Computer Science A Level 1.1.3 Input, Output and Storage
Kilobyte (KB)
1024 Bits
Terabyte (TB)
1024 Gigabytes
Megabyte (MB)
1024 Kilobytes
Gigabyte (GB)
1024 Megabytes
3D Printers
3D printers print 3D models, using a process called additive manufacturing or AM. This process uses computer control to lay successive layers of material to build a 3D model. Two plastics, ABS (Acrylonitrile butadiene styrene) and the more eco-friendly PLA (polylactic acid or polylactide), are the materials most commonly used, but the technology has advanced to the point where almost any material can be printed with, from food to metal - although not necessarily at home.
Nibble
4 bits
Byte (B)
8 bits
Camera based readers
A camera based imaging scanner uses a camera and image processing technology to decode a 1D or 2D barcode. An imaging scanner can read a barcode on any surface, printed or on-screen, and can also read a code that is damaged or poorly printed. They are used in multiple applications such as: Age verification by scanning a driving license Coupons - A 2D barcode coupon is emailed to a customer which can be scanned from their phone. Unique codes are used so that tracking coupon usage is easy Event ticketing Consumers can also use a smart phone to scan a QR code which could be used to: Display a catalogue of movies or DVDs Play an Mp3 when scanned Display nutritional information about a product
What is a byte?
A group of eight bits is known as a byte.
Mice
A mouse is a pointing and selecting device used with graphical user interfaces (GUI). There are different kinds of mice around, each with their own advantages and disadvantages although they all broadly do they same thing: point and select.
What is a nibble?
A nibble is a group of 4 bits. The smallest value a nibble can hold is 0000 in binary and the largest number is 1111 in binary.
Nibbles and Bytes
A single bit cannot hold a great range of numbers. It can hold either a zero or one. A nibble is a group of 4 bits. The smallest value a nibble can hold is 0000 in binary and the largest number is 1111 in binary. (0000 in binary is the same as 0 in denary. It is also very common to group bits together in groups of 8. A group of eight bits is known as a byte.
Touch Screens
A touch screen enables a user to touch their Visual Display Unit (VDU) screen to make selections. A user makes a selection by touching the screen with their finger. Touch screens allow very fast selections from choices. They could be used in places where people need to find out information but may have zero computer skills, for example, an information system in a library or a museum. They would be of limited use if you had to type in a letter, for example.
Video Graphics Card
A video is made up of a series of frames, that are played quickly enough to appear moving. A video capture card is a piece of hardware that is plugged into an expansion slot inside a computer. A user then attaches a video camera or TV, for example, to the video card. When the video or TV is played through the card, the analogue signals that make up the moving picture from these devices are converted into digital images, frame-by-frame.
Actuators
Actuators are motors that are commonly used in conjunction with sensors to control a mechanism. For example Opening a window or valve Starting or stopping a pump. Turning a wheel. Controlling a device in a smart home.
Output Devices
An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by a computer system, that converts the electronically generated information into human-readable form.
What is an output device?
An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by a computer system, that converts the electronically generated information into human-readable form.
SRAM
As long as there is power SRAM will hold the data. Data can be read to and from SRAM.
Automatic Input Devices
Automatic data input methods are methods where data is collected and processed and prepared beforehand in some way so that it can be directly entered into a computer system when needed.
Bar code
Barcodes are made up of black and white lines. The lines represent data in coded form. The data held in a bar code can be retrieved by using a laser scanner. The data obtained can then be used to look up further information held on computer. Bar codes can be attached to libraries to speed up taking out and returning books. Membership systems that require members' details to be retrieved could employ barcodes. Supermarkets can use them to speed up the checkout process and to produce itemised receipts. Bar code systems have built in validation techniques that greatly reduce errors. The data scanned can be integrated into management information systems so that, for example, managers can tell which books are never taken out of a library and should be removed, which members never attend an event or which products in a supermarket sell best on Sundays. In supermarkets, bar codes are an integral part of the stock control system. One problem with any system that is completely reliant on computerised systems, however, is what to do when the system breaks down. A bar code for a product in a supermarket will typically contain: the country of origin of the product the manufacturer's identity number the code for the actual produc the check digit, used to check that a number has been scanned in correctly.
