Raster Systems And Resolution Buffers Computer Science Essay


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Consider three different raster systems with resolutions of 640 by 400, 1280 by 1024 and 2560 by 2048. What size frame buffer (in byte) is needed for each of these systems to store 12 bits per pixel? How much storage is required for each system if 24 bits per pixel are to be stored?

a): Frame Buffer size with 12 bits per pixel

For 640 x 400

Size = (640*480*12)/8 = 460800 bytes

For 1280 x 1024

Size = (1280 * 1024 * 12)/8 = 1966080 bytes

For 2560 x 2048

Size = (2560*2048*12)/8 = 7864320 bytes

b): Storage required for each system

For 640 x 400

Size = (640*480*24)/8 = 921600 bytes

For 1280 x 1024

Size = (1280 * 1024 * 24)/8 = 3932160 bytes

For 2560 x 2048

Size = (2560*2048*24)/8 = 15728640 bytes

Question 2.5:

Suppose an RGB raster system is to be designed using an 8-inch by 10-inch screen with a resolution of 100 pixels per inch in each direction. If we want to store 6 bits per pixel in the frame buffer, how much storage (in bytes) do we need for the frame buffer?


Screen Resolution = (8*10)*100=800*1000 pixels

Storage will be = (800*1000*6)/8 = 600000 bytes

Question 2.6:

How long would it take to load a 640 by 480 frame buffer with 12 bits per pixel, if 10^5 bits can be transferred per second? How long would it take to load a 24-bit per pixel frame buffer with a resolution of 1280 by 1024 using this same transfer rate?


a): Time to load 640 x 480 frame buffer

Time = (640*480*12) bits / 100000 bits/second = 36.864 seconds

b): Time to load 1280 x 1024 frame buffer

Time = (1280*1024*24) bits / 100000 bits/second =314.5728 seconds

Question 2.8:

Consider two raster systems with resolutions of 640 by 480 and 1280 by 1024. How many pixels could be accessed per second in each of these systems by a display controller that refreshes the screen at a rate of 60 frames per second? What is the access time per pixel in each system?


a): Pixels access through 640 x 480 resolution:

Pixels / second = (640*480 pixels)*60 frame/second =18432000 pixels / second

Time to access each pixel is 1/18432000 =0.00000005 seconds

b): Pixels access through 1280 by 1024 resolution:

Pixels / second = (1280 * 1024 pixels) * 60 frame/second = 78643200 pixels / second

Time to access each pixel is 1 / 78643200 = 0.00000001 seconds

Question 2.10:

How much time is spent scanning across each row of pixels during, screen refresh on a raster system with a resolution of 1280 by 1024 refresh rate of 60 frames per second?


Time / Row = 1 / (60 * 1280) = 0.00001302 seconds

Section B:

Research Report on Tablet Computer:


A "tablet computer” is a complete computer contained entirely in a flat touch screen that uses a stylus, digital pen, or finger tip as the primary input device instead of a keyboard or mouse which may or may not be included.

Unlike laptops, tablet personal computers may not be equipped with a keyboard, in which case they use a virtual onscreen substitute. All tablet personal computers have a wireless adapter for Internet and local network connection. Software applications for tablet PCs include office suites , web browsers, games and a variety of applications. However, since portable computer hardware components are low powered, demanding PC applications may not provide an ideal experience to the user.

The Tablet computer market was invigorated by Apple through the introduction of the iPad device in 2010. While the iPad places restrictions on the owner to install software thus deviating it from the PC tradition, its uncompromising attention to the touch interface, and its use of a "finger driven" multi-touch capacitive touch screen instead of a Stylus driven (for the higher precision needed to operate a tablet PC) is considered a milestone to the Tablet computer development history.

Developing programs for a tablet computer:

A significant characteristic to define whether a tablet computer can be regarded as a personal computer is the ability for the final user to install arbitrary or self-developed software. The new class of devices heralded by the iPad has spurred the tendency of a walled garden approach where the vendor reserves rights as to what can be installed. The software development kits for these platforms are restricted and the vendor must approve the final application for distribution to users. Proponents of open source software deem that these restrictions on software installation and lack of administrator rights makes this category one that cannot be properly named personal computers.

Tablets PC's vs. traditional notebooks:

The advantages and disadvantages of tablet PCs are highly subjective measures. What appeals to one user may be exactly what disappoints another. The following are commonly cited opinions of the tablet PC platform:


Usage in environments not conducive to a keyboard and mouse such as lying in bed, standing, or handling with a single hand.

Lighter weight, lower power models can function similarly to dedicated reading devices .

Touch environment makes navigation easier than conventional use of keyboard and mouse or touch pad in certain contexts such as image manipulation, or mouse oriented games.

Digital painting and image editing is enhanced and more realistic than painting or sketching with a mouse.

The ability for easier or faster entering of diagrams, mathematical notations, and symbols.

Allows, with the proper software, universal input, independent from different keyboard localizations.

