ASCII code system:
The ASCII (American Standard Code for Information Interchange) system uses binary decimals to represent different characters. Each digit takes up memory of 1 bit; it takes 8 digits i.e. 8 bits i.e. 1byte to form a character. 1024bytes (210 bytes) = 1KB; 1024KB (220 bytes) = 1MB; 1024MB (230 bytes) = 1GB etc different combinations of any 8 bit forms a character. ASCII includes most if not all symbols, including intangible ones eg Del, Space etc
Hexadecimals:
Hexadecimal is used in computing when there are too many digits for binary decimal. Eg 255 have 8 digits in binary but only 2 in hexadecimal. It is used for large value numbers such as in the case of html colour panels.
Hexadecimals are 16 digit based; 10 – 15 is replaced with A – F respectively. To convert decimal to hexadecimal or hexadecimal to decimal uses the same method as binary conversion, but 16 based.
Eg converting 1980 into hexadecimal
1980 = 162 x 7 + 161 x 11 + 160 x 12
Therefore 1980 in hexadecimal is 7BC
Eg converting 15FA into decimal
163 x 1 + 162 x 5 + 161 x 15 + 160 x 10
= 4096 + 1280 + 240 + 10
= 5626
Therefore 15FA in decimal is 5626.
Social and Ethical issues:
Health of human body can be affect through use of information systems. The study of human body and technology is referred as ergonomics. The following are a few health problems the can arise form the use of information system:
Tools for information process –
Collecting:
The collecting process involves deciding what to collect, where to collect form and how to collect.
Hardware for collecting different data
Text – keyboard, text scanner, voice recognition
Numbers – bar code readers, data loggers, keyboard
Images – scanner, web cam
Video – video recorders, digital cameras
Audio – micro-phone,
Software for collecting different data
Text – Microsoft word
Numbers – Microsoft excel
Images – scanner software
Video – windows media player
Audio – Sound recorder
Organizing
Text – as explained before texts are converted into binary decimals to be processed by other processes, e.g. displaying, analysing etc. Examples of file types: word document, HTML, PDF
Numbers – Like text, each numerical number can be converted into a binary number. Common file type: excel, word document
Images – An image is an electronic copy of a picture, photo, scanned document etc for display on screen. All images are made of pixels, which are the smallest controllable display element on most screens. There are two types of images:
Bitmapped: each pixel is treated individually and represents bits in memory. Their size, colour, tone etc is stored and therefore takes up large amount of memory. The most common bitmapped file types are BMP (high quality images), JPEG (less memory, lossy compression method) and GIF (maximum 256 colours for cartoons, lossless compression by less colour and smaller size).
Vector: end points containing information about the line (thickness, colour, gradient etc) common type of file is PNG, but not supported by early versions of internet explorer.
Audio – Series of sound measurements. Digital samples are created from real sound waves. The higher frequency of taking samples and the more accurate they are, the better the quality, but the larger the file. Common file types are MIDI and waveform (MP3, MP4 etc).
Video – A series of still images recorded at high speed, usually along with audio. Hugh in file size. Common file types include animated GIF, MPEG, Flash etc. data is organized using key frames, one for each image that forms a video/animation when played
Analyzing:
An example of analyzing data is creating a chart in a spread sheet. Charts and graphs are the most popular ways of analyzing data. They show relationships, trends and comparisons at a glance. The impact (use of colours and symbols to draw attention to important data), speed (obvious) and simplicity (easily understood) made it popular. E.g. software excel, calculator
Saving and retrieving:
Saving and retrieving is important because it allows edited data to be stored and edited later on. Most information systems have a primary storage and a secondary storage.
Primary storage is used to store data/information that needs to be instantly accessible to the CPU. It uses silicon chips on the motherboard to store.
RAM random access memory, where frequently used data/information and instructions are stored. When the power is cut off everything in RAM disappears. Data are accessed directly without going through other things.
Cache is another example of primary storage. It has the same functions are RAM, but is temporary storage for quick access.
ROM read only memory, permanent memory where instructions are stored. These instructions are not to be edited or it may distract the processing of the computer. These instructions are applied when ‘booting’ the computer.
Secondary storages are usually portable.
Magnetic tape: long thin plastic coated with thin layer of magnetic metal. Magnetic tape can store large amount of data for a cheap price and little space. However it uses sequential memory access, which takes a lot of time. e.g. video tape. Good for back up.
Magnetic disk works the same as magnetic tape, but with a circular piece of plastic/metal. E.g. hard disk / floppy disk. Uses random memory access.
Optical media uses laser technology to read and write on CD, CDR or CDRE. Written with high power laser to create lots of tiny holes on disk.
Flash memory is erasable memory chips e.g. USB, SD card, memory stick etc.
Processing:
Examples of processing software: audio editing programmes, movie maker, video editors
Transmitting and receiving:
Buses and ports are used for transmitting and receiving. Buses are connections between CPU and other parts. Ports are sockets that allow an external device to be installed. E.g. e-mail is transmitting and receiving mails.
Displaying
Printer, monitor speakers etc. most monitors are displayed in pixels. Number of pixels on the screen can be adjusted.
Planning, deigning and implementation
Understanding the problem
This is the first stage of developing a system. It involves identifying the problem that needs to be solved and determining the requirements of the new system through surveys, interviews, analysing existing system, investigation, research etc. Draw up a project plan, specifying who, what how, when; consisting grant charts, schedules, dataflow diagrams, journals, plans etc.
Making decisions
Determine the feasibility (is it possible) of this new system, analysing potential solutions and makes a recommendation. A feasibility study shows:
- nature of problem and overview of existing system
- identifying problem
- outline constraints (economical, cost vs. benefit; technical, technology requirements and demands; schedule, time wise; organisational, fitting the goal of organization)
- restates aim of new system in detail
- analyse data collected
- suggest solution – no change, new system, investigate etc
Designing solution
Diagrams such as data flow diagram or system flow chart are used to show context of new system.
Data flow diagram is a graphical way of showing the flow of data within the system. ○ process, □ external entity, 〔 Data storage, ↗ data flow.
System flow chart shows both flow of data and logic of system. Terminals, input/output, process, database, decision, flow line.
Decision trees show all possible decisions and their results.
External specification – the appearance of new system
Internal specifications – providing technical support to build the system, identify process required by new system, specifications for input data.
Information technology – application software may be available e.g. existing accounting softwares. If not then programme has to be written and meets the exact needs of new system.
Technical specification – new hardware support need or not.
User documentation – user manual for new system. Must be user friendly.
Implementing
This is the stage of applying the new system. There are three ways of converting to the new system:
- Direct conversion – where the new system is completely replacing the old system. Does not allow time to check that the new one works correctly, old system is erased.
- Parallel conversion – the new system and old system is run at the same time to allow room for error.
- Phrased conversion – gradual implementation of new system. Certain new ones are implemented while other old ones are still operation. Each operation is individually tested.
- Pilot conversion – when a small part of the organization uses the new system. If new system fails, old is there to back it up.
Training is needed to teach participants to use the new system. The participants include those who are learning and those who are teaching. Who needs to be trained is decided upon their existing knowledge.
Testing, evaluating and maintaining
System needs to be tested to ensure that it runs correctly. Results are compared to expectations and initial aims. Determines if change is required. Occurs after minor adjustments.
Evaluation is the ongoing process of assessing the system to identify areas of weakness that needs to be changed.
Maintaining is the modifying of system after installation, upgrading by making minor improvements.
