Computer Memory

Memory is major part of computers that categories into several types. Memory is best storage part to the computer users to save information, programs and etc, The computer memory offer several kinds of storage media some of them can store data temporarily and some them can store permanently. Memory consists of instructions and the data saved into computer through Central Processing Unit (CPU).

The performance of computer mainly based on memory and CPU. Memory is internal storage media of computer that has several names such as majorly categorized into two types, Main memory and Secondary memory.

1. Primary Memory / Volatile Memory:

Primary Memory also called as volatile memory because the memory can’t store the data permanently. Primary memory select any part of memory when user want to save the data in memory but that may not be store permanently on that location. It also has another name i.e. RAM.

Random Access Memory (RAM):

The primary storage is referred to as random access memory (RAM) due to the random selection of memory locations. It performs both read and write operations on memory. If power failures happened in systems during memory access then you will lose your data permanently. So, RAM is volatile memory. RAM categorized into following types.

DRAM
SRAM
DRDRAM

2. Secondary Memory / Non Volatile Memory:

Secondary memory is external and permanent memory that is useful to store the external storage media such as floppy disk, magnetic disks, magnetic tapes and etc cache devices. Secondary memory deals with following types of components.

Read Only Memory (ROM) :

ROM is permanent memory location that offer huge types of standards to save data. But it work with read only operation. No data lose happen whenever power failure occur during the ROM memory work in computers.

ROM memory has several models such names are following.

1. PROM: Programmable Read Only Memory (PROM) maintains large storage media but can’t offer the erase features in ROM. This type of RO maintains PROM chips to write data once and read many. The programs or instructions designed in PROM can’t be erased by other programs.

2. EPROM : Erasable Programmable Read Only Memory designed for recover the problems of PROM and ROM. Users can delete the data of EPROM thorough pass on ultraviolet light and it erases chip is reprogrammed.

3. EEPROM: Electrically Erasable Programmable Read Only Memory similar to the EPROM but it uses electrical beam for erase the data of ROM.

Cache Memory: Mina memory less than the access time of CPU so, the performance will decrease through less access time. Speed mismatch will decrease through maintain cache memory. Main memory can store huge amount of data but the cache memory normally kept small and low expensive cost. All types of external media like Magnetic disks, Magnetic drives and etc store in cache memory to provide quick access tools to the users.

Overview of Computers

Two systems of computers:
1) PC – the Personal Computer              
2) Mac – the Apple Macintosh.

Two designs of computers:
1) desktop
2) laptop (notebook)

Computer architecture:  
Main components of a computer            Multimedia devices                  Other peripheral devices

1)  computer                                        1)  CD-ROM / DVD drive         1)  printer            
2)  monitor                                          2)  video card                              2)  scanner  
3)  hard disk/ hard drive                      3)  soundcard                              3) CD-recorder,CD-R/CD- RW  4)  keyboard                                        4)  speakers                                4)  modem      
5)  mouse / trackball /                         5)  headphones / headset             5)  USB flash drive                
    touch pad                                        6)  microphone                             6)  webcam            
                                                                                                                 7)  digital camera
                                                                                                                 8)  digital voice recorder
                                                                                                                 9)  camcorder
Inside the Computer

1) Processor:
The CPU (Central Processing Unit), a complete computation engine that is fabricated on a single chip, is the computer’s brain. It is sometimes referred to as the central processor, microprocessor, or just processor. Two typical components of a CPU are: 1) the arithmetic logic unit (ALU), which performs arithmetic and logical operations, and 2) the control unit, which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.

2) Memory:
ROM (Read Only Memory) is the computer’s permanent, long-term memory. Tere are types of ROM called PROM that can be altered. The P stands for programmable. ROM's purpose is to store the basic input/output system (BIOS) that controls the start-up, or boot process.
RAM (Random Access Memory) is a working area where the operating system (e.g. Windows), programs and data in current use are kept, ready to be accessed by the processor. It is the best known form of computer memory. However, RAM, unlike ROM, is emptied when the computer is switched off. The more RAM you have, the quicker and more powerful your computer is.
There are two basic types of RAM: dynamic RAM (DRAM) and static RAM (SRAM).
The two types differ in the technology they use to hold data. DRAM, the more common type, needs to be refreshed thousands of times per second. SRAM does not need to be refreshed, which makes it faster, but it is also more expensive than DRAM.

