What are the seven stages of the systems life cycle?
Feasibility Study Systems Analysis Design Implementation Testing Installation Maintenance
What must be done during the Feasibility Study stage?
The problem must be defined. Tests must be carried out to check if it is possible to carry out the project. Checks to see what hardware and software will be needed. Is it economically feasible? Is it environmentally feasible? Does it fit in with data protection laws?
What must be done during the Systems Analysis stage?
The requirements specification must be written. Details of necessary input and outputs must be written. User requirements must be specified. The hardware and software needs must be written. Facts about the company's current situation must be found.
What must be done during the Design stage?
Area that need to be considered are written descriptions, diagrammatic representations, a data dictionary, input design and program specification.
What must be done during the Implementation stage?
Programs must be produced, code will be modified and documentation stating what has been done must be produced.
What must be done during the Testing stage?
Tests must be carried out using suitable test strategies. Test data must be produced.
What must be done during the Installation stage?
A method of changeover should be decided. Staff training should be carried out. Any new hardware or software should be installed and all necessary data should be transferred.
What must be done during the Maintenance stage?
Maintenance is ongoing. Debugging of the system should take place. Any modifications should be made according to the needs of the system/company or to improve current processed.
Why is it important to define a problem accurately?
The client may not understand the potential of the computer system. The analyst may not understand or have detailed enough knowledge of the specific field that the company works in. The solution must be agreed on by both the client and the analyst.
What is the purpose of the feasibility study?
To carry out enquiries to see if there are any reasons that the new system may not be acceptable to produce.
What 6 types of feasibility must be checked?
Technical Economic Social Skill Level Legality Time
How can the analyst find facts out about the company?
One-to-one interviews. Group interviews. Collecting documents. Observations. Questionnaires. Letters, emails and phone.
What are the advantages of one-to-one interviews?
interviewee can elaborate on points clients feel like they are truly involved
What are the advantages of group interviews?
What are the advantages of collecting documents?
helps start the data dictionary
What are the advantages of observations?
first hand view of the situation
What are the advantages of questionnaires?
focused questions no need of man power
What are the advantages of letters, emails and phone calls?
What are the disadvantages of one-to-one interviews?
very time consuming
What are the disadvantages of group interviews?
What are the disadvantages of collecting documents?
not enough alone
What are the disadvantages of observations?
people act differently under observation
What are the disadvantages of questionnaires?
can be confusing
What are the disadvantages of letters, emails and phone calls?
no guarantee of QWC
What is the requirements specification?
The requirements specification constitutes the contract between the company buying a solution and the company building it. It lists what the customer expects the system to be able to do and the criteria against which the final product will be measured against to state the degree of success it has been completed to (usually success or failure.) It has to be SMART. (Specific, Measurable, Agreed, Realistic, and Trackable)
What should be included in the requirements specification?
input requirements output requirements processing requirements data structures of current and new dataflow diagrams systems flow charts requirements on which the final solution will be judged
How should be written descriptions be written?
using present terms written as an observer
What is a systems flowchart?
A system flowchart gives an overall picture of a system. It shows similar information to DFDs but also shows what hardware is used for input, output and storage, as well as what type of file is being used.
What is the design specification?
Documentation that should contain the stages necessary to produce a final end product as the designer intends.
What should be included in the design specification?
written descriptions diagrammatic representations data dictionary input design output design program specification
Why is it important to evaluate the system?
Client: needs to be sure the system will perform as required it identifies areas where the solution is lacking Analyst: determines the end of the job determines their pay also determines future steps eg, court case or payment
What criteria would be used for the evaluations?
suitability effectiveness usability maintainability
What questions could be asked in the evaluation?
• Are there any bugs in the system? • Are the users finding it easy to use? • Have the uses got adequate training and retraining? • How are the help facilities working?
What are the two types of documentation?
Technical and User
What should user documentation include?
Input/Output processes Index/contents Glossary of terms used Backing up/Archiving procedures Error possibilities FAQ Maintenance of files Required hardware specifications Help facilities
What types of help facilities are there?
Onscreen Internet-based Paper-based
What is technical documentation?
The documentation that describes how the system actually functions.
What is the purpose of technical documentation?
To assist a technical professional in the future with maintenance
What will technical documentation typically contain?
• The requirements specification • The hardware and software specification • All of the document from the design specification, including any program specifications • How to configure the system for different computer set-ups
What are the four types of implementation?
Parallel running Pilot running Direct changeover Phased
What is parallel running?
The new system is run alongside the old system. Both systems operate together. This allows the new system to prove itself before the old system is abandoned - data generated by the new system can be compared to data generated by the old system. It also means that staff can be trained and gain confidence in the new system
What is pilot running?
The new system is run alongside the old system, but only a portion of the data is actually used in the new system. This method is less of a drain on resources. Data from part of the new system can be checked with the old system, but you cannot check how the whole system will react until you have got the whole system up and running.
