Information Software Technology- Chapter 3

Data is the raw material entered in the computer. This raw material can be text, numbers, graphic, audio, animation and video

Data can be converted into information by; combining data, displaying it in an understandable way or removing unnecessary data

Analog or digital

• represented by using continuous variable physical quantities such as voltages
• For example, an analog clock shows a second hand continually sweeping around the clock face, measuring small units of time. At any moment the clock will give you an instant measure of the exact time, since you can estimate parts of a second as the second hand moves– The time is changing in a continuous movement

Analog signals are pulses, usually electrical or optical, in the form of continuous waves.

Is represented using discrete measurements in the form of digits or numbers. For example, a digital clock shows the time as a certain number of hours and minutes, moving in a serious of steps

Data is represented in discrete quantities using digits

• Depends on the data entered
• E.g. Data could be a measurement, however by itself the measurement does not mean anything, but when its put into an understandable format, it can provide useful information

Is valuable when it is relevant, accurate, current and well presented

It is displayed on screens, printers or speakers (hardware devices)

Information technology uses data in digital form using only two digits: 0 and 1.

The digit 0 is used to represent the electronic state of ‘off’ and the digit 1 is used to represent the electronic state of ‘on’.

Each on or off digit is called abit (BInary digiT).

Smallest unit of data stored in a computer.

8 bits

In words. A word (or word size) is the number of bits processed by the computer at one time.

• When the computer moves bits from one place to another it takes one word at a time.
• Most computers use word sizes of 8, 16, 32 or 64 bits. The bigger the word size, the faster the computer.

The decimal system consists of numbers between (0-9) e.g. The number 1 in 1969 has the value of 1000

It consists of only two digits which are 1 and 0

It starts at 1 (or 2⁰), the next heading is a 2 (or 2¹), then a 4 (or 2²) and so on up till 2⁸

Data in a computer is usually grouped using only 8 place value headings or 8 bits (0s or 1) the place values of binary are;128, 64, 32, 16, 8, 4, 2, 1

A code that represents letters, symbols and numbers as binary code

It stands for American Standard Code for Information Interchange and is used by most PC’s

• Originally a standard 7-bit ASCII was used, but it was not large enough to handle all characters used in the languages of western Europe
• Extended ASCII code was developed using an 8 bit binary code to extend the character set
• Extended ASCII is used all over the world and allows for 256 different characters

Prefixes such as kilo, mega, tera, giga are used to measure data storage

When data is collected first hand.Organisations prefer to produce their own primary data as it is more reliable but its time consuming and costly

Primary data can be acquired through surveys and interviews

A form is a document with blank spaces that need to be filled out to collect information

It is when data is collected from other sources. The issue is, it may not be accurate at the time of publication because the information becomes out of date as society changes

It is available as printed text on the internet. Printed text comes in the form of books, journals, news papers etc.

A discussion group on a certain topic.

Data in the form of letters, numbers and other special characters Word processors allow text to be entered to create documents such as letters. It is edited by deleting, inserting, moving and copying

• It is stored as ASCII codes
• File extensions include: TXT, DOC, RTF

It is a system that allows documents to be cross-linked in such a way that the user can move from one document to another by clicking on text that is linked to that document

File extensions include HTM or HTML

• alphanumeric—all keyboard characters
• numeric—numbers only (often used to perform calculations in a database or spreadsheet)
• alphabetic—letters only
• Boolean—true or false
• currency—moneydate—day, month, year

• Pictures such as drawings, paintings or photos. It is created using graphics programs or captured through digital cameras
• It is edited using graphic software by being cropped, morphed or contrasting colours

• Two main types; bitmap and vector. Bitmap is not good quality
• Aliasing– enlarging a bmp graphic and it become distorted

JPEG, BMP, GIF

• It is sound that has been digitised or represented in the form of digits 
• It is edited by deleting sounds, adding echo, increasing pitch, overlaying it or changing speed

File extensions include MP3, WAV and MIDI

• It is made up of frames displayed in a sequence which contains individual images
• It is edited by video editing software, special effects, adding text, cutting clip etc

File extensions include MOV,AVI and MPG

• It is the movement of an object which is a result of a series of graphics or frames presented in rapid succession
• Can be more useful than a picture or video as it can show things repeatedly in a simplified way e.g. How blood flows through the human body

File extensions include GIF, MOV, SWF

It involves receiving and keeping data for a long time

Primary storage stores in the CPU (central processing unit) It is for data and programs that need to be instantly accessible to the CPU

It is internal storage because it uses silicon chips located in the motherboard

Consists of RAM, ROM and cache

Random Access Memory. Data and instructions are held here temporarily. Dynamic RAM and Static RAM

Depends on a supply of electricity on the main storage, so if the computer is shut off, all the memory is lost, this is known as volatile memory

Can be accessed randomly, this means that a byte of memory is accessed with touching any other bytes

Dynamic RAM– Memory that needs to be constantly refreshed

Static RAM– Memory that doesn’t need to be refreshed. It is regarded as the working memory of the computer

Programs and files currently in use is stored in RAM

Affects computers performance, too much memory = slow computer, this is why DRAM has been invented because it constantly refreshes memory and gets rid of uneeded memory

Temporary storage area used to store data that the computer can access quickly

Cache memory– High speed memory located between the CPU and RAM. Improves performance by using SRAM

• Works the same way as cache memory. It stores the most recent data from the disk in the RAM so when the CPU needs to access data from the disk it first checks this.
• It improves performance because accessing the data from RAM is very fast.

