Tablet Computer
A Tablet PC is referred as combination of mobile and computer. It is larger than a smartphone or personal digital assistant, usually having touchscreen facilities. It often uses the on screen virtual keyboard or a digital pen. This is also known as Tablet PC, Tablet Computer, Mobile Computer, and Microsoft Tablet PC.The average size of a general Tablet is 10 inches but other tablet may be larger or smaller.
- Electronic tablet was the first patent device used for handwriting granted in 1888.
- The first patent for a system that recognized handwritten characters by analyzing the running handwriting was granted in 1915.
- The first publicly- demonstrated system using a tablet and handwriting text recognition instead of a keyboard for working with a modern digital computer in 1956.
Alan Curtis Kay (known as Alan Kay) attempted to formulate his Dynabook concept as a Tablet PC in 1968. That time his concept has not been fully realized.He sketches of the Dynabook show a device very similar to the tablet computers we have today, with a couple of exceptions. The Daybook had both a screen and a keyboard all on the same plane. The vision of Alan Kay was Touch Screen Technology at that time.
The Microsoft discovered own Tablet PC based on its own specification, and running a licensed its own WINDOWS OS in 2001.
How Tablet PC works:
The works of a Tablet PC is same as the works of a general PC works. The main difference is that a general PC doesn’t work on the touch screen. Now a day some LCD monitor manufacturing companies launches touch screen LCD in the market such as Apple, Samsung, Sony, and LG etc. As we know the brain of computer is CPU (Central processor Unit) as well as the brain of a Tablet PC is Microprocessor. This helps to save space and cut down heat generation. Heat is bad for all computers and all electronics devices. It tends to hardware failure that cause computer will not work properly till the alive hardware failure. It takes power from a rechargeable battery. An average battery life is eight to ten hours for a Tablet PC. Every Computer CPUs execute commands in clock cycles. The CPU runs in clock cycles per second, that more instructions it can process in milliseconds. Some tablets have underclocked processors, meaning the CPU is set to run fewer instructions per second than it's capable of executing. The reason for making a CPU underperform on purpose is to reduce heat production and conserve battery life.
Some typical component of a general Tablet PC is below:
- Accelerometers
- Gyroscopes
- Graphics Processor
- Flash based memory
- WI-Fi and Bluetooth
- USB port and Power Supply
- Speaker
- Touch screen controller chip
- Camera and chips
Accelerometers and gyroscopes help the tablet determine its graphical display orientation in either landscape or portrait mode.
The Graphics Processor Unit (GPU) takes the load off of the CPU when it comes to generating graphics.
The Wi-Fi component let us to connect network. Tablet PC also have a Bluetooth device that capable to receive and send data.
The USB port is used to transfer the data. And Power supply is used the recharge the rechargeable battery.
Speakeris used to listen music in loud sound.
How Touch Screen Works:
There are two ways to creating a Touch Screen for a Tablet PC and as well as Cell phone: resistive screens and capacitive screens. The both screen won’t work simultaneously. Resistive systems detect a touch on a screen through pressure. Tablets that require a stylus often use resistive screen.
Resistive screens:Resistive touch screens consist of a glass or acrylic panel that is coated with electrically conductive and resistive layers made with indium tin oxide (ITO) .The thin layers are separated by invisible spacers. Spacers hold the two layers apart.When the tablet is on, an electric current runs through both layers. If we put pressure on the screen, it causes the two layers to come into contact with one another. This changes the electrical field for those two layers. For example we want to access any application. We use our stylus to tap the application icon on our Tablet screen. The pressure from our touch causes the two layers in the resistive system to touch, changing the electric filed.A microchip inside the tablet interprets this change in the field and translates it into coordinates on the screen. The tablet's CPU takes these coordinates and maps them against its Operating System.The CPU determines that we have activated the app and launches it for us. Resistive screens are more sensitive to damage. If we use too much pressure, we may cause the resistive and conductive layers to be in constant contact. This will cause the tablet to wrong commands. Resistive screens also tend to have poorer resolution than capacitive screens.
Characteristics of Resistive screen:
- Cost effective solutions.
- Activated by a stylus, a finger or gloved hand.
- Not affected by dirt, dust, water, or light.
- 75%~85% clarify.
- Resistive layers can be damaged by a very sharp object.
Capacitive Screen: A capacitive touchscreen panel consists of an insulator such as glass,coated with a transparent conductor such as indium tin oxide (ITO).A human body is an electric conductor, so when we touch the screen with a finger, a slight amount of current is drawn, creating a voltage drop. When we touch a conductive material to this screen, some of that electrical charge transfers over to whatever is touching it. But the material must be conductive or the device won't register a touch. In others words we can use anything to touch a resistive screen to register a charge but only conductive material will work on a capacitive system.Capacitive systems tend to be more robust than resistive systems since you don't have to press down as hard to register a touch. They also tend to have a higher resolution than resistive systems.
Characteristics of Capacitive screen:
- Durable and resistant to scratches for demanding applications.
- Faster and more responsive than resistive screen.
- Immune to surface contaminants.
- Superior optical clarity, brighter display and less surface reflection.
- Must be touched by finger, will not work with any non-conductive input.
Most of the time, these systems are good at detecting the location of exactly one touch.If we try to touch the screen in several places at once, the results can be erratic. Some screens simply disregard all touches after the first one. Others can detect simultaneous touches, but their software can't calculate the location of each one accurately. There are several reasons for this, including the following:
- Many systems detect changes along an axis (x, y) or in a specific direction instead of at each point on the screen.
- Some screens rely on dimension of system to determine touch locations.
But this is not happen with an Apple iPhone.Many of the elements of its multi-touch user interface require us to touch multiple points on the screen simultaneously. For example in the Apple iPhone if we want to zoom in into a Web page or Images content by the help of placing our thumb and finger on the screen and spreading them apart. To zoom out, we can our thumb and finger together from screen then it comes in normal position. The iPhone's touch screen is able to respond to both touch points and their movements simultaneously.
Resistive screen:
Diagram of resistive screen