 A touch screen is an electronic visual display that any user can control and operate through simple or multi-touch gestures by touching the screen with a light pen or using fingers.  Touch screens enables users to interact with what is displayed, rather than using a mouse, touchpad, or any other intermediate devices. Touch screen technology has revolutionized smart phones and tablets, and is now finding its way into laptops, desktop displays, and all-in-one PCs.

 A few decades ago, touch screen could only be found in science fiction books and film. But now touch screens are in almost everywhere, in our homes, restaurants, stores, planes etc. It took generations and several major technological advancement for touch screens to achieve this kind of presence.  Although the underlying technology behind touch screens can be traced back to the 1940s, there are evidence that suggests that touch screens were not feasible until 1965.

 E.A Johnson is believed to be the first to develop the touch screen in but the tablet which was patented in 1969 could only read one touch at a time. After him, two engineers, Bent Stumpe and Frank Beck, developed a transparent, capacitive touch screen in the early  Samuel G Hurst founded the resistive touch screen in In 1990, a computer scientist Andrew scars conducted an academic study on human computer interactions.  Over the next few decades, touch screen technology continued innovating itself. Screens became more receptive to touch and gestures and more innovative moments were focused on the device.

 Touch screen have been used in many different devices over the years including ATM machines, cash registers in stores, computers POS (Point-of- Sale), consumer electronics, tablet PC etc.  Touch screen technology has the potential to replace most functions of the mouse and keyboard. The touch screen interface is being used in a wide variety of applications to improve human computer interaction. As the technology advances, people may be able to operate computers without mice and keyboards.

 Touch screens are based aroud four basic screen technologies- resistive; capacitive; surface acoustical wave and infrared.  RESISTIVE: Resistive LCD touch screen monitors rely on touch overlay, which is composed of a flexible top layer and a rigid bottom layer separated by insulating dots, attached to a touch screen controller.  Resistive touch screen panels are generally more affordable but offer only 75% clarity and the layer can be damaged by sharp objects. Resistive touch screen panels are not affected by outside elements such as dust or water.

 A capacitive touch screen panel is coated with a material that stores electrical charges. When the panel is touched, a small amount of charge is drawn to the point of contact. Capacitive touch screen panels must be touched with a finger unlike resistive and surface wave panels that can use fingers and stylus.  Capacitive touch screens have excellent clarity, and there are no moving parts to wear out. Liquids, dirt, grease, or other contaminants do not affect them. Unfortunately, gloved fingers will not activate the system.

 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.  A major benefit of such a system is that it can detect essentially any input including a finger, gloved finger, stylus or pen.  Unlike capacitive touch screens, infrared touch screens do not require any patterning on the glass which increases durability and optical clarity of the overall system.

 The Surface Acoustic Wave (SAW) technology is one of the most advanced touch screen types. Compared to Resistive and Capacitive technologies, SAW technology provides superior image clarity, resolution, and higher light transmission.  Disadvantages of Surface Acoustic Wave (SAW) technology include the facts that the touch screen must be touched by finger, gloved hand, or soft tip stylus (something hard like a pen won't work) and that the touch screen is not completely sealable.

1. Touching a visual display of choices requires little thinking and is a form of direct manipulation that is easy to learn. 2. Touch screens are the fastest pointing devices. 3. Touch screens have easier hand eye coordination than mice or keyboards. 4. No extra work space is required as with other pointing devices 5. Touch screens are durable in public access and in high volume usage.

1. User's hand may obscure the screen. 2. Screens need to be installed at a lower position and tilted to reduce arm fatigue. 3. Some reduction in image brightness may occur. 4. They cost more than alternative devices. 5. Screens get very dirty 6. These devices require massive computing power which leads to slow devices and low battery life