Biometric Devices
Biometric devices means using a unique part of your body to identify you. Typical examples include fingerprint scanning in canteens, libraries, phones and ATMS, retinal (eye) scanning for access to buildings and biometric data held in a chip in newer passports. Biometrics are very convenient as you can't lose or forget a finger or your eye like you can a card. It also reduces the need for cash to be handled, which cuts down on costs and removes security issues. There is an ever-present threat of hackers stealing your data and using it for unauthorised or illegal activities.
Magnetic Stripe & Smart Cards
Data can be entered into computer systems by using cards that have a magnetic stripe on them. The magnetic stripe holds coded information. This can be retrieved by 'swiping' the card through a magnetic card reader. The information can then be used directly, or used to retrieve more information from a central computer. This type of data input is typically used for credit cards, debit cards and loyalty cards. They are quick to use, can be used many times, are cheap to produce and the important information held on them cannot be read unless you have the right equipment. Magnetic stripe cards can be read but not written to. The data is placed on the card when it is made. For this reason, smart cards have become more widely used. These are cards that have an electronic chip on them. This can be used to record each time a transaction occurs, for example. In other words, smart cards can be written to as well as read from. Interestingly, cards with magnetic stripes typically have some details written on the card as well so that a person can read them. It might have the name of the owner of the card on it, in case the card gets lost. It might have the card number on it, in case the owner of the card wants to use it to buy something over the Internet or phone.
Uses of Hard drives
Hard drives can be used to store operating systems, programs and user files. They are also a good backup device
Digital Cameras
Images are stored digitally. The images are then transferred to a computer. The amount of memory is a very important consideration with these cameras, as is the ability to add memory using a memory card. This is because storing images is storage intensive. Cameras often allow the user to select between high resolution and low resolution modes. If you use a high resolution mode, you will be able to take fewer pictures than low resolution mode
Where is the bios held
In the ROM
What two things does the bios do
It checks that the computer hardware is present and working It runs a routine that looks for a program called the bootstrap program. When it has be found it loads it into the ram and runs it
What is the bootstrap program's job
It is to locate the OS on the hard drive and then load it into ram and run it
LCD (Liquid Crystal Display) Monitors
LCD (Liquid Crystal Display) Monitors These contain groups of red, green and blue diodes to form each pixel. The screen is typically back-lit using LEDs (Light Emitting Diodes).
The advantages of Organic LED (OLED) screens
Made of plastic rather than glass so flexible Thinner than LCD/LED Bright without the need for backlighting Consume less power which is good for portable devices (eg smartphones) Fast refresh rate (good for video games) Greater depth of colours Better viewing angles
Manual Input Devices
Manual input devices means a human operator must use the device to input data into a computer system.
Types of Mice
Mice with a scrolling wheel to allow you to better navigate applications and web pages. Optical mice that aren't prone to collecting fluff and dirt and so don't need cleaning. Mice that use radio waves to connect to the computer instead of wires, so that there is less clutter on the desk. Ergonomically designed mice, for example, mice that are very small for the small hands of children. Mice that can work with a serial port, a PS/2 port or a USB port.
Visual Display Units (VDMs)
Monitors are ideal for displaying data and information to users. They come in a range of sizes. Larger ones such as 21-inch screens, for example, would be ideal for engineers using Computer Aided Design software applications. 15-inch screens are perfectly acceptable for users using a range of generic applications. Old CRT (Cathode Ray Tube) monitors take up a lot of space on a desk. Flat panel liquid crystal display screens, often referred to as TFT screens, save a lot of space by comparison. They are not quite as sharp as CRT screens, however, and are more expensive. TFT screens produce less radiation than CRT monitors. Excessive exposure to radiation is seen as a potential risk to computer users. TFT screens use about half the power a CRT screen uses.
Standard Keyboards
Most computers have QWERTY keyboards. These can be used to enter in data manually. A lot of work has been done to ensure that keyboards are designed ergonomically. There is a health and safety problem known as Repetitive Strain Injury (RSI) for people who use keyboards all the time.
Optical Devices
Optical devices store binary patterns using lasers. The lasers shine onto a disk and change whether an area on it can reflect light or not. The laser can then be used to read back patterns by looking at which areas reflect light and which don't
Optical Mark Readers
People put marks in set places to indicate a choice. They are used, for example, in multiple-choice tests because the answers can be scanned in and a student's mark calculated by the computer - less work for the teacher. They can be used to capture answers to questions on a questionnaire, or to select numbers on a lottery ticket. Some applications are not suitable for OMR. For example, you wouldn't collect names using OMR because you would have to provide 26 places for a mark to be made for each letter in the name. When OMR sheets are completed, they can be scanned in automatically and the results produced straight away.
