Sunday, February 27, 2011

Job and Process Status

Using the process state diagram, explain why there is no transition:

  • ·         From the READY to WAITING.
  • ·         From the WAITING to RUNNING.

We can somehow describe the flow of the diagram by identifying the specific duties of its “States” in the process management. When a particular job is formed it will be engaged in the “Hold State”. The “Holding” queue will then pass on a job scheduler before reaching the “Ready State”. The “Ready” queue will move to the “Running State”. The “Running” queue will be checked if there will be an interrupt or an I/O request. If there are, it will be brought to the “Waiting State”. “Waiting” queue will send signals to the “Ready State” to continue the process and it will be then process again. But if there are non, then the “Running” queue will proceed to another “Job Scheduler” before making into the “finished”. 
Transition is the process through which an existing circumstance, condition, or relationship (real or imagined) is acted on in a manner that produces a new and different circumstance or condition.

From the READY to WAITING.
            I will explain this particular situation by giving an appropriate example. Let just say that job X will be the one that will be process based on the diagram.
            When job X is in the “Ready State” it must first passed the job scheduler. The job scheduler will be the one that will allow a particular job (such as job X) to be process and move to the “Ready State”. The “Ready” queue will soon make use of the CPU (Central Processing Unit) then after that the particular job (job X) will be move on the “Running State” but remember not all job can successfully passed the “Running State” most likely an interrupt will appear. An interrupt on the “Running” queue will be issued on the “Ready State”.
 But if happen that the “Running” queue will be waiting for a device (such as an I/O request) in order to work it will eventually brought to the “Waiting State”. And that how a job processed from the “Ready” to “Waiting State”. As you can observe, no transition happen because the system has been divided on its specific duties in the process management which allows the operation of system to perform accountably.

            When job X is supposedly in the “Waiting State” it will release signals to the “Ready State” to continue the processing of the given job. The “Ready State” will recognize the signals and so the “Waiting” queue (job X) will be back then on the “Ready State”. This is because, all incoming jobs in system must go primarily into the “Ready state” and jobs can only enter the “Running state” by passing through the “Ready state”. Shifting directly from “Waiting” to “Running State” without passing through “Ready State” will cause error in the processing of jobs.
            When the “Ready” queue (job X) is set it will directly go to the “Running State”. The “Running” queue waits for any interrupt. If no interrupt or I/O request appears it will then go through another “Job Scheduler” before reaching the “Finished” which is the end of the process. Still no transition has been made because there is no manner that produces a new and different circumstance or condition in process management.   

Fixed Partition

Load the following jobs into memory using fixed partition following a certain memory allocation method (a. best-fit, b. first-fit, c. worst-fit).

Best Fit

First Fit

Worst Fit


Dynamic and Relocatable Partition

Dynamic Partition

Relocatable Dynamic Partition


Saturday, February 26, 2011

Security Problems with Multiprogramming and Time-Sharing Environments

In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems. Name at least two of these problems. Can we ensure the same degree of security in a time-share machine as we have in a dedicated machine? Explain your answer ...

1. Stealing or copying of other files

     This usually happen in multiprogramming and time-sharing environment, in most cases the user’s files (the original owner of the files) was being over written by other users. This dilemma will lead to stealing or copying of files which greatly affects many users and because of that it create a negative impact in all other users(who have their original files taken by others) to engage in a multiprogramming and time-sharing environment. They believe that once your file where found by other users they will directly copy it and even without your permission that is why most of the users were very vigilant when it comes to this particular machine. And also the ability of the virus to enter in a specific files which causes the files to be damage. In multiprogramming and time-sharing environment it usually happen because of the number of users which is actually connected to each other in which the virus easily transfer and spread from user to another, and if take for granted it may cause a lot more problems. But virus is easily detected by anti-computer virus so there is a small possibility that a virus can enter on your computer.

2. Using system resources (CPU, disk space) without proper accounting

     In a multiprogramming and time-sharing environment basically when the system resources such as CPU and disk space are not properly accounted it causes the printer to mix output by sending data while some other user's file is printing. This thing may result to scrambling of mix output which cases the users to have an unfamiliar data or output and most probably the user will find it difficult in compiling his/her mixed outputs again and that will lead him/her hard time in working with it.

Can we ensure the same degree of security in a time-share machine as we have in a dedicated machine?

Definitely no, why do I say so? Firstly, because in a time-sharing machine as what I have explained earlier it is not safe to use all files that you've worked for is not permanently secured and there is a tendency that it might be copied by other users when found.
            Secondly, it is virus prone. In most cases virus-spread is vulnerable most especially when there are lots of users on that time share machine. It may cause further damage on the files and other important programs if you don’t take it seriously. While in a dedicated machine not all files but most files were secured from being copied by other users and because it is dedicated machine it is not virus prone so there is no need to worry with regards to virus.
            And lastly, when we talk about the degree of security dedicated machine is more reliable because not all users can enter on it in return they don’t have the chance to change any files so it is applicable to anyone. Even though time-sharing machine is very helpful because you work with other users or other people but when it comes to the degree of security dedicated machines is much more reliable.