Memory is measure in the following units:
-  1 byte = 8 bits (Each 1 or 0 is called a bit (i.e. binary digit). Each character (i.e. a letter, a number, a space, or a punctuation mark) has its own arrangements of 8 bits, e.g. 01000001 = “A”, 01000010 = “B”.
-  1 KB (kilobyte) = 1024 (210) bytes
-  1 MB (megabyte) = 1024 (210) KB
-  1 GB (gigabyte) = 1024 (210) MB
     
Cache (pronounced as "cash") is a buffer (made of a small number of very fast memory chips) between main memory and the processor. It temporarily stores recently accessed or frequently-used data. Whenever the processor needs to read data, it looks in this cache area first. If it finds the data in the cache, then the processor does not need to do more time-consuming reading of data from the main memory. Memory caching allows data to be accessed more quickly.

Storage Devices
The most common forms of storage devices in a home computer are:
- Hard disk drive
- Floppy disk
- CD-ROM
- CD-R and CD-RW
- DVD-ROM
- USB flash drives

Monitor
There are two types of monitors available for PCs: the traditional CRT (cathode ray tube) and the newer LCD (liquid crystal display). The CRT is used for both televisions and computers. It produces a good quality image at a number of different settings for a reasonable price. LCD monitors, also known as flat panel displays, are used in laptop (or notebook) computers and more frequently for desktops as well. They are lighter and smaller (only inches thick) than CRTs with reduced electromagnetic emissions and power consumption.

Video Card
The card here is a jargon for an electronic circuit board. Video cards are also known as graphics cards, which are responsible for displaying 2D and 3D images on your monitor. 2D graphics are the regular pictures and images that appear on your screen while 3D graphics are mostly used in games and imaging.

Sound Card
A sound card is an electronic circuit board that is mounted inside the computer to control sound output to speakers or headphones, to record sound input from a microphone connected to the computer, and to manipulate sound stored on a disk. Sound cards are essential for multimedia applications and have become common on modern personal computers.
Many sound cards are also Windows-compatible. Many multimedia applications require the system to have a Windows-compatible sound card to run properly.

Ports
A port is an interface on a computer to which you can connect a device. Personal computers have various types of ports. Internally, there are several ports for connecting disk drives, monitors, and keyboards. Externally, personal computers have ports for connecting modems, printers, mice, and other peripheral devices.

There are three common types of external ports that usually come with a computer:

1) Parallel ports (for most printers)
2) Serial ports (for most modems and some mice)
3) USB (Universal Serial Bus) ports (for about every peripheral made in a USB version)

List of Open Source computer software programs

Some of the most useful computer software are given below for everyone to understand and download:

Firefox web browser: Browse the web with this awesome web browser. It's not only open source but also a product of Non Profit Organization(Mozilla Corporation).

Mozilla Thunderbird: Read and send email directly from your desktop.

RSSOwl Newsreader: Get latest news directly without searching or browsing websites.

VLC media player: Play your favorite music or videos.

GIMP: Edit or create photos, it offers many great features.

OpenOffice: Create and edit documents, presentations, spreadsheets and many more. It is compatible with file formats used by Microsoft Office.

Miro Video Converter: Convert videos to many different formats including Android, iPhone.

Miro: Awesome music and video player, allows you to search videos directly from it, browse websites, download torrents, listen to podcast.

PeaZip: Create and extract archived files.

Notepad++ text editor: A very useful text editor that allows files to be opened in tabs, advanced search and replace, auto completion and you can customize it by downloading additional plugins.

Ubuntu Operating System: Linux distribution which is easy to use, configure and learn. If you wish to switch to Linux then it's simple with Ubuntu.

Slow Up by George Saoulidis. $8.99 from Smashwords.com
How Fast Can You Think? Limitless meets Black Mirror in this novel that pushes the limits of a couple's minds.

Play games

There are many free games that you can download and play. Some of them which i like are:
Supertuxkart: Solve challenges and compete with others.

Computer Function Diagram

Computer Parts Diagram - easy to understand for children

Third-Generation Computers (1964 - 1971)

In the third generation of computers integrated circuits (ICs) began to be used. These ICs were called chips. An IC is more compact than a transistor. A single IC has many transistors, registers and capacitors, placed on a single thin slice of silicon. So, the computer built of such components become smaller. Some of the computers developed during this period were :

IBM-360: Developed by IBM in 1964

PDP-8: Developed by DEC in 1965

PDP-11: Developed by DEC in 1970

CRAY-1: Developed by Cray Research in 1974

VAX: Developed by DEC in 1978.

