Archive for September 2013
What Files Are..?
Files are the collection of data onto a permanent storage structure. They are stored on a permanent storage media such as a computer hard drive, CD ROM drive, floppy disk drive or sometimes even a tape drive. Files take a certain amount of room to store. For example if you have two text files and one file has one sentence in it while the other file has 200 sentences in it, the file with 200 sentences will use more room on the storage media.
Provide machine executable code which is used to run application programs and the operating system.
Store application program or operating system configuration information.
Store data used by the user such as Microsoft Word document files.
Therefore there are three types of information that files contain:
The main items to remember include the facts that all files take a certain amount of room on their storage media and all files have a type which indicates whether they can be run by your computer. The file extension is one indication of the file type but not the only way to determine type.
If you are browsing your files using "My Computer" and click on "View" and "Details" you will see a window showing the file characteristics like the one below. Folders only take a little room on the hard drive and do not normally take as much room as files.
File Functions
Different files have different purposes. Files are used to do one or more of the following functions:Provide machine executable code which is used to run application programs and the operating system.
Store application program or operating system configuration information.
Store data used by the user such as Microsoft Word document files.
Therefore there are three types of information that files contain:
- Executable code.
- System or program configuration information.
- User data.
File Characteristics
Files have the below characteristics:- Name
- Optional extension name - Part of the name, it is used by Windows operating systems to identify an associated program that can be used to read it
- Size - Shows the space the file requires for storage normally showed in kilobytes (Kb) which is 1000 bytes
- Type - Indicates the program used to access the file. The next section will talk more about file types.
- Date Modified - Shows the last date the file was created or changed.
- File structure - This characteristic is not view-able by the computer user but some programs can examine file structure to determine the type of file it is even when the file extension is changed.
The main items to remember include the facts that all files take a certain amount of room on their storage media and all files have a type which indicates whether they can be run by your computer. The file extension is one indication of the file type but not the only way to determine type.
If you are browsing your files using "My Computer" and click on "View" and "Details" you will see a window showing the file characteristics like the one below. Folders only take a little room on the hard drive and do not normally take as much room as files.
Linux is Multiuser, Multitasking Operating System
Many students who study Unix programming and shell scripting have a question - “How is Linux a mutlitasking operating system?”, as they work from a terminal which looks like DOS.
Let us start with basics.
There are two general types of single-user operating system:
1. Single tasking
2. Multitasking systems.
Single tasking systems are the systems which are designed to manage the computer so that one user can effectively do one thing at a time.
The Palm OS for Palm hand held computers is a good example of a modern single-user, single-task operating system. DOS is also one the examples.
Multitasking refers to an operating system in which multiple processes, also called tasks, can execute (i.e., run) on a single computer seemingly simultaneously and without interfering with each other. That is, each process has the illusion that it is the only process on the computer and that it has exclusive access to all the services of the operating system.
Windows 95, Windows 98, Windows NT workstations and older Mac system are the examples of single user multitasking operating system.
Linux, Unix, VMS and mainframe operating systems, such as MVS, are examples of multi-user operating systems.
There can be more than one users on a Linux system who can login through terminals simultaneously. This way Linux is multiuser OS.
Next time when you login in your Linux/Unix classes, try to run who command. You may find more than one users logged from different terminals along with you. The processes of different users are separate from each other and they get the CPU share equally. The CPU preempts very fast and so Linux is a mutlitasking OS. In fact when you run ps command you will get the name of processes being run from your terminal. And in order to get all the processes being run by the OS type ps aux command.
Linux terminal can run your processes in background too. Append a '&' to your command and run ps. You will get the job being run in background and at the same time your terminal free for next job.
Let us start with basics.
A single-user operating system is a type of operating system that is developed and intended for use on a computer or similar machine that will only have a single user at any given time. This is the most common type of OS used on a home computer, as well as on computers in offices and other work environments.
There are two general types of single-user operating system:
1. Single tasking
2. Multitasking systems.
Single tasking systems are the systems which are designed to manage the computer so that one user can effectively do one thing at a time.
The Palm OS for Palm hand held computers is a good example of a modern single-user, single-task operating system. DOS is also one the examples.
Multitasking refers to an operating system in which multiple processes, also called tasks, can execute (i.e., run) on a single computer seemingly simultaneously and without interfering with each other. That is, each process has the illusion that it is the only process on the computer and that it has exclusive access to all the services of the operating system.
Windows 95, Windows 98, Windows NT workstations and older Mac system are the examples of single user multitasking operating system.
A multi-user operating system allows many different users to take advantage of the computer's resources simultaneously. The operating system must make sure that the requirements of the various users are balanced, and that each of the programs they are using has sufficient and separate resources so that a problem with one user doesn't affect the entire community of users.
Linux, Unix, VMS and mainframe operating systems, such as MVS, are examples of multi-user operating systems.
There can be more than one users on a Linux system who can login through terminals simultaneously. This way Linux is multiuser OS.
Next time when you login in your Linux/Unix classes, try to run who command. You may find more than one users logged from different terminals along with you. The processes of different users are separate from each other and they get the CPU share equally. The CPU preempts very fast and so Linux is a mutlitasking OS. In fact when you run ps command you will get the name of processes being run from your terminal. And in order to get all the processes being run by the OS type ps aux command.
Linux terminal can run your processes in background too. Append a '&' to your command and run ps. You will get the job being run in background and at the same time your terminal free for next job.
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