Computers

Java has many more than 3 characteristics, which can be labelled "advantages"; of course, most of the following are shared by several other languages.

• Java is object oriented (I wouldn't want to program on any language that doesn't!)
  
• Java runs on multiple platforms (Windows, Linux, etc. - some languages work only for Windows, for example).
  
• Java has native support for Unicode - this is the standard for strings. (This makes it easy to use Java with different languages, including languages that don't use the Latin alphabet.)
• Java has built-in support for multithreading. This makes it possible to run several things at once.
• The designers of Java have put a lot of effort into detecting many error situations during compilation. That will increase the quality (stability) of the finished product.
• Java is free.
• There is a huge collection of components already written in Java, for different aspects. This means that in many cases, you don't have to design everything from scratch.

In most cases, you will want to use abstract classes IN ADDITION to interfaces.

You should use an abstract class in the following circumstance:

1. the abstract class is clearly part of class hierarchy, and does not just describe some sort of basic functionality. Specifically, abstract classes are a good idea where they will be directly inherited from to create a concrete concept, but the abstract class itself is too indistinct to have any specific instance of it created.
2. You want to provide an implementation for a set of methods that will be reused by a significant number of other classes, all of which can be fit into a class hierarchy.

In practice, abstract classes are a good way to collect common code into one place, to make maintenance easier.

For instance, say you have a class and interface structure like this:

Class A

Interface X

Class B extends A implements X

Class C extends A implements X

Both B and C will have the all the methods declared in X; if the implementation of those methods is the same (or can be made the same), then X is a good candidate for changing to an abstract method:

Class A

Abstract Class X extends A

Class B extends X

Class C extends X

Thus, you have removed the code duplication that was happening when using interfaces.

Note that doing the above is NOT a good idea if any class which implement interface X cannot be made a subclass of the new abstract class X.

DDA Line Drawing Algorithm

Step 1:[Determine The Dx & Dy]

Dx=Xb-Xa

Dy=Yb-Ya

Step 2:[Determine Slope is Gentle or Sharp]

If |Dx|>|Dy| then

Gentle Slope

M=Dy/Dx

Set The Starting Point

If Dx>0 Then

C=CELING(Xb)

D=Yb+M*(C-Xb)

F=FLOOR(Xa)

R=FLOOR(D+0.5)

H=R-D+M

IF M>0 Then

Positive Gentle Slope

M1=M-1

Now Step Through The Columns

WHILE C<=F

According to Wikipedia,

"In computer science and computer programming, a data type or simply type is a classification identifying one of various types of data, such as real-valued, integer or Boolean, that determines the possible values for that type; the operations that can be done on values of that type; the meaning of the data; and the way values of that type can be stored."

"Almost all programming languages explicitly include the notion of data type, though different languages may use different terminology. Common data types may include:

• integers,
• booleans,
• characters,
• floating-point numbers,
• alphanumeric strings."

= What is information processing cycle? = In: Computer Terminology [Edit categories]

[Edit]

Information processing cycle of computer can be well described by the following points: (1) input, (2) processing, (3) output and (4) storage # Input-entering data into the computer. # Processing-performing operations on the data. # Output-presenting the results. # Storage-saving data, programs, or output for future use.

1. INPUTThe collection of raw data from the outside world so it can be put into an information system. Putting the acquired data into the information system. # Examples: The payroll clerk collects workers' timecards so she knows how many hours each person worked that week and types the hours from the timecards into a spreadsheet # Conducting a survey of customer's opinions and then scanning the survey cards with a card reader. # Collecting jokes for a joke book and typing jokes into a word processor. # Using a form on a website to collect visitors' opinions

Typical input devices: Keyboards, mice, flatbed scanners, bar code readers, joysticks, digital data tablets (for graphic drawing), electronic cash registers

2. PROCESSING CPU Processor - Central ProcessingUnit A central processing unit (CPU), or sometimes simply processor, is the key component in a digital computer capable of executing a program. It interprets computer program instructions and processes data. CPUs provide the fundamental digital computer trait of programmability, and are one of the necessary components found in computers of any era, along with memory and input/output facilities. A CPU that is manufactured as a single integrated circuit is usually known as a microprocessor. Beginning in the mid-1970s, microprocessors of ever-increasing complexity and power gradually supplanted other designs, and today the term "CPU" is usually applied to some type of microprocessor. Microprocessor (CPU)

Integrated circuit, also called a chip. The Brain of the computer

Composed of: ALU: Arithmetic Logic Unit: Processor Controller High speed calculator

Intel is the most popular chip

Categorized by model numbers

Higher model number=newer/faster chip

Speed of CPU is determined by clock speed

Higher the clock speed, faster the computer

Speed is measured in megahertz (MHz) Megahertz: Clock Speed of the processor (100 MHz = 100 million cycles/second). Memory or RAM Next most critical element of a processing hardware is RAM, often referred to as "primary storage" or "main memory". Random Access Memory (RAM) receives and temporarily stores data and program instructions from the CPU This data bank communicates with the CPU, constantly exchanging information and constantly changing as long as the computer is on

RAM is an active, electronic state. When the power is on, RAM retains data. When the computer is turned off, all data in RAM is erased unless you have saved it to some mass storage device. Each time the computer boots, the computer goes through it's startup routine and lastly loads operating system instructions into RAM

