Unit – 1
DATABASE MANAGEMENT SYSTEM
Data is information such as facts and numbers used to analyze something or make decisions. Computer data
is information in a form that can be processed by a computer.
Data can come in the form of text, observations, figures, images, numbers, graphs, or symbols. For
example, data might include individual prices, weights, addresses, ages, names, temperatures, dates, or
distances. Data is a raw form of knowledge and, on its own, doesn't carry any significance or purpose.
How data is stored
Computers represent data, including video, images, sounds and text, as binary values using patterns of just
two numbers: 1 and 0. A bit is the smallest unit of data, and represents just a single value. A byte is eight
binary digits long. Storage and memory is measured in megabytes and gigabytes. The units of data
measurement continue to grow as the amount of data collected and stored grows.
Types of data
Growth of the web and smartphones over the past decade led to a surge in digital data creation. Data now
includes text, audio and video information, as well as log and web activity records. Much of that is
unstructured data.
The term big data has been used to describe data in the petabyte range or larger. Data is the raw material that
can be processed by any computing machine. Data can be represented in the form of:
Information is data that has been processed in such a way as to be meaningful to the person who receives it.
It is anything that is communicated.
Data is the term, that may be new to beginners, but it is very interesting and simple to understand. It can be
anything like name of a person or a place or a number etc. Data is the name given to basic facts and entities
such as names and numbers. The main examples of data are weights, prices, costs, numbers of items sold,
employee names, product names, addresses, tax codes, registration marks etc.
Information
Information is data that has been converted into a more useful or intelligible form. It is the set of data that has
been organized for direct utilization of mankind, as information helps human beings in their decision making
process. Examples are: Time Table, Merit List, Report card, Headed tables, printed documents, pay slips,
receipts, reports etc. The information is obtained by assembling items of data into a meaningful form. For
example, marks obtained by students and their roll numbers form data, the report card/sheet is the
.information. Other forms of information are pay-slips, schedules, reports, worksheet, bar charts, invoices and
account returns etc. It may be noted that information may further be processed and/or manipulated to form
knowledge. Information containing wisdom is known as knowledge.
,Need of Information
Modem civilization has become so complicated and sophisticated that to survive one has to be competitive.
This compels the people to keep himself informed of all types of happenings in the society. With the advent
of educational reforms in society, mankind is surrounded with a vast amount of data available. Modem
business management system has also rendered itself to bulk collection of data from various sources that needs
to be rearranged in a fashion so that it can be utilized with minimum possible time. This needs a high amount
of filing either at data stage or at information stage. No office can be without files. If you go to any tax
collection department or municipal office you will find a high amount of files stacked here and there.
Information is needed to:
• To gain knowledge about the surroundings, and whatever is happening in the society and universe.
• To keep the system up to date.
• To know about the rules and regulations and bye laws of society, local government, provincial and central
government, associations, clients etc. as ignorance is no bliss.
• Based on above three, to arrive at a particular decision for planning current and prospective actions in process
of forming, running and protecting a process or system
Difference between Information and Data:
S.NO DATA INFORMATION
Data are the variables that help to develop
ideas/conclusions.
1 Information is meaningful data.
2 Data are text and numerical values. Information is refined form of actual data.
3 Data doesn’t rely on Information. While Information relies on Data.
Information is measured in meaningful units like
time, quantity, etc.
4 Bits and Bytes are the measuring unit of data.
Data can be easily structured as the following: Information can also be structured as the
1.Tabular data 2.Graph 3.Data tree following: 1. Language 2. Ideas 3. Thoughts
5
Information carries a meaning that has been
assigned by interpreting data.
6 Data does not have any specific purpose
7 It is low-level knowledge. It is the second level of knowledge.
Data does not directly helps in decision making.
8 Information directly helps in decision making.
Data is collection of facts, which it self have no
9 meaning. Information puts those facts into context.
S.NO DATA INFORMATION
, Example of information is average score of class
10 Example of data is student test score. that is derived from given data.
RECORDS AND FILES
Data are the principal resources of an organization. Data stored in computer systems form a hierarchy
extending from a single bit to a database, the major record-keeping entity of a firm. Each higher rung of this
hierarchy is organized from the components below it.
Data are logically organized into:
1. Bits (characters)
2. Fields
3. Records
4. Files
5. Databases
Traditional file-based approach
The term 'file-based approach' refers to the situation where data is stored in one or more separate computer
files defined and managed by different application programs. Typically, for example, the details of customers
may be stored in one file, orders in another, etc. Computer programs access the stored files to perform the
various tasks required by the business. Each program, or sometimes a related set of programs, is called a
computer application. For example, all of the programs associated with processing customers' orders are
referred to as the order processing application. The file-based approach might have application programs that
deal with purchase orders, invoices, sales and marketing, suppliers, customers, employees, and so on.
