Owlcom software
basadO wlCom  Software
Let's Owl manage your files
Welcome Screenshots Buy now Download Write to Owl Subscribe to news FAQ Links

Organization of the file system

binary-to run programs. This scheme has maximum flexibility and versatility. Using the basic system calls (or library function I / O), users can drop structured files. In particular, many DBMS store their databases in the ordinary files. The first step in structuring - storage file in a sequence of fixed-length records, each of which is the internal structure. The central idea of the scheme - operation reading on record, a record-operation and rewrite the record entirely or adds. Previously record of 80 bytes (equal to the number of positions in the punch card) or 132 characters (the width of the printer). In OS CP / M files were sequences 128-symbolic records. With the introduction of CRT terminals, this idea has lost popularity. The third way of presenting files-sequence variable-length records, each of which contains a key field in a fixed position inside the record. Basic operation, in this case, take the record with a key value. Entries can be consistently in the file (for example, as shown in value to a key fields) or in a more complex manner. Using indexes files, records depository addresses, allowing for quick access to a separate account (indeksno-posledovatelnaya organization. Adding the new record in the file, a folder where it will be determined not to put the user and the operating system. This method is used for large mainframe commercial data processing. Types and file attributes An important aspect of the file system design and OS - whether to support and recognize file types. If so, it could help correct functioning of the OS, for example, to prevent the withdrawal of the binary file to the printer. To file types supported by modern operating system, include regular (ordinary) files and directories. Normal (regular) files contain a user's information. Directories (manuals, catalogs), system files, maintaining the structure of the file system. The directory contains a list of files the motion, and fixed line between files and their characteristics (attributes). We will consider the directory below. Remember that although the file management subsystem within the normal file appears as a set of blocks external memory is provided for users of the presentation file as a linear sequence of bytes. This presentation allows the use of abstraction file when working with external devices, mezhprotsessnyh interactions with the organization, etc. So, sometimes attributed to the files other facilities operating system, for example, special symbolic files and block special file named channels and socket with a file interface. These properties are considered in other sections of the course. Next, mainly discussed on conventional files. Conventional (or regular) files actually are a set of blocks (possibly empty) for the external memory device, which is supported file system. Such files can contain both text information (usually in ASCII format) and the arbitrary binary information. Routine regular-files are ASCII and binary.
Next part
Welcome    Screenshots    Download    Buy now Write to Owl    Subscribe to Owl news   FAQ   Links  
Copyright 2004-2008 OwlCom Software .

OISV - Organization of Independent Software Vendors - Contributing Member Software Submit .NET - FREE and PREMIUM search engines submission and software submission and software promotion service. Owl Commander
Locations of visitors to this page

Valid HTML 4.01 Transitional