Microsoft Excel

*What is Microsoft Excel?

Excel is an electronic spreadsheets program that can be used for storing, organizing and manipulating data.
Microsoft Excel has the basic features of all spreadsheets,using a grid of cells arranged in numbered rows and letter-named columns to organize data manipulations like arithmetic operations. It has a battery of supplied functions to answer statistical, engineering and financial needs

*What is spreadsheet modelling?

Spreadsheet modelling is a document built specially for any purposes and in any industry like in financial services, customer services etc. A model can be used to trial possibilities financially without harm in order to check how much is made, leftover, lost etc. Models are good because the formula auto update thus allowing for endless experimenting in business etc. There are many types of models such as Bank/Debt analysis, Business Planning (Budgeting) etc.

*References:

1- http://wiki.answers.com/Q/What_is_a_spreadsheet_model

2- http://spreadsheets.about.com/od/tipsandfaqs/f/excel_use.htm

3- http://en.wikipedia.org/wiki/Microsoft_Excel

System Life Cycle

Introduction

All things have a beginning, a middle and an end. And Information Technology (IT) is no different. Indeed it could be argued that IT sees more rapid change than many other technologies. Think how many 'upgrades' have happened with your favourite software.

The System Life Cycle (SLC)

The SYSTEM LIFE CYCLE is a process of stages which occur during the development of a new ICT system.

The SLC consists of the following stages:

1-Definition:

2- Investigation and analysis:

During this 'investigation and analysis' phase they will carry out very detailed investigations in order to fully understand the current system and the proposed new system.

3- Design:

This is the Design phase of the project. It is about planning the project in detail so that that system will meet user requirements.

4- Implementation:

Once the design stage has been completed the software developers can begin to write the code and actually develop the new system.

The system could either be completely bespoke with every line of code being written by specialist programmers or it could be developed from an 'off-the-shelf' application which is then customised.

5- Testing:

A team of testers will have been chosen to test the system. They are known as beta testers. Their role is to check that the system does everything exactly as specified in the system and user specification.

6- Installation:

The system has been developed and tested. It is working correctly and doing everything that was agreed during the design stage. The business is waiting in eager anticipation for the new system to be handed over to them.

7- Documentation:

The development of the user documentation is left until after the testing phase is complete. If it is created beforehand, parts of the system could change as a result of faults being discovered.User documentation is provided to the user which gives an overview of how to use the system.

8- Evaluation:

This next stage is called the 'Evaluation phase'. The evaluation stage looks at the overall project and considers how things went.

9- Maintenance:

This phase continues for the lifetime of the system. The technical documentation is essential to support the maintenance stage.

There are three kinds of maintenance needed:

1. Corrective maintenance
2. Adaptive maintenance
3. Perfective maintenance

Publishing =)

differences between central AC and normal AC

For your home, you can have a window unit or you can have Central Air. A window unit cools a relatively small area, such as one room. You may need several window units to cool your whole house.

With central air, you will have one main unit, usually situated in your attic or outside your home. It produces cool air which is then blown through large 'tubes' called ducts into vents situated throughout your home.

How do air conditioners work?

Air conditioning units contain a special chemical called a refrigerant, which has the unique ability to change from a gas to a liquid in a short amount of time. A refrigerant called freon is commonly used in air conditioning units, although there are other commercial refrigerants available. The refrigerant is pumped into the air conditioning unit at the factory, along with a small amount of lubricating oil for the compressor, an essential part of the air conditioning process.

The parts of a typical air conditioning unit usually form a closed system consisting of a compressor, a condenser, an expansion valve and a thermostat. Motorized fans help to circulate the conditioned air, while thin metal fins allow heat to dissipate quickly. The heaviest part of a typical air conditioning is often the compressor, since it must be strong enough to withstand a significant amount of pressure.