Computer Sciene of Udayana State University

February 19, 2009

Definition of System (1st Quiz)

Filed under: Computer Science — ignaga @ 1:30 PM

There are many definitions about system such as:

  1. aggregation of things so combined to form an integral or complex whole [Encyclopedia Americana]
  2. interdependent group of items forming a unified whole [Webster]
  3. combination of components that act together to perform a function not possible with any of the individual parts [IEEE:Electronic Terms]

But generally the definition of system can be divide into 2 approaches :

1.  Procedure Approach

System is a working network of procedures that interact together to perform an act or to
serve a certain purpose

2.  Element/Component Approach

A System is a set of components that interact with one another and serve for a common purpose
or goal

Characteristics of System

Filed under: Computer Science — ignaga @ 1:25 PM

system has nine main characteristics:

1. Components.
2. Interrelationships.
3. Boundary.
4. Purpose.
5. Environment.
6. Input.
7. Output.
8. Interface.
9.Constraints.

A component is either an irreducible part or an aggregate of parts, also called a subsystem. The
simple concept of a component is very powerful. For example, in case of an automobile we can
repair or upgrade the system by changing individual components without having to make
changes the entire system.

• The components are interrelated; that is, the function of one is somehow tied to the function of
the others. For example, in the Store system the work of one component, such as producing a
daily report of customer orders, may not progress successfully until the work of another
component is finished, such as sorting customer orders by date of receipt.

• A system has a boundary, within which all of its components are contained and which
establishes the limits of a system, separating it from other systems.

• All of the components work together to achieve some overall purpose: the system’s reason for
existing.

• A system operates within an environment – everything outside the system’s boundary. The
environment surrounds the system, both affecting it and being affected by it. For example, the
environment of a university includes prospective students, foundations, funding agencies and the
new media. Usually the system interacts with its environment. A university interacts with
prospective students by having open houses and recruiting from local high schools.

• The point at which the system meets its environment are called interface.

• A system must face constraints in its functioning because there are limits to what it
can do and how it can achieve its purpose within its environment. Some of these constraints are
imposed inside the system (e.g., a limited number of staff available).
Others are imposed by the environment (e.g., due to regulations).

• A system interact with the environment by means of input and output. Input is anything
entering the system from the environment; output is anything leaving the system crossing the
boundary to the environment . Information, energy, and material can be both input and output in
relation to the environment. People, for example, take in food, oxygen, and water from the
environment as input. An electrical utility takes on input from the environment in the form of
raw materials (coal, oil, water power, etc), requests for electricity from customers. It provides for
output to the environment in the form of electricity.

Classification of System

Filed under: Computer Science — ignaga @ 12:08 PM

1. Abstract System and Physical System

  • An abstract system is conceptual, a product of a human mind. That is, it cannot be seen or pointed to as an existing entity. Social, theological, cultural systems are abstract systems. None of them can be photographed, drawn or otherwise physically pictured. However, they do exist and can be discussed, studied and analyzed.
  • A physical system, in contrast, has a material nature. It is based on material basis
    rather than on ideas or theoretical notions. Computer system is one of example for physical system.

2. Natural System and Unnatural System

  • Natural system is system that made naturally without human intervention. For example, a lake, a mountain, and so on.
  • Unnatural system is system that made with human intervention. For example, a plane, a factory, a car, a ship and so on.

3. Deterministic System and Probabilistic System

  • Deterministic system is limit scope system that has a fix purpose. This system operates with certain ways. Interaction between the parts are known. For example, computer programs.
  • Probabilistic System is probability things, always have a little error when the system is running. For example, stock product.

4. Simple System and Complex System

  • Simple system is system that include small number of elements, few interactions, attributes are predetermined, interaction are highly organized, well defined laws govern behavior, system does not evolved over time, sub-systems does not pursue their own goals, unaffected by behavioral influence, and largely closed to environment.
  • A complex system is a system composed of interconnected parts that as a whole exhibit one or more properties (behavior among the possible properties) not obvious from the properties of the individual parts. A system’s complexity may be of one of two forms: disorganized complexity and organized complexity.[1] In essence, disorganized complexity is a matter of a very large number of parts, and organized complexity is a matter of the subject system (quite possibly with only a limited number of parts) exhibiting emergent properties. Examples of complex systems include ant colonies, human economies, climate, nervous systems, cells and living things, including human beings, as well as modern energy or telecommunication infrastructures. Indeed, many systems of interest to humans are complex systems. Complex systems are studied by many areas of natural science, mathematics, and social science. Fields that specialize in the interdisciplinary study of complex systems include systems theory, complexity theory, systems ecology, and cybernetics[http://en.wikipedia.org/wiki/Complex_system_definition]

5. Closed System and Open System

  • Closed sytem self contained system. This system is not depend on outer environment. For example, chemestry reaction on the tube.
  • Open system is a system that depend on outer environment. Adaptability system for the environment changing. This system can keep its exist.  For example, business organization.

Methods of System’s Study

Filed under: Computer Science — ignaga @ 11:48 AM

There are several important system’s concepts that help to study a system and understand
its functioning:
• Decomposition
• Modularity
• Coupling
• Cohesion

• Decomposition is the process of breaking down a system into its smaller components.
These components may themselves be systems (subsystems) and can be broken down into
their components as well. How does decomposition aid understanding of a system? It results in smaller and less complex pieces that are easier to understand than larger, complicated pieces

• Modularity is a direct result of decomposition. It refers to dividing a system into chunks
or modules of a relatively uniform size. Modules can represent a system simply, making it
easier to redesign and rebuild. For instance, a portable CD player, as a system, accepts CDs
and settings of volume and tone as inputs and produces music as output. It includes the
separate systems as its subsystems: 1) read the digital signals from CDs; 2) amplify the
signals; 3) turn the signals into sound waves; and 4) control the volume and tone of the
sound

figure 1.2

figure 1.2

• Coupling means that subsystems are dependent on each other. But they should be as
independent as possible. If one subsystem fails and other subsystems are highly dependent
on it, the others will either fail themselves or have problems functioning.

• Cohesion is the extend to which a subsystem performs a single function. In the CD player
example, signal reading is a single function.

Definition of Information

Filed under: Computer Science — ignaga @ 11:39 AM
  • Information is processing data into more useful things for the user who need it
  • Source of the information is data
  • Data is the fact that describe events and real integrity
  • Events are things that happen on certain time
  • Fact and entity is a real object

Classification of Information

Filed under: Computer Science — ignaga @ 11:36 AM

1.  Strategic information
Use to make long period decision.
2.  Tactic information
Use to make short period decision.

Quality and Value of Information

Filed under: Computer Science — ignaga @ 11:31 AM

Quality of information depends on 3 things such as:

  • accurate : information must be free from mistakes and not confusing
  • timeliness : information that comes to user can not be late
  • relevance : information must have advantages for the user

For example:
If we read a newspaper every morning, we can measure the quality of information in newspaper
from 3 things above:
· Accurate –> the information in the newspaper must real things according to the fact
· Timeliness –> new information must be sent early
· relevance –> what the user find in the information that he read in the newspaper can used for his job

value of information is depend on 2 factor, advantages and cost.

“An information has a high value if the advantages more effective than the cost to get it “

Information Cycle

Filed under: Computer Science — ignaga @ 11:21 AM
figure 1.3

figure 1.3

In the information cycle, database has an important role because data that we input are processed
in the database system. The output after data has been processed is an information. So, user
(acceptor the information) can use that to make a decision action. Result of the decision action is
new data. New data comes for the input so information is being cycling again continuously.

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