Random Access Memory (RAM) is the workhorse behind the performance of your computer. Working as a foot soldier for your processor, RAM temporarily stores information from your operating system, applications, and data in current use. This gives your processor easy access to the critical information that makes your programs run. The amount of RAM you have determines how many programs can be executed at one time and how much data can be readily available to a program. It also determines how quickly your applications perform and how many applications you can easily toggle between at one time. Simply put, the more RAM you have, the more programs you can run smoothly and simultaneously. To determine how much RAM you need, factor in the demands of the applications you want to run simultaneously as well as the operating system (512 MB of RAM is recommended by Microsoft as minimum for operation of Windows) Then keep in mind that you'll inevitably add new applications and create new files, and add accordingly. RAM: (Random Access Memory): (Click here to read "How Stuff Works - RAM") Types of RAM * DRAM (Dynamic RAM) This is the most common type of computer memory. DRAM needs refreshing and is refreshed hundreds of times each second in order to retain data. During recharging it cannot be accessed by the CPS * SRAM (Static RAM) SRAM is approximately 5 times faster (and twice as expensive, as DRAM). It does not have to be constantly refreshed. Because of its lower cost and smaller size, DRAM is preferred for the main memory, while SRAM is used primarily for cache memory. * SDRAM (synchronous dynamic RAM) is the standard memory offering in the PC industry and is faster than DRAM because it's synchronized to the system clock. . It is designed for mainstream home and business applications, email, and basic audio and video streaming. It provides single-channel memory and is available on our mainstream and value desktop system. * DDR SDRAM (double data rate synchronous dynamic RAM) takes all the features of ordinary SDRAM and increases the frequency bandwidth to improve system performance and speed. * RDRAM (Rambus dynamic RAM) is able to load a new stream of data before the previous stream has completed, resulting in faster access speeds. The RDRAM memory features dual-channel processing which doubles data throughput to further enhance performance. This type of memory is optimized for high-end multimedia tasks involving video and audio. Dual Channel RDRAM is shipped on our performance desktop systems powered by Pentium 4 processors * VRAM: Memory designed for storing the image to be displayed. * CACHE RAM is a small block of high-speed memory located between the Processor and main memory and is used to store frequently requested data and instructions. When the processor requests data, it will check in the cache first

Understanding the relationship between CPU and RAM The hierarchical arrangement of memory storage in current computer architectures is called the memory hierarchy. It is designed to take advantage of memory locality in computer programs. Each level of the hierarchy is of higher speed and lower latency, and is of smaller size, than lower levels. The memory hierarchy in most computers is as follows: * Processor registers - fastest possible access (usually 1 CPU cycle), only hundreds of bytes in size * Level 1 (L1) cache - often accessed in just a few cycles, usually tens of kilobytes * Level 2 (L2) cache - higher latency than L1 by 2× to 10×, often 512 KiB or more * Level 3 (L3) cache - higher latency than L2, often several MB * Main memory (DRAM) - may take hundreds of cycles, but can be multiple gigabytes. Access times may not be uniform.

3. Output In information processing, output is the process of transmitting the processing information Essentially, output is the presentation of any data exiting a computer system. This could be in the form of printed paper, audio, video. In the medical industry this might include CT scans or x-rays. Typically in computing, data is entered through various forms (input) into a computer, the data is often manipulated, and then information is presented to a human (output). Typical output devices: Monitors* Pixels: Images are created with dots of lights called picture elements, or pixels. More pixels = higher resolution. Resolution is the maximum number of pixels the monitor can display * Basic VGA is a pixel grid 640 X 480 * Super VGA is 1,024 X 768 * A video card, (also referred to as a graphics accelerator card, display adapter, graphics card, and numerous other terms), is an item of personal computerhardware whose function is to generate and output images to a display. Printers * Laser - laser beams bond toner to paper * Ink jet - fine stream of ink * Dot Matrix - pins & ribbon What else can you think of?

4. Storage Storage, or mass storage refers to various techniques and devices for storing large amounts of data. The earliest storage devices were punched paper cards, which were used as early as 1804 to control silk-weaving looms. Modern mass storage devices include all types of disk drives and tape drives. Mass storage is distinct from memory, which refers to temporary storage areas within the computer. Unlike RAM memory, mass storage devices retain data even when the computer is turned off. The smallest unit of storage is a file that contains such data as a resume, letter, budget, images or any one of the thousands of items that you may have saved for future reference. Additionally, files can be executable program files, or system files reserved for the operating system. Mass storage is measured in kilobytes (1,024 bytes), megabytes (1,024 kilobytes), gigabytes (1,024 megabytes) and terabytes (1,024 gigabytes). Examples of some mass storage devices * Disk storage - hundreds of thousands of cycles latency, but very large ** Floppy Disks: Relatively slow and have a small capacity, but they are portable, inexpensive, and universal ** Hard disks : Very fast and with more capacity than floppy disks, but also more expensive. Some hard disk systems are portable (removable cartridges), but most are not. * Tertiary storage - ** Optical storage: Unlike floppy and hard disks, which use electromagnetism to encode data, optical disk systems use a laser to read and write data. Optical disks have very large storage capacity, but they are not as fast as hard disks. Examples: CD, CD-R, CD-RW, DVD or DVD-R ** Tapes: Relatively inexpensive and can have very large storage capacities, but they do not permit random access of data. * Flash Memory - faster than disk storage, with up to 4GB or more of data, transferring (usually) over universal serial bus (USB) POONAM VALERA GUJRAT JAMNAGAR p_aum_k@yahoo.co.in