Wednesday, January 28, 2009

Random Access Memory

Random Access Memory( RAM )
-Is a form of computer data storage.
-Today it takes the form of
integrated circuits that allow the stored data to be accessed in any order.
-The word random thus refers to the fact that any piece of data can be returned in a
constant time, regardless of its physical location and whether or not it is related to the previous piece of data.

-The word RAM is mostly associated with
volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off.

-Modern types of writable RAM generally store a
bit of data in either the state of a flip-flop, as in SRAM (static RAM), or as a charge in a capacitor (or transistor gate), as in DRAM (dynamic RAM), EPROM, EEPROM and Flash.

5 types of Ram
~ SRAM (Static Ram)
~DRAM (Dynamic Ram)
~SDRAM (Synchronous Ram)
~DDR RAM (Double Data Rate SDRAM)
~
SGRAM (Synchronous Graphics RAM)

# SRAM

Static random access memory (SRAM) is a type of
semiconductor memory where the word static indicates that, unlike dynamic RAM (DRAM), it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit.

SRAM exhibits
data remanence,[1] but is still volatile in the conventional sense that data is eventually lost when the memory is not powered.


# Dynamic random access memory
Dynamic random access memory (DRAM) is a type of
random access memory that stores each bit of data in a separate capacitor within an integrated circuit.
Since real capacitors leak charge, the information eventually fades unless the capacitor charge is
refreshed periodically.

Because of this refresh requirement, it is a dynamic memory as opposed to
SRAM and other static memory.








~SDRAM
SDRAM refers to synchronous
dynamic random access memory, a term that is used to describe dynamic random access memory that has a synchronous interface.

Traditionally, dynamic random access memory (
DRAM) has an asynchronous interface which means that it responds as quickly as possible to changes in control inputs.

SDRAM has a synchronous interface, meaning that it waits for a
clock signal before responding to control inputs and is therefore synchronized with the computer's system bus.

The clock is used to drive an internal
finite state machine that pipelines incoming instructions.




~DDR SDRAM
DDR SDRAM (double data rate synchronous dynamic random access memory) is a class of memory
integrated circuits used in computers.

It achieves nearly twice the
bandwidth of the preceding [single data rate] SDRAM by double pumping (transferring data on the rising and falling edges of the clock signal) without increasing the clock frequency.




Synchronous Graphics RAM (SGRAM)
SGRAM is a specialized form of SDRAM for graphics adaptors. It adds functions such as bit masking (writing to a specified bit plane without affecting the others) and block write (filling a block of memory with a single colour).
Unlike VRAM and WRAM, SGRAM is single-ported. However, it can open two memory pages at once, which simulates the dual-port nature of other video RAM technologies.


Sunday, January 18, 2009

Application software

Free ware
. Freeware is computer software that is available for use with no cost or for an optional fee.
Freeware is often made available in a binary-only, proprietary form, thus making it distinct from free software.
Freeware allows authors to contribute something for the benefit of the community, while at the same time allowing them to retain control of the source code, future direction of development and preserve its business potential.
Freeware is different from shareware, where the user is obliged to pay (e.g. after some trial period or for additional functionality).


Example:
.can get at down load.com
Trial version


Share ware
. The term shareware, popularized by
Bob Wallace, refers to copyrighted commercial software that is distributed without payment on a trial basis and is limited by any combination of functionality, availability, or convenience.
Shareware is often offered as a
download from an Internet website or as a compact disc included with a periodical such as a newspaper or magazine.

Packaged software
Ready-made application software.
In the early days of computing, any software that manufacturers didn't provide as part of the computer had to be custom-built to order.
In the 1980s, a new class of independent software vendors started to pre-build integrated software designed to fulfil a whole range of business functions, and these offerings became known as packaged software.
The term today typically refers to upscale enterprise software suites, such as ERP or CRM, rather than the shrinkwrap packages sold through retail outlets.
Packaged software, although ready-made, rarely comes ready-to-run.
It typically requires weeks or months of configuration work to set it up for the specific needs of each individual business.
This was an improvement on the previous generation of custom-built software, but today it is seen as inflexible, and an obstacle to integration between multiple applications.


Custom software
Custom software (also known as Bespoke software) is a type of
software that is developed either for a specific organization or function that differs from or is opposite of other already available software (also called off-the-shelf or COTSsoftware).
It is generally not targeted to the
mass market, but usually created for companies, business entities, and organizations.
Custom software is also when companies or governments pay for customized software for budget or project managing.
Examples of bespoke software include commercial products such as commercial websites, business databases and software for governments.
Non-commercial custom software development is common in academic and
open source circles.
Complex custom software can be developed on an increasingly small scale through the rise of rapid application development frameworks.
This means that smaller companies, charities or even individuals are able to benefit from complex software based on pre-built building blocks which are then customised to suit.


Public domain software
Refers to any
program that is not copyrighted.
Public-domain software is free and can be used without restrictions.
The term public-domain software is often used incorrectly to include
freeware, free software that is nevertheless copyrighted.

Programs that are uncopyrighted because their authors intended to share them with everyone else are in the public domain.
The UNIX community has developed a number of such programs over the years.
Programs in the public domain can be used without restriction as components of other programs.
When reusing such code, it is good to understand its history so that you can be sure it really is in the public domain.
Also see
shareware , which is programming that is "free" but more or less on a trial basis, and freeware .





Tuesday, January 6, 2009

drjay

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What is ASCII…????

-ASCII stands for American Standard Code for Information Interchange.
-Computers can only understand numbers, so an ASCII code is the numerical representation of a character such as 'a' or '@' or an action of some sort.
-ASCII was developed a long time ago and now the non-printing characters are rarely used for their original purpose.
-ASCII was actually designed for use with teletypes and so the descriptions are somewhat obscure.
-If someone says they want your CV however in ASCII format, all this means is they want 'plain' text with no formatting such as tabs, bold or underscoring - the raw format that any computer can understand.
- This is usually so they can easily import the file into their own applications without issues.

What is Unicode….???
-Unicode provides a unique number for every character, no matter what the platform,
no matter what the program, no matter what the language.
-The Unicode Standard has been adopted by such industry leaders as Apple, HP, IBM, JustSystems, Microsoft, Oracle, SAP, Sun, Sybase, Unisys and many others.
-The emergence of the Unicode Standard, and the availability of tools supporting it, are among the most significant recent global software technology trends.

Different between ascii and Unicode:

ASCII
~ follow the basic understanding of a computer.
~ASCII were only designed to support the very restricted typographic style available to typewriter users. The two ASCII characters
0x22 QUOTATION MARK

0x27 APOSTROPHE

are supposed to represent the neutral (vertical) glyphs commonly used on typewriters. They should not be used as directional quotation marks.


Unicode
~ provides a unique number for every character, no matter what the platform.
~ Unicode fonts are supposed to show the two accent characters

0x60 GRAVE ACCENT
0xB4 ACUTE ACCENT


as mutually symmetric shapes.



Below the cart of ASCII code...
" PLESE CLICK ON THE BOX BELOW "


Below the cart of Unicode....