A physical file is a physical unit, such as magnetic tape or a disk. A logical file on the other hand is a complete set of records for a specific application or purpose. A logical file may occupy a part of physical file or may extend over more than one physical file. Sequential access method: Here the records are arranged in the ascending or descending order or chronological order of a key field which may be numeric or both.
Since the records are ordered by a key field, there is no storage location identification. It is used in applications like payroll management where the file is to be processed in entirety, i. Here, to have an access to a particular record, each record must be examined until we get the desired record.
Sequential files are normally created and stored on magnetic tape using batch processing method. Direct access files organization: Random or relative organization. Files in his type are stored in direct access storage devices such as magnetic disk, using an identifying key.
The identifying key relates to its actual storage position in the file. The computer can directly locate the key to find the desired record without having to search through any other record first. Here the records are stored randomly, hence the name random file. It uses online system where the response and updation are fast. Indexed sequential access organization: Here the records are stored sequentially on a direct access device i.
It covers the positive aspects of both sequential and direct access files. Here, the records are organized in sequence for efficient processing of large batch jobs but an index is also used to speed up access to the records. Home Contact Us. We call such storage nonvolatile. Primary storage is usually volatile, whereas secondary and tertiary storage are nonvolatile.
The objectives of computer based file organization: Ease of file creation and maintenance Efficient means of storing and retrieving information. Signal Handling E. Dynamic Memory Allocation with calloc and realloc E.
The Unconditional Branch: goto E. Unions E. Linkage Specifications E. Preprocessor F. Introduction F. The include Preprocessor Directive F. The define Preprocessor Directive: Macros F. Conditional Compilation F. The error and pragma Preprocessor Directives F. The and Operators F. Predefined Symbolic Constants F. Assertions F. Class ATM G. Class Screen G. Class Keypad G. Class CashDispenser G. Class DepositSlot G. Class Account G. Class BankDatabase G. Class Transaction G. Class BalanceInquiry G.
Class Withdrawal G. Class Deposit G. Wrap-Up Appendix H. You can do this by declaring a String variable but, as we will learn later on, most classes used to create a stream can take a string that represents the file.
If you are creating a new file, there are certainly some rules you must observe. The name of a file follows the directives of the operating system. X that is, prior to Microsoft Windows 9X , the file had to use the 8. The actual name had to have a maximum of 8 characters with restrictions on the characters that could be used. The user also had to specify three characters after a period.
The three characters, known as the file extension, were used by the operating system to classify the file. That was all necessary for those 8-bit and bit operating systems. Various rules have changed. The extension of the file is mostly left to the judgment of the programmer but the files are still using extensions.
Applications can also be configured to save different types of files; that is, files with different extensions. Based on this, if you declare a String variable to hold the name of the file, you can simply initialize the variable with the necessary name and its extension. Here is an example:. Practical Learning: Specifying the Name of a File. If you declare a string as above, the file will be created in the folder as the application. Otherwise, you can create your new file anywhere in the hard drive.
To do that, you must provide a complete path where the file will reside. A path is a string that specifies the drive such as A:, C:, or D:. The sections of a complete path string are separated by a backslash. For example, a path can the made of a folder followed by the name of the file. An example would be. A path can also consist of a drive followed by the name of the folder in which the file will be created.
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