytime, anywhere ha can do his research.
          A general practitioner doctor is a physician whose practice is not oriented to a specific medical specialty but instead covers a variety of medical problems in patients of all ages. In their type of work, they would be meeting different people with different character. And for some purposes, a doctor would need a record of each of his patient. Every record is written in a piece of paper and is stored in a certain place. The problem with this is that there is a tendency that the record of a patient would get lost. The doctor meets quite a large number of patients so it also means a large number of records. It would be time consuming if the doctor would look for a certain record and go through a huge stack of papers. By using hand held computers, doctors would not go through this problem looking for a single record. They can use hand held computer for their patient’s record. The record of each patient will be stored in a file and will be saved in the computer. So the doctor would not have to worry about loosing a record of his patient. And in searching a record, the doctor would not have the need to go through each of the saved record; all he needs to do is to type the name of his patient and in just an instant, the record would show up. It is what modern technology can do—a handy record book. And just like newspaper reporters, doctors still have the need to do a research. So with the use of a hand held computer, they can do their research in any place they want and in any time.
           In conclusion, hand held computer would be a great help to newspaper reporters and a general practitioner doctor. When used properly, it would make a really great change to the world but when not properly utilized would cause a great destruction to human kind. We must remember that everything has its own advantage and disadvantages.

Case Study 1:Types of Operating Systems

Batch Systems: OS/2

OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 (PS/2)" line of second-generation personal computers.

OS/2 is compatible with DOS and Windows, which means that it can run all DOS and Windows programs. However, programs written specifically to run under OS/2 will not run under DOS or Windows.

Any real mode operating system could also be made to run using OS/2's virtual machine capabilities, subject to certain direct hardware access limitations.

Because OS/2 only ran the user-mode system components of Windows, it was not compatible with Windows device drivers (VxDs) and applications needing them.

Multiple Windows applications ran in a single Windows session, just as they would under native Windows. To achieve true isolation between Windows 3.x programs, OS/2 could run multiple copies of Windows in parallel. This approach required considerable system resources, especially memory.

Interactive Systems: UNIX

Unix operating systems are widely used in servers, workstations, and mobile devices. The Unix environment and the client–server program model were essential elements in the development of the Internet and the reshaping of computing as centered in networks rather than in individual computers. Unix was designed to be portable, multi-tasking and multi-user in a time-sharing configuration.

Unix systems are characterized by various concepts:

·         the use of plain text for storing data

 ·         a hierarchical file system

·         treating devices and certain types of inter-process communication(IPC) as files; and

·         the use of a large number of software tools, small programs that can be strung together through a command line interpreter using pipes, as opposed to using a single monolithic program that includes all of the same functionality.

These concepts are collectively known as the Unix philosophy.

Real-time: RT- Linux

RT-Linux is an operating system in which a small real-time kernel coexists with the Posix-like Linux kernel. The intention is to make use of the sophisticated services and highly optimized average case behaviour of a standard time-shared computer system while still permitting real-time functions to operate in a predictable and low-latency environment.

RT-Linux is both spartan and extensible in accord with two, somewhat contradictory design premises.

The first design premise is that the truly time constrained components of a real-time application are not compatible with dynamic resource allocation, complex synchronization, or anything else that introduces either hard to bound delays or significant overhead. The most widely used configuration of RT-Linux offers primitive tasks with only statically allocated memory, no address space protection, a simple fixed priority scheduler with no protection against impossible schedules, hard interrupt disabling and shared memory as the only synchronization primitives between real-time tasks, and a limited range of operations on the FIFO queues connecting real-time tasks to Linux processes. The environment is not really as austere as all that, however, because the rich collection of services provided by the non-real-time kernel are easily accessed by Linux user tasks. Non-real-time components of applications migrate to Linux. One area where we hope to be able to make particular use of this paradigm is in QOS, where it seems reasonable to factor applications into hard real-time components that collect or distribute time sensitive data, and Linux processes or threads that monitor data rates, negotiate for process time, and adjust algorithms.

The second design premise is that little is known about how real-time systems should be organized and the operating system should allow for great flexibility in such things as the characteristics of real-time tasks, communication, and synchronization. The kernel has been designed with replaceable modules wherever practical and the spartan environment described in the previous paragraph is easily "improved" (or "cluttered", depending on one's point of view). There are alternative scheduling modules, some contributed by the user community, to allow for EDF and rate-monotonic scheduling of tasks. There is a "semaphore module" and there is active development of a richer set of system services. Linux makes it possible for these services to be offered by loadable kernel modules so that the fundamental operation of the real-time kernel is run-time (although not real-time) reconfigurable. It is possible to develop a set of tasks under RT-Linux, test a system using a EDF schedule, unload the EDF scheduling module, load a rate monotonic scheduling module, and continue the test. It should eventually be possible to use a memory protected process model, to test different implementations of IPCs, and to otherwise tinker with the system until the right mix of services is found.

Hybrid: Sun386i (codenamed Roadrunner)

The Sun386i was a hybrid UNIX workstation/PC compatible computer system produced by Sun Microsystems, launched in 1988. It was based on the Intel80386 microprocessor but shared many features with the contemporary Sun-3 series systems.

It designed for stand-alone operation or for connection to networks.  It is a multi-user, multi-tasking system but is also capable of running many MS-DOS applications. There are three models - the 150, the 150X and the 250.

Embedded: Windows CE

Known officially as Windows Embedded Compact or Windows Embedded CE is an operating system developed by Microsoft for minimalistic computers and embedded systems. Windows CE is a distinct operating system and kernel, rather than a trimmed-down version of desktop Windows.

Windows CE is optimized for devices that have minimal storage—a Windows CE kernel may run in under a megabyte of memory. It has evolved into a component-based, embedded, real-time operating system.  It is no longer targeted solely at hand-held computers.

A distinctive feature of Windows CE compared to other Microsoft operating systems is that large parts of it are offered in source code form. First, source code was offered to several vendors, so they could adjust it to their hardware. Then products like Platform Builder (an integrated environment for Windows CE OS image creation and integration, or customized operating system designs based on CE) offered several components in source code form to the general public. However, a number of core components that do not need adaptation to specific hardware environments (other than the CPU family) are still distributed in binary only form.