Main-Memory Management

Main-Memory Management
Main Memory is a large array of words, ranging in size from hundreds of thousands to billions. Each
word or byte shared by the CPU and I/O devices. The central processor reads instructions from main
memory during the instruction-fetch cycle, generally the only large storage device that the CPU is able
to address and access directly. For example, for the CPU to process data from disk, those data must
first the transferred to main memory by CPU-generated I/O calls. Selection of a memory-management
scheme for a specific system depends on many factors-especially on the hardware design of the system.
File Management
Computers can store information on several different types of physical media. Magnetic tape, magnetic
disk, and optical disk physical organization. A file is a collection of related information defined by its
creator. Commonly, files represent programs and data. File Consists of a sequence of bits, bytes, lines,
or records whose meanings are defined by their creators of bits, lines or records whose meanings are
defined by their creators. The Operating System file by managing mass storage media, such the devices
that control them. Files are normally organized into directories to ease their use. When multiple users
have access to files, we any want to control by whom and in what ways.
Secondary-Storage Management
The main purpose of a computer system is to execute programs. These programs in main memory,
or primary storage, main memory is too small to accommodate all data and programs, the data that it
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holds are lost when power is lost, the computer system must provide secondary storage to back up main
memory. Computer systems use disks as the principle on-line storage medium, for both programs and
data. the proper management of disk storage is of central importance to a computer system.