file management Flashcards
File management
is the storing, naming, sorting and handling computer files
file
named collection of related information that is recorded on secondary storage such as magnetic disks, magnetic tapes and optical disks
File Concept
A file is a collection of similar records
Path
The path refers to the exact location of the file and indicates to the computer user the entire sequence that must be followed to find the file
File Extension
The file extension appears after the period in the filename and is used to indicate the type of format the file is in.
Zipping (Compressing
Zipping is the process of packaging a folder that contains multiple files into a single file (called a “Compressed” or “Zipped” folder).
File Attributes
- Name – only information kept in human-readable form.
- Identifier – unique tag (number) identifies file within file system
- Type – needed for systems that support different types
- Location – pointer to file location on device
- Size – current file size
- Protection – controls who can do reading, writing, executing
- Time, date, and user identification – data for protection, security, and usage monitoring
- Information about files are kept in the directory structure, which is maintained on the disk
File Operations
Create: A new file is defined and positioned within the structure of files.
Delete: A file is removed from the file structure and destroyed.
Open: An existing file is declared to be “opened” by a process, allowing the process to perform functions on the file.
Close: The file is closed with respect to a process, so that the process no longer may perform functions on the file, until the process opens the file again.
Read: A process reads all or a portion of the data in a file
Write: A process updates a file, either by adding new data that expands the size of the file or by changing the values of existing data items in the file
Operations on Files
Creating a file
Reading a file
Writing a file
Deleting a file
Repositioning in a file
Truncating a file
File Types – Name, Extension
File type refers to the ability of the operating system to distinguish different types of file such as text files source files and binary files
Ordinary files
- These are the files that contain user information
Directory files
- These files contain list of file names and other information related to these files
Special files
- These files are also known as device files.
- These files represent physical device like disks, terminals, printers, networks, tape drive etc.
Types of special files
- Character special files - data is handled character by character as in case of terminals or printers.
- Block special files - data is handled in blocks as in the case of disks and tapes
File Management Systems
A file management system is that set of system software that provides services to users and applications in the use of files
objectives for a file management system
- To meet the data management needs and requirements of the user which include storage of data and the ability to perform the aforementioned operations.
- To guarantee, to the extent possible, that the data in the file are valid.
- To optimize performance, both from the system point of view in terms of overall throughput.
- To provide I/O support for a variety of storage device types.
- To minimize or eliminate the potential for lost or destroyed data
File-System Mounting
The stem is given the name of the device, and the location within the file structure at which to attach the file system
File Access Mechanisms
File access mechanism refers to the manner in which the records of a file may be accessed. There are several ways to access files:
* Sequential access
* Direct/Random access
* Indexed sequential access
Sequential access
A sequential access is that in which the records are accessed in some sequence, i.e., the information in the file is processed in order, one record after the other
Direct/Random access
- Random access file organization provides, accessing the records directly.
- Each record has its own address on the file with by the help of which it can be directly accessed for reading or writing.
- The records need not be in any sequence within the file and they need not be in adjacent locations on the storage medium
Space Allocation
- Contiguous Allocation
- Linked Allocation
- Indexed Allocation
Contiguous Allocation
- Each file occupies a contiguous address space on disk.
- Assigned disk address is in linear order.
- Easy to implement.
- External fragmentation is a major issue with this type of allocation technique
Linked Allocation
- Each file carries a list of links to disk blocks.
- Directory contains link / pointer to first block of a file.
- No external fragmentation
- Effectively used in sequential access file.
- Inefficient in case of direct access file.
Indexed Allocation
- Provides solutions to problems of contiguous and linked allocation.
- An index block is created having all pointers to files.
- Each file has its own index block which stores the addresses of disk space occupied by the file.
- Directory contains the addresses of index blocks of files
What is file security?
File security is all about safeguarding your business-critical information from prying eyes by implementing stringent access control measures and flawless permission hygiene
Type of File protection
- File Permissions
- Encryption
- Access Control Lists
- Auditing and Logging