Some users find it more natural and fun to use a stylus to click on objects rather than a mouse or touchpad, which are not directly connected to the pointer on screen.


Higher cost â€" convertible tablet PCs can cost significantly more than their non-tablet counterparts although this premium has been predicted to fall.

Input speed â€" handwriting can be significantly slower than typing speeds, the latter of which can be as high as 50-150 WPM; however, Slideit, Swype and other technologies are able to provide alternate, speedier methods of input.

Screen and hinge damage risk - Tablet PCs are handled more than conventional laptops, yet are built on similar frames; in addition, since their screens also serve as input devices, they run a higher risk of screen damage from impacts and misuse. A convertible tablet PC's screen hinge is often required to rotate around two axes, unlike a normal laptop screen, subsequently increasing the number of possible mechanical and electrical (digitizer and video cables, embedded WiFi antennas, etc.) failure points.

Ergonomics - a tablet PC does not provide room for a wrist rest while the screen is folded into slate mode. In addition, the user will need to move their arm constantly while writing.

Weaker video capabilities - Most tablet PCs are equipped with embedded graphics processors instead of discrete graphics cards. In July 2010, the only tablet PC with a discrete graphics card was the HP TouchSmart tm2t, which has the ATI Mobility Radeon HD5450 as an optional extra.

Hardware features:

Natural user interface

A tablet presents a more natural user interface to the user than a CLI or the traditional mouse driven WIMP interface (that is, a command line interface or a "Window, Icon, Menu, Pointing device" interface). The event processing of the operating system must respond to touches rather than clicks of a keyboard or mouse, which allows integrated hand-eye operation, a natural part of the somatosensory system. Although the device implementation differs from more traditional PCs or laptops, tablets are disrupting the current vendor sales by weakening traditional laptop PC sales in favor of the current tablet computers.

Touch technology

A key and common component among tablet computers is touch input. This allows the user to navigate easily and intuitively and type with a virtual keyboard on the screen. Touchscreens are usually one of two forms;

Resistive: Resistive touchscreens are passive and can respond to any kind of pressure on the screen. They allow a high level of precision (which may be needed, when the touch screen tries to emulate a mouse for precision pointing, which in Tablet personal computers is common) but may require calibration to be accurate. Because of the high resolution of detection, a stylus is often used for resistive screens. Although some possibilities exist for implementing multi-touch on a resistive touch-screen, the possibilities are quite limited. As modern tablet computers tend to heavily lean on the use of multi-touch, this technology has faded out and has been replaced by:

Capacitive: Capacitive touchscreens tend to have better accuracy and responsive than resistive screens. Because they require a conductive material, such as a finger tip, for input, they are not common among (stylus using) Tablet PCs but are more prominent on the smaller scale "tablet computer" devices for ease of use, which generally don't use a stylus, and need multi-touch capabilities.

Other touch technology used in tablets includes:

Palm recognition. It prevents inadvertent palms or other contacts from disrupting the pen's input.

Multi-touch capabilities, which can recognize multiple simultaneous finger touches, allowing for enhanced manipulation of on-screen objects.


Two major computer architectures compete in the tablet market, x86 and ARM architecture. X86, including x86-64, is popular on tablet PCs due to its use on laptops which can share common software and hardware. There are also non-PC based x86 tablets like the JooJoo. ARM gained popularity following the success of the iPad. ARM is more power and cost efficient for mobile computing and is gaining popularity for smaller tablets from other manufacturers such as Samsung with the Galaxy Tab which runs on Android.

Operating systems:

Tablets, like regular computers, can run a number of operating systems. These come in two classes, namely desktop-based operating systems and mobile-based ("phone-like") operating systems.

For the former class popular OS's are Microsoft Windows, and a range of Linux distributions. HP is developing enterprise-level tablets under Windows and consumer-oriented tablets under webOS. In the latter class the popular variants include Apple iOS, and Google Android. Manufacturers are also testing the market for products with Windows CE, Chrome OS, and so forth.

Research in Motion:

The BlackBerry PlayBook is a tablet computer announced in September 2010 which runs the BlackBerry Tablet OS. The OS is based on the QNX system that Research in Motion acquired in early 2010. Delivery to developers and enterprise customers is expected in October 2010.


Google's Linux-based Android operating system has been targeted by manufacturers for the tablet space following its success on smart phones due to its open nature and support for low-cost ARM systems much like Apple's iOS. In 2010, there have been numerous announcements of such tablets. However, much of Android's tablet initiative comes from manufacturers as Google primarily focuses its development on smart phones and restricts the App Market from non-phone devices. There is, moreover, talk of tablet support from Google coming to its web-centric Chrome OS. Some vendors such as Motorola are delaying deployment of their tablet computers until 2011, after Android is reworked to include more tablet features


HP's webOS: Following the acquisition of Palm by HP there has been long standing rumors of the cancellation of the HP Slate in favor of one running webOS.


The OLPC organization is developing a new version of the OLPC, strongly resembling a tablet computer, called the OLPC XO-3, running its "Sugar" operating system, based on Linux.

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