Plotters
Plotters are widely used in some industries. They are used to plot large drawings such as those needed by engineers and designers whereas standard printers commonly print up to A4 (and sometimes A3). Plotters produce very high quality, very accurate, colour drawings. they are relatively expensive compared to printers.
Radio Frequency IDentification (RFID)
RFID refers to small electronic devices that consist of a small chip and an antenna. The chip typically is capable of carrying 2,000 bytes of data or less. It serves the same purpose as a bar code or a magnetic strip on the back of a credit card or ATM card; it provides a unique identifier for that object. And, just as a bar code or magnetic strip must be scanned to get the information. A significant advantage of RFID devices over barcodes is that the RFID device does not need to be positioned precisely relative to the scanner.
Examples of Solid State Drives.
SD cards, micro SD cards and pen drives.
Bit
Smallest Unit
Solid State Drives
Solid State Drives have no moving parts. That means they can't get worn out and are not as easily damaged by bangs and knocks as optical and magnetic devices.
What are the two types of RAM
Static Ram Dynamic RAM
What are the disadvantages of Virtual memory
Takes longer to access data from secondary storage than main memory so it will take longer to access data Constant swapping of pages between main memory and secondary storage can slow the computer down
Bits
The basic building block of any computer is the switch. Computers, however, have millions of electronic switches in them, held in components such as RAM or the processor. Each switch can have one of two positions, on or off, which in computing, we represent as 1 or 0. Each switch can therefore hold one simple piece of information (1 or 0) and we call each switch a bit (from Binary digIT). It is the smallest unit of storage or memory.
Speakers
The cheapest option is simply a pair of speakers powered by the computer. They will plug into the back of the computer, in the speaker output. The quality and level of sound will be perfectly adequate for many applications but they cannot produce a very loud output and cannot produce a very high quality sound. You could also buy a pair of speakers that come with their own power supply. Although more expensive, they produce a higher quality sound and greater volume. It is perfectly possible to connect an amplifier to the back of a computer and then pass the amplified signal to some speakers. This is a much more expensive proposition but does produce hi-fi quality sound. In some noisy environments such as factories, sirens are common. These can be computer controlled and can produce a very loud sound that can be heard over noisy machinery.
Headphones
There are situations where a user wants to listen to sound in a public place but doesn't want to disturb others. For example, a user in a library might want to listen to CDs on a computer, or a telesales operator might need to concentrate on what a customer is saying.
Dot Matrix Printers
These are relatively slow and noisy and the quality of the print out is relatively poor compared to inkjets and laser printers. They were very common in the earlier days of computing. Their uses are far more limited now but they do have one particular advantage. The hard copy is made by pins striking paper. That means that identical copies can be made of a printout by using carbon paper between sheets of paper. This system is used by credit card companies to produce actual copies of receipts when a customer makes a purchase. After a customer's credit card is swiped and authorised, two identical copies of a receipt are printed using small dot matrix printers. Both copies are then passed to the customer, who signs the top copy. This puts a carbon signature on the bottom copy. The customer keeps one copy and the shop keeps the other. You cannot make actual carbon copies with inkjets or laser printers although of course you can print out two copies of a document.
Organic LED (OLED) screens
These are thinner, brighter and lighter than LCD or LED screens. The screen is plastic rather than glass and is flexible. In the future these may be used for pages in electronic books or magazines, paintings on walls or even in clothes.
Graphics Tablets
These are touch-sensitive pads that allow you to 'draw' on them with a stylus. The pressure from the stylus on the pad is sent to the computer, which reproduces what was done on the pad in a drawing program or Computer Aided Design (CAD) program. These types of data input devices are far more natural for designers to use than trying to use a keyboard and mouse to draw with.
