Chapter 1: Data Basics

Data: Collection of raw facts, figures, and statistics related to an object (person, event, etc.). Data is unprocessed and serves as input for processing.

Information: The processed and organized form of data. It is meaningful, useful for decision-making, and serves as output.

The process of manipulating data to achieve required objectives/results. Activities include:

• Data Capturing: Recording data (e.g., source documents).
• Data Manipulation: Classifying, Calculation, Sorting, Summarizing.
• Managing Output: Storage, Retrieval, Communication, Reproduction.

Field: Smallest unit of data (e.g., Student Name).
Record: Collection of related fields (e.g., Student's complete biodata).
File: Collection of related records (e.g., Student File).

File Types (Usage):

• Master File: Stores constant information for long periods. Updated periodically.
• Transaction File: Stores input data before processing. Temporary file.
• Backup File: Additional copy of data for recovery. Permanent file.

File Organization:

• Sequential: Records stored one after another. Slow access.
• Direct/Random: Records stored using key value calculation. Fast access.
• Indexed Sequential: Records stored in order with an index. Supports both sequential and random access.

Definition: Each department has its own set of files and application programs. Records in one file are not related to records in other files.

Problems:

• Data Redundancy: Duplication of data in multiple files. Wastes storage.
• Data Inconsistency: Same data exists in different files with different values (e.g., address change updated in one file but not another).
• Program-Data Dependency: Change in file format requires change in application program.
• Lack of Flexibility: Hard to retrieve ad-hoc reports.
• Integrity Problems: Difficult to enforce constraints (e.g., Marks 0-100).
• Security Problems: Difficult to provide different levels of access.

Definition: Collection of logically related data (Database) + Programs to manage it (DBMS). Computerized record-keeping system.

Components:

• Data: The facts stored in database. Most important component.
• Hardware: Physical components (Storage, I/O devices, Memory).
• Software: DBMS, OS, Application Programs.
• Personnel: DBA, Application Programmers, End Users.

Database Models:

• Hierarchical: Tree-like structure. Parent-Child relationship (1:N).
• Network: Graph-like structure. Child can have multiple parents. Complex.
• Relational: Table-based (Relations). Most flexible and common.

Definition: Collection of programs to create, maintain, and access databases efficiently.

Objectives:

• Shareability: Data shared by multiple users/applications.
• Availability: Data available when required.
• Evolvability: Ability to change database structure.
• Integrity: Accuracy and consistency of data.

Features:

• Data Dictionary: Stores data definitions (meta-data).
• Utilities: Backup, Recovery, etc.
• Query Language (SQL): CREATE, SELECT, INSERT, etc.
• Report Generator: Produce formatted reports.
• Access Security: Passwords and privileges.

Advantages: Data Independence, Redundancy Control, Consistency, Complex Data Relationships, Security, Backup/Recovery.