Read Only Memory

Holds data and instructions that are fixed at the time of production and can’t be changed by the computer. It allows data to be retrieved but not entered into storage

No

Stores important programs such as booting the pc, and checking for input/output devices

Involves the use of a storage device NOT located on the motherboard

A storage device is any device that can keep data and then allow it to be retrieved

Storage devices include magnetic tapes, magnetic disks, optical disks and flash memory

Long, thin strip of plastic, coated with a thin layer of magnetic material. Modern tape is wound on two reels inside a cartridge. Data is read from and written on tape

It stores large quantities of data for a low cost, it is often used as a backup for data

Disadvantage is that it uses sequential access, which means it reads all the data from the beginning until the data needed is found

Circular piece of metal or plastic, which us coated with a thin layer of magnetic material

Uses random access to retrieve data, this means data is found directly without accessing previous data. This is very fast

Magnetic disks are mounted on disk drives. It spins it to read and write data

A hard disk is not rigid like a floppy disk. This allows it to be rotated ten to 100 times faster, which is very fast to access data

Removable cartridges are hard disks which are fast and have the best aspects of hard and floppy disks.

Zip disks– Stores up to 250 MB of data. Popular for backing up hard disks and transporting files

Jaz disks– Better version of sip disks. Store up to 2GB of data and are suited to large files for multimedia, graphics and sound

A floppy disk is a magnetic disk made of flexible plastic. They don’t store much data and are slow, but are portable and cheap. It used for storing small fires

A storage device where data is read and written using laser technology. It is reliable and stores large amounts of data

Compacts disc is a polycarbonate disk which is coated with a reflective layer of metal. Data is written to the CD with a high-powered laser that burns millions of tiny holes on the disks surface. There are many types of CD’S:

CD-ROM (Compact Disc– read only memory) which contains data that can’t be changed. It is needed to read data. Good for retaining data that doesn’t need to be changed

CD-R (Compact Disc– recordable) allows data to be corded but it cannot be removed

CD-RW (Compact Disc– rewritable) allows user to write, erase and rewrite data. It is slower than a hard disk

• Digital Versatile Disks are optical disks that can store large amounts of data. Many kinds such as DVD-ROM, DVD-RAM, DVD-R, DVD-RW
• They play movies, read DVD data disks, read computer CDs etc

An erasable memory chip used in phones and pcs, similar to memory chip

Keeps data when power is removed, data is electrically removed.

Comes in variety formats such as SmartMedia. Another type is a memory stick which is connected via USB port

• This is when data is sent one bit at time in a single line. it is used for peripheral devices such as keyboards and mouse
• It is cheaper than parallel transmission but slower

• Asynchronous transmission– Sending of data by checking each byte with special stop and start bits. It is standard for pcs. It uses and extra bit to check for transmission errors
• Synchronous transmission– When data is sent at the same rate. This means the same number of bits is sent is second. Faster and more effective than asynchronous transmission since there are no extra bits

• Sending more than one bit at a time using separate lines. Much quicker than serial transmission since is sens more than one bit at a time
• But it used for short distances otherwise errors start to occur in transmission

It is used inside the system unit to connect peripheral devices such as disk drives

Reduces the number of bits required to represent information. It allows the user to store and make data transmission faster

The amount of compression is measured with compression ratio, where the uncompressed unit of data represents the amount of compressed data, eg. 2:1 states that 2 bits of uncompressed data is equal to one bit of compressed data

Lossy compression permanently removes a number of bits from the file. The file becomes smaller in size but is not identical to the original file

• Audio and video files can be compressed with high compression ratios with no noticeable changes
• JPEG and MPEG are common file formats for video and audio compression

• Allows original file to be recovered without loss of information
• Works by replacing repeated data with something that takes up less room
• For example, replacing the word ‘and’ with a single symbol

Popular lossless compression systems include ZIP by Windows and StuffIt by Macintosh

• Information theft—stealing data from one organisation and selling it to another organisation
• Financial theft—illegal transfer of money from one account to another
• Information alteration—changing or deleting existing data
• unlawful access—unauthorised access to data in a computer system
• Burglary—stealing a computer with its data
• Vandalism—intentional damage to a computer system
• Viruses—creating or introducing computer viruses

• Choose passwords that are not obvious and change them frequently
• Use personal identification numbers (PIN) for cards
• Using biometric devices such as fingerprint devices, hand size and eyes for recognition
• Encrypting (coding) data when sending it somewhere
• Use firewalls to check incoming data and protect the system from hackers
• Discard of waste carefully, i.e shredding paper with information
• Carefully screening employees so they don't leak out sensitive information
• Always have regular backups in fireproof safes
• Digital signatures to identify people