Magnetic Devices
These store binary data patterns as billions of magnetised areas on a disk. These areas can be read or written to by a special head that moves over the magnetic area
Touch Sensitive Keyboards
These types of keyboard have 'keys' which are made up of touch-sensitive areas on a plastic cover. A user presses on the touch-sensitive area to input data into the computer. They have a wide range of applications. They can be used in fast food restaurants. Operators simply press on pictures on the keyboard. This speeds up data input and means that training needs are minimal. Dirt can get into normal QWERTY keyboards and cause them to malfunction but the protective plastic cover on touch-sensitive keyboards stops this happening. They can be used to customise keyboards because some touch-sensitive keyboards (called 'concept keyboards') allow you to program what you want to happen when an area is pressed.
Laser Printer
These types of printers are in widespread use. A laser printer produces very high quality black and white hardcopy. It costs more to buy and run than ink-jets although costs have been steadily falling in recent years. The price of colour laser printers has been falling to make them within reach of individuals and small businesses. Refills are expensive compared to inkjets.
The Advantages of LCD (Liquid Crystal Display) Monitors
They reach max brightness almost immediately Sharper image with realistic and vivid colours Brighter light Thinner in construction Last a long time meaning they are reliable Consume very little power
What is virtual memory
This is when the computer uses some of its disk space as if it were ram due to their not being enough ram to keep up with all the tasks that are running
DRAM
This needs data to be refreshed periodically this means it needs to have extra circuitry and this has implications on the amount of power DRAM needs to run
Inkjet Printer
This type of printer 'sprays' ink onto paper. An inkjet printer can't produce carbon copies. It can produce very high quality black and white as well as colour copies for a very low cost. It is a good choice for low volume applications such as small businesses or homes.
What can a camcorder do?
Typical features of digital camcorders include the ability to zoom in, record sound, view films through a viewfinder, some have night viewing capabilities, time-lapse photography, picture stability software and special effects.
Scanners
Typically, the image is placed on a flat screen. The image is divided up into pixels by the software. The user can tell the software what resolution to use (how many pixels per square centimetre to split the picture up into). The higher the resolution, the better the detail of the image but the bigger the file. A light is passed from one end of the scanner to the other, so that it passes over the image. When the light hits each pixel, it gets reflected back. Each pixel's information is stored. The information about all of the pixels is used by the software to reconstruct a bitmap image of the picture. Because bitmaps are large files, they are often compressed. Different file types use compression, such as GIF files or JPG files.
Voice Recognition
Using a microphone and some appropriate software, it is possible to input data into a computer or directly into a tablet PC or phone. The software is not perfect. You often have to teach it to recognise your voice accurately. If you have a cold or a throat problem, or a very strong accent, it may reduce the accuracy of input.
Webcams and Microphones
Webcams capture the image in front of them whereas microphones capture sound. They are typically used for VOIP applications (Voice Over Internet Protocol) such as Skype, where two people can communicate over the Internet using a camera and a microphone. These kinds of devices are excellent for families and friends to keep in touch and for businesses to communicate instantly across the globe, saving the time, energy and expense of travelling.
What you can do with a digital camera?
You can immediately view photos and re-take or overwrite them if they are not what you want. You can often add extra information easily, such as the date or information about the photo. Images can easily be distributed to friends via email or social networks. Images can be opened in a graphics package and manipulated. They can be cropped, colours changed and parts of the photo 'touched up', for example.
Camcorders
camcorders, are cameras that store moving images. Some camcorders store the moving images as analogue signals. You may have heard of VHS. Analogue camcorder films lack really mint quality and lose quality if they are copied. Films made using digital camcorders, on the other hand, have much better quality and don't lose any quality if they are reproduced. This is because the films are stored digitally. Digital Video (DV) is a common digital format.
1 Kilobyte (1KB)
is 1024 bytes exactly, or 210 bytes exactly, or about 1,000 bytes, or about a thousand bytes.
1 Megabyte (1MB)
is 1048576 bytes exactly, or 220 bytes exactly, or about 1,000,000 bytes, or about a million bytes.
1 Gigabyte (1GB)
is 1073741824 bytes exactly, 230 bytes exactly, or about 1,000,000,000 bytes, or about a thousand million (a billion) bytes.
1 Terabyte (1TB)
is 1099511627776 bytes exactly, 240 bytes exactly, or about 1,000,000,000,000 bytes, or about a million million bytes.
What are the advantages of Virtual memory
Enables computers to continue function even though it has run out of Ram most commonly used files will continue to reside in main memory for speed of acess
