What are the DBMS functions?

DBMS provides the following functions:

Concurrency: 
      Concurrent access (meaning 'at the same time') to the same database by multiple users

Security: 
      Security rules to determine access rights of users

Backup and recovery: 
      Processes to back-up the data regularly and recover data if a problem occurs

Integrity: 
      Database structure and rules improve the integrity of the data

Data descriptions: 
      A data dictionary provides a description of the data

What is database manager system (DBMS) and which are their elements?

A database management system (DBMS) is system software for creating and managing databases.
The DBMS provides users and programmers with a systematic way to create, retrieve, update and manage data.

A DBMS consists of the following three elements:

The physical database:
        The collection of files that contain the data

The database engine:
        The software that makes it possible to access and modify the contents of the database

The database scheme:
        Specification of the logical structure of the data stored in the database

Prepare a timeline with the 5 database generations. Each generation must have a brief description and a representative Image.

Describe briefly the five database generations

First generation (50's and 60's): 

Files on tapes or cards.
The file systems used batch sequential processing only.

Second generation (60's): 

Files on disks.
The file systems allowed multiple direct access to random locations of a disk.

Third generation (mid 60's and 70's): Early database systems:

Systems started to separate logical and physical data structures.
Systems started to use implementation oriented data models, mainly including the hierarchical
model and the network model.

Fourth generation (80's): Relational systems:

Systems provided powerful, set-oriented query languages

Fifth generation (90's and 00's): Post-relational systems:

Designers are developing new systems that have enhanced functionality, more complex data,
and can serve a broader class of applications.

What is a database model, identify the different types of database according to the model. Find a representative image of each kind of model.

A database model is a type of data model that determines the logical structure of a database and fundamentally determines in which manner data can be stored, organized, and manipulated.

DATABASE MODELS:

Flat model
Early data models :Hierarchical model, Network model and Inverted file model
Relational model 
Post-relational model: Graph model, Multivalue model and Object-oriented database models

Define the next database concepts: Database, Table, Record, Field, Data type, Sort

Database :  A tool to help organize, sort, and search a collection of related information
Table : A collection of data that is stored in rows and columns
Record : A row on a datasheet and is a set of values defined by fields
Field : A column on a datasheet and defines a data type for a set of values in a table
Data type : The type of value that will be entered into the fields
Sort : The process of putting your data into a logical order

Which are the main advantages /disadvantages of the different types of files organization?

ADVANTAGES:

Sequential:
Simple file design. Very efficient when most of the records must be processed or if the data has a natural order . Can be stored on inexpensive devices like magnetic tape.

Indexed Sequential: 
Flexibility and faster than sequential

Direct Access/Random Access: 
Speed of record processing, any record can be directly accessed and concurrent processing is possible.

DISADVANTAGES:

Sequential: 
Overall processing is slow. The entire file must be processed even if a single record is to be searched.

Indexed Sequential: 
Extra storage space for index is required.

Direct Access/Random Access:
More complex than sequential and more backup problems.

Identify the kind of files according to the organization and give a very brief description.

Type of files organization:

Serial :
A collection of records without sequence.The records are stored in the order received.
Sequential:
A collection of records with sequence.Adding/deleting records requires new files.
Indexed Sequential:
The records are stored at known address.The address is calculated by applying a mathematical function to the key field.
Direct Access/Random Access: 
They are stored on a direct access backing storage medium.

What are the files categories according to the format? Give a brief description

We can classify files in:

ASCII:
       They are file that consists of ASCII characters. You can view them in a text editor like notepad . When you store the character "a", in fact, you are storing the ascii value, the number 61.

BINARY: 
       They are files that store a secuence of bits ( 0's and 1's). They are intended to be interpreted as something other than text characters.

Why do you think databases are so important on business?

A database manages data efficiently and allows users to perform multiple tasks with ease. It allow the company to avoid data duplication and inconsistency . With a Database the data can be added and removed easily data and there is no security problems.