What is direct changeover?
The old system is stopped and the new system is started. This might happen over a weekend, for example. If something goes wrong with the new system, then it has to be sorted out because you cannot fall back on the old system. Staff training needs to take place in advance with this method.
What is phased implementation?
Parts of a new system completely replace parts of an old system, whilst the old system continues to be used as required. The part of the new system that has been installed can be used for staff training and can prove itself before the next part of the installation takes place. This method takes longer than the direct changeover method.
What is maintenance?
A term used to describe changing a system after it has been designed, installed and has been running for a time.
Why may maintenance be required?
1. A user has discovered a bug in a program. This needs to be rectified. 2. The law has changed. The system needs to be changed to ensure that it conforms to the new law. 3. New technology. The system needs to be modified to take advantage of these new opportunities. 4. A new function is needed. The company decide they would like the system to do something that it can't do so the system needs modified. 5. The business has 'outgrown' the system. eg. needs to be able to handle far more data than it used to do
What is a prototype?
A prototype is an early sample, model or release of a product built to test a concept or process or to act as a thing to be replicated or learned from.
What is the RAD approach?
It involves building a series of prototypes. After each one is built, the user is involved. They are asked to try out and comment on features and test some of the functions. Their comments are then fed back into the next prototype and a better one is produced. This process is repeated until the product is finished.
Name 5 generic applications.
Word processing software Spreadsheet software Database software Presentation software Drawing software
What is off the shelf software?
Pre-written software that can be readily bought. It will have been thoroughly tested and so wont have many bugs. There will be lots of online support or help books/guides.
What is open source software?
Software that has been developed by volunteer programmers with the intention of making available free-to-use applications with the source code available to its users. No cost. Can be adapted.
What is custom-built/written software?
Software written specifically for the needs of a company/individual by a programmers. The company will get exactly what they want however it can be expensive in both time and money.
What is a knowledge based system (expert)?
Where all the expert human knowledge covering a particular topic is brought together and made available to the user through a computer system which uses the facts it has been given in order to answer a question.
How do you set-up a knowledge-based system?
experts are interviewed information must be collected from many sources the info is used to create the knowledge system rules are used to interrogate the knowledge of the system HCI is set up to provide communication to the outside world
What are the 4 components of a knowledge based system?
Knowledge base Rules Base Inference Engine Human Computer Interface
What is the knowledge base?
contains the information supplied by experts
What is the rules base?
contains the rules that can be applied to the knowledge
What is the inference engine?
This uses the rules and searched through the knowledge base
What is the human computer interface (HCI)?
Allows for queries to be input by a user and for an output to be displayed.
What is a diagnostic system?
These are systems that ask a question, the answer given by the user resulting in the knowledge base being reduced in size. eg. A medical diagnostic system
What is an advice-giving system?
In this kind of system, a process is monitored by the software. When the software detects particular situations, it gives advice! For example, a stock control system.
What is a decision-making system?
Decision-making systems are essentially advice giving system that has enough information and the hardware and software to allow them to actually take decisions themselves, without human intervention.
What are the advantages of expert systems?
- can’t replace human intuition and hunches so no bias -can be a substitute for situations where it is impossible to recruit highly trained individuals -cheaper than the equivalent human
What are the disadvantages of expert systems?
-cannot evaluate new situations like a human can -can be expensive/difficult to maintain hardware and software -have to train people to use system -may contain system bugs
What is an operating system?
A piece of software that looks after the management of a CPU-based system.
What jobs does the operating system do?
What are the three types of operating system?
What is a single user os?
An os that allows only one user access to a system at one given time.
What is a multi user os?
An os that allows multiple users access to a system at one given time.
What is a multi-tasking os?
A mutli-tasking os allows lots of users to share data and resources at (apparently) the same time using a server. To do this, the server needs a special piece of software called a Network Operating System, or NOS. This gives the server the tools, amongst other things, to control communication on the network, for example.
What is batch processing?
Batch processing, then, is a way of improving the efficiency of a computer or network's resources by bringing together similar work and processing them all in one go at a time when resources aren't needed.
What is speed mismatch?
This is where two devices that need to work together are working at two different speeds.
What is offline processing?
This removes the need for relatively slow input devices. Instead, data is stored in files on a high-speed data storage device.
This is described as offline processing because the main computer doing the processing is not immediately controlling and reading the data from its input devices. The data is being prepared and stored away from that computer on a high-speed storage device and is then made available as necessary.
What is key-to-disk data entry?
A 'modern' key-to-disk system might be employed by an organisation to do just this because it has to transfer lots of details held on paper forms into a file so that the data can then be processed later. This system might work as follows:
- A team of data entry operators key the data on the paper forms into a temporary file on the computer.
- As the data is entered, it is validated to ensure that only sensible data is entered into the system.