Wednesday, December 8, 2010

Handheld Computers

Hand held computers are  one of the most popular gadget in our modern world today. It not just help improving the modern technology but also the life of the people who use it.

A delivery person for a courier service

            Hand held computer are one of the most flexible, portable, and has many features device that can actually made your work much easier and take less effort.
            First, it is flexible. A delivery person can use this device anywhere and anytime by simply clicking it. It won’t take longer time in learning how to use this device because it is user friendly just like any other devices (such as cell phones).
            Secondly, it is portable. A delivery person can carry this device because it is unique design which can actually fit in your pocket. So there is no need for heavy and huge personal computers.
            Lastly, are its special features because of its special design feature such as map. It allows users to locate any place in the country which greatly help those delivery persons in locating their destination at no time.

Manager in a Supermarket

            Every now and then, we buy food to serve our family. We tend to have budget in buying all of these things for us to be able to survive most especially when there is a special occasion top celebrate. In a supermarket, there are employees and also what they call, “Boss.” It is because he or she manages and have the authority in making any forms of decisions with regards to what the employees should do that will results to a positive outcome in there customer services. But the question is, how?

            If the manager of a supermarket will use hand held computer the outcome of it will be the following:
            First, he or she will be updated to what is the latest price of the products they sell and purchase because hand held computer is similar to a minicomputer but a smaller version in which you can actually search and know the latest happenings not just in the country but also the world.
            Secondly, he or she may use it is as a file manager where he or she can put all important files with regards to business.
            Lastly, he or she will be able to list and count all the money that earned and spent by the supermarket because of the ability of the device to calculate any forms of businesses.

Thursday, November 25, 2010

Classification of Operating System

Below are the categories of Operating System:

  1. Batch Systems
      - batch system is one in which jobs are bundled together with the instructions necessary to allow them to be processed without intervention.
          OS :
      BOS/360 – (Basic Operating System) was an early IBM Operating System. According to folklore, BOS was the predecessor to TOS on the IBM 360 and it was IPL'd from a reader. It may have been intended for very small 360's with no disks and limited tape drives.BOS died out really early s disks such as the 2311 and 2314 became common with the IBM 360, whereas disks had been a real luxury on the IBM 7090.
  1. Interactive Systems
      - the user interacts directly with the operating system to supply commands and data as the application program executes and the user receives the results of processing immediately. The user is in direct two way communication with the computer.
      Interactive UNIX - A Unix-based operating system from Sun that runs on x86 machines. It has been widely used to connect character-based terminals or process control devices, such as bar code readers in a supermarket, to a central computer.
  1. Real-time Systems
      - A real-time OS has an advanced algorithm for scheduling. Scheduler flexibility enables a wider, computer-system orchestration of process priorities, but a real-time OS is more frequently dedicated to a narrow set of applications. Key factors in a real-time OS are minimal interrupt latency and minimal thread switching latency, but a real-time OS is valued more for how quickly or how predictably it can respond than for the amount of work it can perform in a given period of time.
      VxWorks - VxWorks is a real-time operating system made and sold by Wind River Systems of Alameda, California, USA. Intel acquired Wind River Systems on July 17, 2009. VxWorks is designed for use in embedded systems. Unlike "self-hosting" systems such as Unix, VxWorks development is done on a "host" machine running Linux, Unix, or Windows, cross-compiling target software to run on various "target" CPU architectures.
  1. Hybrid Systems
      - An HOS is a computer running the base operating system, and one or more OSs at the same time using a virtual machine.
      Blackberry OS 6 Hybrid - This OS 6 hybrid uses either a leaked or official OS depending on which device it’s being loaded on to. For the 9000, the OS 6 hybrid uses OS as base OS. In the end, you end up with a OS with the following:
  • East Asian Language support is included and fully functional.
  • Google Maps v4.2.0, UberTwitter v0.971, Twitter for BlackBerry v1.0.40, newest App World, FourSquare v1.8.4, and Xtreme Labs Speedtest are all included.
  • Includes all stock Blackberry games and IM Applications with loader options.
  • Includes an option to install the Mobile Launcher
      There are about 20 OS 6 files dropped into a 5.0 base build error free. Many of these are fairly useless files but there are some interesting updated files such as Search, which we know is very robust in OS 6 and might work on an OS 5 device with this hybrid. We’ll have to test more to see. Other than the OS 6 files, the build also uses files on for additional UI speed and the browser file from which ismuch faster than previous versions.
  1. Embedded Systems
      - An embedded system is a computer system designed to perform one or a few dedicated functions often with real computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal computer (PC), is designed to be flexible and to meet a wide range of end-user needs. Embedded systems control many devices in common use today.
      Tiny OS - is a free and open source component-based operating system and platform targeting wireless sensor networks (WSNs). TinyOS is an embedded operating system written in the nesC programming language as a set of cooperating tasks and processes. It is intended to be incorporated into smartdust. TinyOS started as a collaboration between the University of California, Berkeley in co-operation with Intel Research and Crossbow Technology, and has since grown to be an international consortium, the TinyOS Alliance.

Monday, November 22, 2010

ASH on

i have now my own blog .. ASH is now on !