MICROPHONE/SOUND CARD
SOUND CARD- A sound card allows a personal computer to play speech, music and other sounds. A sound card can also be used to capture sound, music and speech from a variety of sources.
VOICE RECOGNITION- The facility to control a computer program or carry out data entry through spoken commands via a microphone connected to a sound card.
MULTIMEDIA- A combination of several media under the control of an interactive computer program including text, graphics, sound, video and animation.
VoIP (VOICE OVER IP) - A relatively recent technology that enables users to make and receive telephone calls via the Internet. Example is Skype.
DIGITAL CAMERA
DIGITAL CAMERA- A digital camera captures and stores still images in a camera’s memory until they can be transferred to a personal computer. The image is recorded using a charge-coupled device which recognizes the different colours and intensity of light in the image.
DIGITAL VIDEO CAMERA- Digital video cameras can be used to record motion video sequences at high quality. Since images are recorded digitally, they can be transferred to a personal computer, edited and then output to another device without any loss of quality.
The individual dots that make up an image are known as ‘pixels’. Early digital cameras were only able to capture images at a size of 320 by 200, giving
WEB CAMERA
Web cameras (webcams) allow the real-time capture of images and sound; the information is usually compressed so that can be transmitted via the internet. This enables three basic applications:
1) Video e-mail (v-mail) involves sending an e-mail message to which a video clip has been attached.
2) Video conferencing allows a group of users to communicate with each other simultaneously.
3) Webcam monitoring involves setting up one or more webcams to watch a given person or place. As an example, a number of static webcams continuously
broadcast images from NASA. A webcams can also be used to replace a CCTV system.
MICR
MAGNETIC INK CHARACTER RECOGNITION (MICR) - Capture and recognition of data that have been printed using a special magnetic ink. Some of the details on a cheque, such as the cheque number, are printed in a special typeface using
magnetic ink.
SELECTING INPUT DEVICES
The selection of an input device is usually based upon three basic criteria: volume, speed and accuracy.
VOLUME
SPEED
If large volumes of data need to be entered, speed and accuracy may be
important considerations for many business applications. OCR and OMR can be many thousands of times faster than manual data entry methods.
ACCURACY
In same business applications it is essential to ensure that data entry is completely accurate. For example, in engineering. In many cases, it may be acceptable if an input device generates a certain number of errors. This is often referred to as the error rate.
ERROR RATE- The frequency of errors which occur when using an input device to recognize patterns.
OTHER CRITERIA
Other considerations when selecting an input device might also include:
-Complexity of data -Cost
-Frequency of data entry.
OUTPUT DEVICES
Output devices display the results of computer processing.
DISPLAY DEVICES
The most common output device is the monitor that is attached to all personal computers systems. The older, television-style monitor is sometimes referred to as the visual display unit (VDU) or CRT (cathode ray tube).
The quality of a monitor’s display can be described in several ways:
1) Resolution. The resolution of the monitor describes the fineness of the image that can be displayed expressed as number of pixels (picture elements) - the individual dots that make up an image on the screen.
2) Colour depth. The number of colours that can be displayed on the screen. The human eye can only distinguish between a few hundred shades of the same colour; the ability to display several thousand shades is of little practical importance.
3) Dot pitch. A method of gauging the quality of a monitor’s display that involves measuring the distance between the pixels on the screen. The smaller the distance between pixels, the finer the image will appear.
4) Refresh rate. A method of gauging the quality of a monitor’s display that involves measuring the number of times the image is drawn upon the screen each second.
Monitors are available in a rang of shapes and sizes. Portable computers tend to make use of liquid crystals displays (LCDs), similar to the much smaller displays found on pocked calculators. These monitors are often called TFT (thin film transistor) or active-matrix screens.
For TFT monitors, quality tends to be measured using several criteria:
-The dead pixels, -The response time, -The viewing angle
-The contrast ratio and the luminance (brightness).
Interlaced display- Each complete image shown on a monitor’s display is drawn in two steps.
Non-interlaced display- The monitor refreshes the display in a single pass.
PLOTTERS
A plotter uses a number of different coloured pens to draw lines upon the paper as it moves through the machine. Plotters are primarily used to create technical drawings, such as engineering diagrams.
OTHER OUTPUT DEVICES
-Sound. A sound card can be used to output information.
-MIDI devices. The ability to link devices to a personal computer via MIDI (musical instrument digital interface) connections allows users to send information directly to one or more musical instruments.
-Microfilm. Computer output to microfilm (COM), information is processed via a personal computer and sends directly to a device that produces microfilm
negatives.
SELECTING OUTPUT DEVICES
Some of the factors that should be considered when selecting an output device include appropriateness, permanence, speed, response time and cost.
PRINTERS
Laser printer-A laser is used to charge sections of a rotating drum which is then used to print using toner powder achieving a combination of speed with high print quality.
Inkjet printer-An inkjet printer uses a print-head containing 50 or more small nozzles that squirt ink onto paper by varying electrostatics charges produced by the printer.
Multi-function devices (MFDs)-A printer, often come with an automatic
SELECTING A PRINTER
A number of factors should be considered when selecting a printer:
Cost per page- Figures refers to the costs of consumables such as ink and replacement components (toner cartridges, drums and so on).
Dots per inch (dpi) - This describes the number of individual dots that can be printed within a space of one square inch.
Duty cycle- When referring to printers, this describes the typical monthly workload in terms of the number of pages printed.
Pages per month (ppm) - Manufactures often provide ratings for their printers that describe the typical workload appropriate for a given model.
Pages per minute (ppm) – A simple means of measuring the speed of a printer.
STORAGE DEVICES
Storage devices are used to store programs, data awaiting processing and the information resulting from computer processing. Storage devices are categorized as:
Primary storage- Data and instructions are loaded into memory such as random access memory. Such storage is temporary.
Secondary storage- Floppy disks and hard disks are secondary storage which provides permanent storage.
A brief description of several storage-device concepts:
Read-only- A device that can only be used to access data that are already present on the media and is unable to write data.
UNITS OF DATA MEASUREMENT
Bit- A single binary digit representing a 0 (zero) or a 1.
Byte- Made up of eight bits and represents the amount of space required to hold a single character.
Kilobyte (kb) - Approximately 1000 bytes, or the equivalent of 1000 characters.
Megabyte (Mb) - Approximately 1000 kb, or the equivalent of one million characters.
