A touch screen is an electronic visual display that can detect the presence and location of a touch within the display area. Touch screens can sense
Finger and other passive objects, such as a stylus. However, if the object sensed is active, as with a light pen.

• In 1971 Dr. Sam Hurst, founder of Elographics developed the first touch opaque sensor “Elograph” at the University of
Kentucky.
• In 1974 He developed the first real touch screen.
• In 1977, Elographics developed the five-wire resistive technology then with the backing of Siemens Corporation, developed a curved glass sensor called the touch screen .
• The new transparent technology, AccuTouch, was later developed by the founders of Elographics, Dr. Hurst and Bill
Colwell

The father of the touch screen technology is Dr. Samuel Hurst. In 1971, while he was working as an instructor at the University of
Kentucky Research Foundation, he had to read a great volume of information during the graduation exams. In an effort to save some time he invented the first touch sensor that he called “Еlo graph”(electronic graphics), which allowed him to enter data faster.

Apple was the first with a touch screen phone in 1983. Jason
Ford of Elo Touch Systems, the company whose founder invented touch screen technology, for providing the touch technology. In 1971, the first "touch sensor" was developed by Doctor Sam
Hurst.

The Nokia 7710 is a first touch screen mobile phone model produced by Nokia. The 7710 is based on the Nokia 7700 which was never released. It is Nokia's first, and so far only smart phone to run the Series 90 GUI a top the Symbian OS.

There are mainly 4 types of touch Technologies:-
1.Resistive
2. Surface acoustic wave
3. Capacitive
4. Infrared

A resistive touch screen panel is composed of several layers, the most important of which are two thin, metallic, electrically conductive layers separated by a narrow gap. When an object, such as a finger, presses down on a point on the panel's outer surface the two metallic layers become connected at that point. This causes a change in the electrical current, which is registered as a touch event and sent to the controller for processing. It is used in Grocery Stores, Hotels, Restaurants and
Retail Stores.

•
Advantages
– Cost-effective solution
– Activated by any stylus
– Very accurate
– Low power requirements
– Liquids won't affect touch screen performance
• Disadvantages
– Polyester surface can be damaged
– Lower endurance (35 million touches)

Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touch screen panel.
When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. SAW touch screen technology is suggested for use in ATMs, Amusement Parks, Gaming
Environments, Industrial Control Rooms etc.

•
Advantages
– Durable glass construction
– High optical clarity
– Activated by a finger, gloved hand, or soft tip stylus
• Disadvantages
– Moving liquids or condensation can cause false touches
– Solid contaminants create non-touch areas until removed
– Doesn't support drag or draw effectively

A capacitive touch screen panel consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide (ITO). As the human body is also a conductor, touching the surface of the screen results in a distortion of the body's electrostatic field, measurable as a change in capacitance.

•
Advantages
– Scratch resistant, durable surface
– High endurance (225 million touches)
– Very accurate
– Good optical clarity
– Liquids won't affect touch screen performance
•
Disadvantages
– Does not work with gloved fingers or stylus

An infrared touch screen uses an array of X-Y infrared LED and photo detector pairs around the edges of the screen to detect a disruption in the pattern of LED beams.
Infra-red bezels have proven to be a very reliable technology for use in
ATMs,Medical Instrumentation and Transportation Tracking applications.

•
Advantages
-Highest quality of underlying image
-Very high transmittance
-Excellent anti-glare, with use of chemically etched glass
-Can be activated with almost any device
-Higher accuracy than other technologies
-Very high durability and reliability
•
Disadvantages
- Surface obstructions can cause a false touch
–
It is very sensitive and can be activated by stray touches.
–
Low resolution
–
Parallax problems

Resistive Infrared SAW Capacitive
Touch
Resolution
Clarity
High
Average
High
Good
Average
Good
High
Good
Operation
Durability
Finger or Stylus Finger or Stylus Finger or Softtipped Stylus
Finger only
Can be
Damaged by
Sharp Objects
Highly Durable Susceptible to
Dirt and
Moisture
Highly durable

Touch screens have several advantages over other pointing devices:
• A touch screen is easy to use (as the user simply touches what he or she sees on the display).
• Save space as no buttons are required.
• Touching a visual display of choices requires little thinking and is a form of direct manipulation that is easy to learn.
• Touch screens are the fastest pointing devices.
• Touch screens have easier hand eye coordination than buttons.
• Touch screens are durable in public access and in high volume usage.

• Screen has to be really big not to miss things when pressing them with your finger:
• Big screen leads to low battery life.
• Touch screen means screen can’t be read too well in direct sunlight as it applies an additional not 100% transparent.
• Touch screen devices usually has no additional keys (see the iPhone) and this means when an app crashes, without crashing the OS, you can’t get to the main menu as the whole screen becomes unresponsive.
• Most user interfaces are not optimized for thumb operation, so a stylus in necessary, and this means using two hands
• Screens get very dirty.
• These devices require massive computing power which leads to slow devices.

Though the touch screen technology contains some limitations it’s very user friendly, fast, accurate, easy for the novices & fun to operate. It has been widely accepted. And now by just modifying a little it can replace the mouse and key board completely in near future.