Connect With Computers

  File System Linux treated everything as a file. Ever a directory is treated as a file and contains entries for several other files. All the hardware devices, such as (input/output) I/O devices, storage devices, etc. are all treated as files. The Linux file system is organised in a hierarchy which start with the root directory. The root directory is represented by forward slash (/) under the root directory there are several system directories and the name directory. /bin : - This directory contains executable program file (binary file). This directory contains all the commands of Linux in the same way as all the commands of DOS are stored in the Command.Com file. /dev : - This directory contains the special device files for example, the printer may be a file known as prn in this directory. The hard disk may be hda file and its first partition would be hda.   /etc : - This directory contains all the system wise configuration information as text files. /lib : - This directory cont

  Linux operating system Linux is a multi-user, multi-tasking operating system first developed by Linus Benedict Torvalds in the year 1991 . Linux is a 32-bit operating system. It runs on a wide variety of platforms, such as Intel, Sparc, Alpha , etc. it can be considered in every sense as a full-blown implementation of UNIX. But it cannot be called as UNIX because UNIX is a registered trademark product owned by AT&T (American Telephone and Telegraph). Linux is distributed as afree software under a free software licence called the GNU General Public Licence (GPL). Basic Linux Elements The basic elements of Linux are discussed in the following sub-sections:   Kernel The Kernel is at the core of LINUX system and is loaded into the memory as soon as the system starts up. It manages main memory, files and peripheral devices. Maintaining the time, date, launching applications, and allocating system resources are also the function of this part of the operating system. Shell

DOS Commands 1) Internal Commands   Internal Commands are also called memory resident commands because these commands are automatically loaded on the memory at the time of booting. All the internal commands are stored in the file Command.com.   Following are some important Internal Commands.   1) VER It displays the version of operating system. that you are using.          C:\>VER   2) VOL It displays the volume label of the hard disk.         C:\>VOL Volume label in drive C: is JJ infotech.                  C:\>VOLD Volume drive D has no label.   3) DATE This command is used to display the current system date and also allow you to change it. C:\>DATE   4) Time This command is used to display the current system time and also allow you to change it. C:\>Time   5) Exit It is used to exit from DOS . C:\Exit   6) CLS This command is used to clear the DOS screen. C:\>CLS   7)DIR This command is used to

Command Prompt (DOS) MS-DOS is a single user, single tasking and character user interface (CUI) operating system. It creates a text environment for the computer. To do any work on DOS we have to give commands to the computer. It is and operating system with a command line interface used on personal computers. You type MS-DOS commands using a command prompt window. MS-DOS commands are typed at an entry point identified by a blinking cursor. To get command through Windows operating system, we do the following Open a Command Prompt,   Click on the Start button.   Click on All programs.   Choose Accessories. And then click on Command Prompt. Shortcut key to open DOS :- Click start and type command or CMD and press ENTER or Press window button +R and type Command Prompt and press ENTER . System Prompt :-System prompt represents the current drive and folder. Cursor :- Cursor is a blinking bar just after the system prompt which represent the position on the screen where the cha

Difference between Compiler and Interpreter Do you ever hear about Compiler and Interpreter? These are the programs which translates the high level language into machine language. Let’s know more about these programs. Compiler A program that translates high level language program into machine language program is known as compiler. It checks all kinds of limits, ranges, errors etc. But its program execution time is more and occupies a larger part of the memory. It has low speed and low efficiency of memory utilization. If a compiler runs on a computer for which it produces the object code it is known as a self or resident compiler , If a compiler runs on a computer other than that for which it produces object code, it is known as a cross compiler . The compiler derives its name from the way it works, looking at the entire piece of source code and collecting and reorganizing the instructions. Compilers require some time before an executable program emerges. However, programs prod

CACHE Memory Cache memory is placed in between the CPU and the main memory. It is faster than the main memory. Hence access time is much less than that of the main memory. The access time of a cache memory is 15-25 nanoseconds (ns) whereas that of the main memory is 80 ns . One nanosecond =10 9   second. The cache memory stores the data and instructions which are to be immediately executed. It is used to reduce average access time for address, instructions or data which are normally stored on the main memory. Thus it increases the operating speed of the system. Cache memory is much costlier than the main memory. From economical considerations, the size of cache memory is usually smaller than that of the main memory. Sometime cache is used to store only instructions. One such type of cache is used in 68020 processor. It has 256 bytes instruction cache, which allows it to pre-fetch instructions from the main memory and store them in the cache during the period when the system bus woul

Virus  Virus stands for Vital Information Resources Under Seige. Virus is a harmful program written for destructive purpose. Different kinds of virus perform different kinds of activity. Some virus delete programs some virus replicate themselves and make their own copies. Viruses are program in such a way that they could enter in the computer without the knowledge of the user. How does a computer virus attack? Once a virus has successfully attached to a program, file, or document, the virus will lie dormant until circumstances cause the computer or device to execute its code. In order for a virus to infect your computer, you have to run the infected program, which in turn causes the virus code to be executed. This means that a virus can remain dormant on your computer, without showing major signs or symptoms. However, once the virus infects your computer, the virus can infect other computers on the same network. Stealing passwords or data, logging keystrokes, corrupting files, spamming