Limitations
• Data duplication: Each program stores its own separate files. If the same data is to be accessed by
different programs, then each program must store its own copy of the same data.
• Data inconsistency: If the data is kept in different files, there could be problems when an item of data
needs updating, as it will need to be updated in all the relevant files; if this is not done, the data will be
inconsistent, and this could lead to errors. • Difficult to implement data security: Data is stored in
different files by different application programs.
This makes it difficult and expensive to implement organisation-wide security procedures on the data.
The following diagram shows how different applications will each have their own copy of the files they need
in order to carry out the activities for which they are responsible:
, Figure 1.1
The shared file approach
One approach to solving the problem of each application having its own set of files is to share files between
different applications. This will alleviate the problem of duplication and inconsistent data between different
applications, and is illustrated in the diagram below:
Figure 1.2
The introduction of shared files solves the problem of duplication and inconsistent data across different
versions of the same file held by different departments, but other problems may emerge, including:
• File incompatibility: When each department had its own version of a file for processing, each
department could ensure that the structure of the file suited their specific application. If departments
have to share files, the file structure that suits one department might not suit another. For example,
data might need to be sorted in a different sequence for different applications (for instance, customer
details could be stored in alphabetical order, or numerical order, or ascending or descending order of
customer number). • Difficult to control access: Some applications may require access to more data
than others; for instance, a credit control application will need access to customer credit limit
information, whereas a delivery note printing application will only need access to customer name and
address details. The file will still need to contain the additional information to support the application
that requires it.
• Physical data dependence: If the structure of the data file needs to be changed in some way (for
example, to reflect a change in currency), this alteration will need to be reflected in all application
programs that use that data file. This problem is known as physical data dependence, and will be
examined in more detail later in the chapter.
• Difficult to implement concurrency: While a data file is being processed by one application, the file
will not be available for other applications or for ad hoc queries. This is because, if more than one
application is allowed to alter data in a file at one time, serious problems can arise in ensuring that the
updates made by each application do not clash with one another. This issue of ensuring consistent,
concurrent updating of information is an extremely important one, and is dealt with in detail for
database systems in the chapter on concurrency control. File-based systems avoid these problems by
not allowing more than one application to access a file at one time.
The systems that are used to organize and maintain data files are known as file based data systems. These file
systems are used to handle a single or multiple files and are not very efficient.
Functionalities
The functionalities of a File-based Data Management System are as follows −
• A file based system helps in basic data management for any user.
DATABASE MANAGEMENT SYSTEM
Data is information such as facts and numbers used to analyze something or make decisions. Computer data
is information in a form that can be processed by a computer.
Data can come in the form of text, observations, figures, images, numbers, graphs, or symbols. For
example, data might include individual prices, weights, addresses, ages, names, temperatures, dates, or
distances. Data is a raw form of knowledge and, on its own, doesn't carry any significance or purpose.
How data is stored
Computers represent data, including video, images, sounds and text, as binary values using patterns of just
two numbers: 1 and 0. A bit is the smallest unit of data, and represents just a single value. A byte is eight
binary digits long. Storage and memory is measured in megabytes and gigabytes. The units of data
measurement continue to grow as the amount of data collected and stored grows.
Types of data
Growth of the web and smartphones over the past decade led to a surge in digital data creation. Data now
includes text, audio and video information, as well as log and web activity records. Much of that is
unstructured data.
The term big data has been used to describe data in the petabyte range or larger. Data is the raw material that
can be processed by any computing machine. Data can be represented in the form of:
Information is data that has been processed in such a way as to be meaningful to the person who receives it.
It is anything that is communicated.
Data is the term, that may be new to beginners, but it is very interesting and simple to understand. It can be
anything like name of a person or a place or a number etc. Data is the name given to basic facts and entities
such as names and numbers. The main examples of data are weights, prices, costs, numbers of items sold,
employee names, product names, addresses, tax codes, registration marks etc.
Information
Information is data that has been converted into a more useful or intelligible form. It is the set of data that has
been organized for direct utilization of mankind, as information helps human beings in their decision making
process. Examples are: Time Table, Merit List, Report card, Headed tables, printed documents, pay slips,
receipts, reports etc. The information is obtained by assembling items of data into a meaningful form. For
example, marks obtained by students and their roll numbers form data, the report card/sheet is the
.information. Other forms of information are pay-slips, schedules, reports, worksheet, bar charts, invoices and
account returns etc. It may be noted that information may further be processed and/or manipulated to form
knowledge. Information containing wisdom is known as knowledge.
,Need of Information
Modem civilization has become so complicated and sophisticated that to survive one has to be competitive.
This compels the people to keep himself informed of all types of happenings in the society. With the advent
of educational reforms in society, mankind is surrounded with a vast amount of data available. Modem
business management system has also rendered itself to bulk collection of data from various sources that needs
to be rearranged in a fashion so that it can be utilized with minimum possible time. This needs a high amount
of filing either at data stage or at information stage. No office can be without files. If you go to any tax
collection department or municipal office you will find a high amount of files stacked here and there.