- Data is stored on disk after it is validated.
- The same paper forms are passed to a second operator who re-enters the data.
- The data is then verified. As the second operator types in the data, it is compared to the data held in the temporary file typed in by the first operator.
- If the data is not the same, an error is reported to the operator. They will then investigate and correct the problem.
- If the data is the same, it is accepted and can be made available to the batch processing system.
This key to disk system, with its validation and verification techniques, will pick up most errors in data input but it is still possible for incorrect data to be put into the system.
What is a batch totals?
This is a method used to ensure that the integrity of a set of data is maintained when it is entered into a computer system.
Calculated by a human.
Before an operator enters a set of data in the system they calculate a number known as the ‘batch total’.
This is worked out by adding up the total number of data items to be entered. This ‘batch total’ is then entered along with the data.
Once the codes and the batch total have been entered, the batch total is re-calculated automatically by the computer.
It is then compared to the original batch total entered by the operator.
If they are the same, then the data’s integrity has (probably) been maintained.
If they are different, then the operator may have missed out a product code or may have entered a code twice accidentally.
The computer system would then generate an error message to highlight the problem to the operator.
What is a control total?
A control total might be calculated by using the algorithm ‘add the first numbers of all data entered’). This would give 2 + 3 + 7 + 6 + 6 = 24. The operator would then enter not only the data but also the batch total and the hash total. The computer, once all the product codes and the batch and control totals were entered, would recalculate the batch and control totals automatically.
. If they differed to what the operator entered then an error message would be displayed on the input screen. If the data consisted of words rather than numbers, then the characters in each word could be converted into numbers using their ASCII equivalent codes. These can then be used in a suitable algorithm to generate a control total.
What is a check sum/digit?
This is simply a number produced by adding up all of the individual pieces of data. When the receiving computer gets the data and the check sum, it recalculates the check sum and compares it to the check sum it received. If they are different, it means the data was sent incorrectly. The receiving computer can then signal to the sending computer to resend the data.
Calculated by the computer.
What is data consistency?
The terms data consistency refers to the ‘correctness’ of the data. Meaning that the data is correct in every instance is it stored.
What is data integrity?
The phrase ‘data integrity’ refers to the whether the data already in a computer has been corrupted after some processing has taken place on it. If data is corrupted, it will lose its integrity.
What is real-time processing?
In real-time processing. The length of time a program takes is important, as is the way that the CPU deals with instructions.
Most real time applications can be found in booking systems or in control applications.
This processing method is used when it is essential that the input request is dealt with quickly enough so as to be able to control an output properly. The is called the 'latency'.
What is important in good interface design?
- form of output
- volume of data
- colours uses
- experience of the operator
- operator disability
- hardware choices
What does compression software do?
It reduces the size of files by cutting out much of the duplication of the data stored but maintains the contents of the file.
What is a utility program?
A systems program designed to perform a commonplace task
Give some examples of utility programs.
What is a text editor?
A text file is a file that contains pure data, pure ASCII, without any formatting codes (such as the hidden formatting codes that make a word underlined, bold, in italic, right-hand justified and so on) or an actual program. A text editor is a program that allows a user to enter or edit text files
What is disk formatting?
When you 'format a disk' the utility checks that the disk can be written to and then divides up the disk into areas, giving each area an address. It then sets up a table that will keep track of what is stored in each area as well as areas that, for example, have become corrupted and cannot be used.
What is disk maintenance?
A utility is provided in operating systems to check to see if there are any problems areas on a disk and to try and fix them.
Sometimes, an area isn't big enough to hold the whole file so a number of areas have to be used. If lots of areas are used to hold one file and those areas are scattered all over the disk, then retrieving a file can be slow. If your computer has become sluggish, one reason might well be that your hard disk has become fragmented - so defragment it!
What is a back up utility?
This utility is included in most systems to allow a user to make a copy of files. If the original is damaged, then the back-up can be used. Network Operating Systems software might come with quite sophisticated backup utilities that enable the contents of the server's hard disk to be transferred to magnetic tape in the middle of the night. In the morning, the Network Administrator would then remove the magnetic tape and put it in a fire safe.
What is a system use utility?
It is often possible for a user to get some statistics from the operating system about how much RAM the system has got, how much hard disk space is available for use, what software drivers are installed and so on. This is possible because a 'system use' utility is available that can examine a computer system and display what it finds.
What is a screen saver?
Screen savers are moving pictures that are displayed on your monitor after a set period of time.
The original purpose of them was to prevent a 'ghost' image of whatever was on a screen being burnt permanently into the screen of the VDU, if the VDU happened to be left on for a long time.
Screen savers nowadays have an extra feature. They can be password-protected. If you leave your computer alone for a period of time, a password-protected screen saver can be set to come on to prevent prying eyes from accessing your computer. Although it is not a robust form of defence, it can stop casual access.