Understanding Data Organization: Files, Records, and Structures
Understanding Data Organization
LOGICAL RECORD – A homogeneous unit of information composed of data relating to a particular object or concept.
FIELD – An elementary unit of information within a logical record.
PHYSICAL RECORD – A unit of transmission or storage of information in auxiliary memory. It is a set of information that, depending on the characteristics of the machine, can be stored or read at one time. Often called a BLOCK. In general, a block consists of a variable number of logical records, meaning multiple logical records can be transferred in a single read/write operation. Normally, a block supported on a floppy disk or a hard disk has a storage capacity of 512 bytes.
FILE – A set of related records treated for the purposes of a process, as a collection of simple units of information with the same characteristics in terms of structure, meaning, and treatment. That is, a file is a set of data having a logical relationship to each other and are stored in a user-appropriate manner to communicate with the computer. A file stores information concerning the same subject, in a structured way to manipulate the data individually.
From the above definitions, a file consists of records, grouped or not in blocks, which form a collection stored in storage hardware.
Types of Files
Files can be classified according to different criteria:
a) By subject matter:
- Text
- Binary
b) By utility:
- Permanent
- Master or Location
- Movements
- Historical
- Temporary
c) By the organization of data and file access method:
- Sequential Files
- Direct Access Files (or Random)
- Indexed Files
Logical Organization of Data
A data structure is a collection of data that can be characterized by its organization and the operations that might be defined on that structure.
Data can be simple (i.e., not formed by other data structures), which are associated with a variable in almost all programming languages (Integer, Character, Real, etc.), or structured, which are aggregations of simple data, with the character string being the most representative. A common feature of structured data is that an identifier or name can represent multiple individual data, allowing each of these to be referenced independently.
An important feature that differentiates the types of data is that data in each variable represents a single element, whereas structured data share the common feature of having an identifier (name of the structure) that can represent multiple individual data that can be referred to individually.
Regarding the organization of data in computer memory, they can be structured as:
- STATIC STRUCTURES – Those in which the size is assigned in computer memory, defined and determined before running the program, and cannot be changed during program execution. Such structures are implemented in almost all programming languages and represent records, files, and arrays.
- DYNAMIC STRUCTURE – Those that offer no limitations or restrictions on the occupation of computer memory during program execution. They require the use of a specific data type (pointer), which is not supported by many programming languages. The main dynamic structures are lists, trees, and graphs.
Records, Logical and Physical Records, Files
The information contained in secondary memory devices is divided into files. A FILE is a collection of bytes stored in an organized manner in a secondary memory device. From the point of view of the file, its information is stored in units called records.
A record is the structure capable of storing data as homogeneous units of information within an information store (file). It is composed of smaller structures called fields.
The concept of a record can be used in both hardware (physical record) and software (logical record) with the following meanings and definitions:
RECORD – A structure for storing digital information and redistributing it under certain conditions. It represents the unit of structured information, straightforward and uniform, that can be manipulated as a whole. It is the simplest data structure that makes up files; that is, a file consists of a set of homogeneous records.