Information is needed to:
• To gain knowledge about the surroundings, and whatever is happening in the society and universe.
• To keep the system up to date.
• To know about the rules and regulations and bye laws of society, local government, provincial and central
government, associations, clients etc. as ignorance is no bliss.
• Based on above three, to arrive at a particular decision for planning current and prospective actions in process
of forming, running and protecting a process or system
Difference between Information and Data:
S.NO DATA INFORMATION
Data are the variables that help to develop
ideas/conclusions.
1 Information is meaningful data.
2 Data are text and numerical values. Information is refined form of actual data.
3 Data doesn’t rely on Information. While Information relies on Data.
Information is measured in meaningful units like
time, quantity, etc.
4 Bits and Bytes are the measuring unit of data.
Data can be easily structured as the following: Information can also be structured as the
1.Tabular data 2.Graph 3.Data tree following: 1. Language 2. Ideas 3. Thoughts
5
Information carries a meaning that has been
assigned by interpreting data.
6 Data does not have any specific purpose
7 It is low-level knowledge. It is the second level of knowledge.
Data does not directly helps in decision making.
8 Information directly helps in decision making.
Data is collection of facts, which it self have no
9 meaning. Information puts those facts into context.
S.NO DATA INFORMATION
, Example of information is average score of class
10 Example of data is student test score. that is derived from given data.
RECORDS AND FILES
Data are the principal resources of an organization. Data stored in computer systems form a hierarchy
extending from a single bit to a database, the major record-keeping entity of a firm. Each higher rung of this
hierarchy is organized from the components below it.
Data are logically organized into:
1. Bits (characters)
2. Fields
3. Records
4. Files
5. Databases
Traditional file-based approach
The term 'file-based approach' refers to the situation where data is stored in one or more separate computer
files defined and managed by different application programs. Typically, for example, the details of customers
may be stored in one file, orders in another, etc. Computer programs access the stored files to perform the
various tasks required by the business. Each program, or sometimes a related set of programs, is called a
computer application. For example, all of the programs associated with processing customers' orders are
referred to as the order processing application. The file-based approach might have application programs that
deal with purchase orders, invoices, sales and marketing, suppliers, customers, employees, and so on.
Limitations
• Data duplication: Each program stores its own separate files. If the same data is to be accessed by
different programs, then each program must store its own copy of the same data.
• Data inconsistency: If the data is kept in different files, there could be problems when an item of data
needs updating, as it will need to be updated in all the relevant files; if this is not done, the data will be
inconsistent, and this could lead to errors. • Difficult to implement data security: Data is stored in
different files by different application programs.
This makes it difficult and expensive to implement organisation-wide security procedures on the data.
The following diagram shows how different applications will each have their own copy of the files they need
in order to carry out the activities for which they are responsible:
, Figure 1.1
The shared file approach
One approach to solving the problem of each application having its own set of files is to share files between
different applications. This will alleviate the problem of duplication and inconsistent data between different
applications, and is illustrated in the diagram below:
Figure 1.2
The introduction of shared files solves the problem of duplication and inconsistent data across different
versions of the same file held by different departments, but other problems may emerge, including:
• File incompatibility: When each department had its own version of a file for processing, each
department could ensure that the structure of the file suited their specific application. If departments
have to share files, the file structure that suits one department might not suit another. For example,
data might need to be sorted in a different sequence for different applications (for instance, customer
details could be stored in alphabetical order, or numerical order, or ascending or descending order of
customer number). • Difficult to control access: Some applications may require access to more data
than others; for instance, a credit control application will need access to customer credit limit
information, whereas a delivery note printing application will only need access to customer name and
address details. The file will still need to contain the additional information to support the application
that requires it.
• Physical data dependence: If the structure of the data file needs to be changed in some way (for
example, to reflect a change in currency), this alteration will need to be reflected in all application
programs that use that data file. This problem is known as physical data dependence, and will be
examined in more detail later in the chapter.
• Difficult to implement concurrency: While a data file is being processed by one application, the file
will not be available for other applications or for ad hoc queries. This is because, if more than one
application is allowed to alter data in a file at one time, serious problems can arise in ensuring that the
updates made by each application do not clash with one another. This issue of ensuring consistent,
concurrent updating of information is an extremely important one, and is dealt with in detail for
database systems in the chapter on concurrency control. File-based systems avoid these problems by
not allowing more than one application to access a file at one time.
The systems that are used to organize and maintain data files are known as file based data systems. These file
systems are used to handle a single or multiple files and are not very efficient.
Functionalities
The functionalities of a File-based Data Management System are as follows −
• A file based system helps in basic data management for any user.
