Define File Concept
File Concepts: A file is an abstract data type defined and implemented by the operating system. It is a sequence of logical records. Files are mapped by the operating system onto physical devices. A file is a named collection of related information that is recorded on secondary storage. Commonly files represent programs and data.
Data files may be numeric, alphabetic or binary. Files may be free form, such as text files or may be formatted rigidly. The information in a file is defined by its creator. Different types of information may be stored in a file – source programs object programs, executable programs, numeric data, text, payroll records, and so on.
What are the File attributes
File Attributes: A file has certain other attributes which vary from one operating system to another. Some of them are:
- Name : It is the human readable symbolic file name.
- Identifier : This unique tag, usually a number, identifies the file within the file system.
- Type : This information is needed for those systems that support different types.
- Location : This information is a pointer to a device and to the location of the file on that device.
- Size : The current size of the file and also its maximum size are included in this attribute.
- Protection : Access control information determines who can do reading, writing, executing and so on.
- Time, date and user identification : It contains date, time of file creation. It is useful for file protection,security and usage monitoring.
Define the term File System
File System: File system provides the mechanism for online storage and access to file contents, including data and programs. The file system resides permanently on secondary storage, which is designed to hold a large amount of data permanently. To provide an efficient and convenient access to the disk, the operating system imposes one or more file systems to allow the data to be stored, located, retrieved easily. The file system itself is generally composed of many different levels. The structure is shown below. Each level in the design uses the features of lower levels to create new features for use by higher levels.
Acyclic Graph Directory
Acyclic-Graph Directories: An acyclic graph allows directories to have shared subdirectories and files. The same file or sub directory may be in two different directories. An acyclic graph, that is, a graph with no cycles, is a natural generalization of the tree-structured directory scheme. An acyclic-graph directory structure is more flexible than a simple tree structure.
Tree structured directory
Tree Structured Directory: A tree is the most common directory structure. The tree has a root directory. Every file in the system has a unique path name. A path name is the path from the root, through all the sub-directories, to a specified file. With tree-structured directory, system users can access, in addition to their files, the files of other users.
Data Organization with Diagram
Data Organization: Data organization is a data management for physical and spatial arrangement of the data setting.
Data: Data is a row fact and figures.
Information : Data after processing is known as information.
Data can be represent in various ways, which is known as data model.
1. Data Entity Model : Data is used in entity relationship model for representing data.
2. Data Network Model : Data Network Model is a network model in which data records stored with links to other records. Association are known as pointer. These pointer can be node numbers or disk address.
3. Hierarchical Data Model : This model is an improvement of the flat-file database system. The relationship in the hierarchical model are child parent relationship. In hierarchical model root node have Child’s node, many child has only one root node.
Drive Organization: Drive is a storage area which store data, information and software. Computer has C, D, E, and F drives. Drives C contain all data and software which are required for completion of Installation of any type of window. Computer drive is divided many types.
1. Floppy Drive: Floppy drive is used for only floppy. We can use one floppy at a time but now a days floppy are not commonly used. So it is not much requirement.
2. CD Drive: CD drive is used for CD‘s-CD drive is divided into two form. CD drive and CD writer. CD drive is used for only read the data of CD. If we want to save data into CD then use CD writer.