Text 13 using software

Software is the set of programs, procedures, and related documentation associated with a computer system. A program is a coded set of instructions that interprets the information you give to the computer with the keyboard or a mouse, and directs your computer to carry out a task.

Different kinds of software perform different kinds of tasks. Examples kinds of software are operating systems, such as MS-DOS, Windows 95 and its enhanced versions and programs Microsoft Excel and Microsoft Office. There is a wide variety of software programs including word processors, accounting packages, computer-aided design systems and games.

The operating system gets your computer running and controls the operation of your computer's activities. It manages the flow, entry, and display of software and data to and from each part of your computer system. To run a program, you first need to run the operating system. Some years ago the Microsoft disk operating system (MS-DOS) or a computer manufacturer's version of MS-DOS was the operating system most widely used with personal computers. Nowadays it is Windows 98, 2000, XP and others.

When you start a program, you see information on your screen, such as menus and commands. While you are using a program, the operating system is managing your computer's activities. It moves instructions and files from one part of your computer system to another as you choose commands and type information.

Text 14 using files and directories

The information your computer uses is stored on disks in files. A file is a collection of related information such as a computer program or the text of a letter. Each file is given a unique name, and each filename is stored in a directory. To find out about the files in a directory, use the MS-DOS command DIR. The instructions used to run a program are stored in program files, and the information you create by using a program is stored in data files.

As you work with a program, operating system processes the information stored in program files and passes it along to your system when it is needed. When you are finished using the program, your data files are stored on a disk.

When referring to a file, you must use a file specification. This consists of a pathname, a filename and an extension (if there is one).

File extension can be up to three characters long and are used to identify the contents of a file. MS-DOS automatically defines the meaning of some file extensions. Others can be assigned as you wish. For example, .TXT can be used to indicate a text file.

You assign each file a name so that you can identify its contents.

Organizing your files into directories and subdirectories on a disk is like organizing your documents into file folders and then storing them in the drawers of a file cabinet.

Operating system has rules for naming files. It also includes several commands that you can use to work with files.

Text 15 Organizing Files into Directories

A disk can hold several hundred or even thousands of files, depending on its size. The more files you have, the more difficult it is to keep track of them. To help you keep track of your files, you can use operating system commands to group your files into directories. MS-DOS lets you organize the files on your disk into directories. Directories are a way of dividing your files into convenient groups. Just as file folders in a file cabinet contain groups of related documents, directories contain groups of related files, such as the minutes and expense reports you create by using a word-processing program. You assign each directory a unique name so that you can identify it.

Using Subdirectories. A directory may contain any number of files, but it is often more convenient to separate the files into subdirectories. When your directories become too large, you can use OS to create additional directories to further organize your files. A directory within another directory is called a subdirectory. This method of organizing the disk is rather like a tree where the files are the leaves of the tree and the directories are the branches. (The first directory is usually called the "ROOT").

You can have more than one file (leaf) with the same name if the files are in different directories.

The organization of directories, subdirectories, and files is called the directory tree. When you format a disk, OS creates one large directory, called the root directory, on the disk. All other directories you create branch out from the root directory.

Each directory has at least two entries, even when otherwise empty. These are ' . ' and ' .. '. The ' . ' specifies the name of the current directory and the '.. ' the name of the parent directory.

OS needs a pathname to find its way to a particular file. The pathname is a series of directory names followed by the required filename, each separated from the last by a backward slash (\). If a file specification does not begin with \ the first part of the specification is taken to be default, or current, directory.

You must tell the computer which directory it must use as its current working directory – that is, the directory you wish to work in.

For example, within your STATUS directory, you could organize your status reports by month if you create a subdirectory for each month. The subdirectory STATUS\JAN would hold the status reports you wrote in January, STATUS\FEB would hold the ones you wrote in February, and so on.

Multilevel Directories. When there is more than one user on your computer, or when you are working on several different projects, the number of files in the directory can become large and unwieldy. To deal with this large number of files, you may want to keep your files separate from a coworker's or organize your programs into convenient categories.

In an office, you can separate and organize files that belong to different people or that relate to specific projects by putting them in different file cabinets. For example, you might put your accounting programs in one file cabinet and your letters in another. You can do the same thing with MS-DOS by putting your files into different directories.

Directories let you group your files in convenient categories. These directories, in turn, may contain other directories (referred to as subdirectories). This organized file structure is called a multilevel directory system.

Note: The maximum number of files or directories that the root directory may contain varies, depending on the type of disk and disk you are using. This maximum capacity for a root directory may vary depending upon how the disk is formatted. The number of subdirectories on a disk is not restricted.

The first level in a multilevel directory is the root directory, which is created automatically when you format a disk and start putting files on it. Within root directory, you can create additional directories and subdirectories.

As you create new directories for groups of files, or for other people using the computer, the directory system grows. Moreover, within each new directory you can add new files or create new subdirectories.

You can move around in the multilevel system by stating at the root and "traveling" through intermediate subdirectories to find a specific file. Conversely, you can start anywhere within the file system and travel toward the root. On the other hand, you can go directly to any directory without traveling through intermediate levels.

The directory that you are in is called the working directory. The filenames and commands discussed in this chapter relate to your working directory and do not apply to any other directories in the structure. When you start your computer, you start out in the working directory. Similarly, when you create a file, you create it in the working directory.

Because you can put files in different directories, you and your coworkers can have files with the same names, but with unrelated content.