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4 Files

A file is a unit that a computer uses to manage information. The data management function of an OS can be described as a function to manage files. This section introduces file organization formats and access methods.

4 - 1 Files and Records

Below is a list of the units of information in a computer.

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4-1-1 Classification of Records

(1) Physical records and logical records

In a computer, data is processed in units of records, which have meaning. However, to handle records that are actually stored on an auxiliary storage device, it is not efficient to perform input and output on a record basis, so this is performed with a unit that groups multiple records called a block. This block, which is an input/output unit, is referred to as a physical record as it is a record that is handled physically. This is distinguished from a record that forms a processing unit, which is called a logical record.

(2) Record formats

Below is the classification of record formats.

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4-1-2 Classification of Files

File classifications include classifications depending on the purpose of usage, storage (or usage) period, users, or such other factor. These classifications are separate from the file access methods and organization format that are described later.

(1) Classification based on purpose of usage

(2) Classification by storage (or usage) period

(3) Classification based on users

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