- Created by: Jonathan
- Created on: 02-04-12 15:47
Hardware & Peripheral Devices
Hardware is any physical part of the computer that you can touch.
These are pieces of hardware that are outside of the computer processor (boxy bit). These are typically connected with cables. Examples are:
A hard drive is also a peripheral even though it is in the box; this is because it is separate from the thinking part. (Avoid this example if possible, examiners are a bit weird)
Input, Output & Storage Devices (1)
Input Device: This is a piece of hardware that allows the user to tell the computer to do, for example a mouse or a keyboard.
Output Device: This is any piece of hardware that allows the computer to communicate with the user, for example a screen, printer or speakers are output devices. The screen shows pictures, videos and text to the user, the printer shows text or pictures to the user and speakers output music for the user to hear.
Storage Device: This is a piece of hardware which can store information outside of the processor (thinking bit). This information can then be put back into the processor in a form that it understands. This is important if you want to turn of the computer and then work on something you were working on beforehand when you turn it back on. It is where things are saved.
Input, Output & Storage Devices (2)
This is how hardware in a computer system usually works:
- The user inputs data with and input device to the processor
- The processor then sends it to the storage device
- The storage device then stores it
- The storage device sends it back to the processor
- The processor then does whichever calculations are required
- The processor then sends it to the output device
Input, Output & Storage Devices (3)
This diagram shows how hardware in a computer system usually works, you may be asked to draw this:
Software is a set of instructions which make the computer do something useful. These sets of instructions are combined to make programs. Programs are required to run the computer, without them they would be useless boxes.
Types of software
There are two main types of software that you will most likely be asked to explain in the exam:
Systems Software: This is sets of instructions which make the hardware work, and available for use. This includes sets of instructions which allow human beings to interact with the computer, programs that control the movement of data around the computer. For example an Operating System like Windows 7 (We will look at more information about this later)
Applications Software: Applications software is a program designed to make the computer carry out a task. It is different from systems software because it makes the computer do something useful to the user. An example of this is word-processing software, or presentation software. (Do not use brand names when referring to these as examiners spontaneously combust, call it word-processing, spread sheet etc.) Applications Packages are groups of programs, such as Microsoft Office.
Systems Life Cycle
What is the Systems Life Cycle?
When a problem is being solved it is important to follow a set of specific steps in order to produce the best solution. These steps are in a particular order so that no steps are missed out. The Systems life cycle is a set of steps that developers go through while making their software.
Steps of the Systems Life Cycle
The systems life cycle consists of these steps:
- Accurately defining the problem
- Feasibility study
- Requirements Analysis
Accurately Defining the Problem
Accurately defining the problem:
When preparing to make a piece of software it is important that the people creating the software are actually solving the job that the customer wants.
It is the Systems analyst’s job to understand the problem that the client wants solved, if they do not understand the problem then all the work into making the software will go to waste because it will not actually do what he client wants it to do.
The systems analyst will have meetings with the client to work out exactly what to do. The client has a good knowledge of the problem but not one of computers and the systems analyst has the opposite.
- This is basically just working out if it is sensible for the company to make this piece of software. It is made up of these main questions.
- Is the solution technically possible? – does the technology exist to solve the problem?
- Is the solution economic to produce? – does it cost too much for it to be profitable for both company’s?
- Is the solution economic to run? – will it cost huge amount to money to keep it running? Is it worth this expense?
- What effect does it have on people involved? – will it cut 100s of jobs? Is this the right decision?
- Is the workforce skilled enough? – will the current employees be able to work the new system?
- What effect will there be on the customer? – will the new system make it easier for the customer to receive service?
- Will the new system be economically beneficial? – will the new system make more money for the company?
This is basically a list or specification of what the software has to do. The requirements Analysis – or specification as it is sometimes called – is made by looking at the current system and seeing how they do it, and why and then making sure the new one completes the same task. These are the methods used to find this out:
Interview – find out what they want face to face, questions can be tailored to person
Questionnaires – find out what employs want
Group meeting – not always good as people act differently in groups
Observation – watch current system in action
Looking at existing documentation – looking at files that already exist
This is basically making the software. Systems flowcharts and Data flow diagrams are used. If you don’t know what they are go Google it.
This is the process of swapping out the old system for the new one. There are a couple of ways this is done:
Parallel running – this is basically running both systems at the same time. Once the new one is glitch free they can ditch the old one.
Pilot running – this is when the new system is fully implemented in one section of the business. This means that any errors will not affect the whole company. When it is working well the rest of the company will switch
Direct change – old systems removed and new one put in. No testing very risky.
Phasing – parts of the system are swapped out, until the whole system is running on the new one.
This is basically fixing it when it goes wrong. There are three types:
Corrective – fixing bugs in the systems*
Perfective – this is making things run more efficiently
Adaptive – if the problem that was being solved changes then the system can be changed to work better to solve the new problem
*The first computer bug was a moth that cause a circuit to short :D