High-Level languages such as BASIC (Beginners All-purpose Symbolic Instruction Code) were developed during this period.

The advantages that the third-generation computers had over the second-generation computers were:

1. They were smaller in size as compared to the second-generation computers.

2. They generated less heat.

3. They reduced computational time.

4. They involved low maintenance cost.

5. They were easily portable.

6. They required less power to keep them going.

7. They were comparatively cheaper.

Second-Generation Computers

In this generation of computers, transistors were used in place of vacuum tubes. Transistors are more compact than vacuum tubes as they are made up of semiconductors. they are also more durable than vacuum tubes. Programming languages such as COBOL and FORTRAN were developed during this period. Some of the computers of the second generation are:

IBM 1620: Its size was smaller as compared to the first-generation computers and it was used mostly for scientific purposed.

IBM 1401: It was used for business applications

CDC 3600 : It was used for scientific purposes.

The advantages that the second-generation computers had over the first-generation computers are:

1. They were smaller as compared to the first-generation computers

2. They generated less heat.

3. They took comparatively less computational time.

4. They were less prone to failure.

The disadvantages that second-generation computers had as compared to the first-generation computers are:

1. They required air conditioning

2. Frequent maintenance was required.

3. They were difficult to produce and were quite expensive.

Characteristics of Computers

Useful characteristics of computers
1. Speed :
The computer present in the modern world has the speed of nano and pico second. The various speed that are used by the computers from the former generations are as follows:

1 milli second=1*10^-3 second
1 micro second=1*10^-6 second
1 nano second=1*10^-9 second
1 pico second=1*10^-12 second
2. Accuracy: The accuracy of computers is quite high. They are reliable and robust. It ever makes a mistake. Most probably the error occurs due to the user rather than the computer. There may be certain hardware mistake but with the advanced technique in hand they are overcome.
Example:Only accurate robots are used to perform the operations for the patients since human hands are not flexible for making operations.

3. Diligence: Unlike human beings, computers are persistent and are not afflicted by tiredness, monotony, lack of concentration, etc.
If there are surplus amount of executions to be made then each and every execution will be executed at the same time period. They can perform their assigned task without taking any refreshment.

Example: Computers which are used for controlling the satellites.
4. Reliability: Computers produce reliable and precise results. Humans cannot work with such precision. The computers are automatic. It may execute the process without any intervention of user once they are assigned to a work. Once the data or instruction are fetched from the secondary devices such as optical disks, hard disks etc. Immediately they get stored into RAM (primary memory) and then sequentially they get executed.

5. Versatility: Computers can work with different types of data like sound, graphics, audio, etc. In our day to day life computers has been a part, with their extended flexibility they are used, all over the world. They can be used as personal computers, for home uses, for business oriented tasks, weather forecasting, space explorations, teaching, railways, banking, medicine etc. All Modern computer can perform different kind of tasks simultaneously.

6. Memory: Computers can store large amounts of data for years till a hardware failure occurs.
Secondary storage devices are the key for the data storage. They store the data for which the user wants to retrieve these data for future use. The examples for various secondary devices are Floppy disk, Optical disks (CS and DVD), Zip drives, Thumb drives etc. The data of smaller size can be easily fetched and they can be copied to the primary memory (RAM).

Example: Data Warehousing made by IBM.

Computers today have the following limitations:
1. No IQ : Computers possess no intelligence of their own. They do what they are instructed to do. They do not have brains and hence cannot think.
2. No feelings: Since computers cannot think, they also do not have any feeling.

The Evolution of Computers

Computers have evolved through different stages before reaching their present state of development. The history of the computer dates back to 3000 BC. Different stages of its development are as follows:

3000 BC - Invention of the Abacus
AD 1500 - Mechanical calculator invented by Leonardo da Vinci
AD 1621 - Slide rule invented.
AD 1640 - Blaise Pascal invents the Arithmetic Machine
AD 1800 - Jacquard invents the first punch cards for storing data
AD 1822 - Charles Babbage invents the Difference Engine
AD 1830 - Charles Babbage invents the analytical Engine
AD 1857 - Sir Charles Wheatstone uses paper tape to store data
AD 1926 - The first patent for semiconductor transistor was filed.
AD 1936 - Dvorak keyboard created.
AD 1937 - Alan Turing defines the Turing Test.
AD 1940 - Konrad Zuse completes the first fully-functioning electro-mechanical computer of the world.
AD 1943 - The first electronic general-purpose computer, ENIAC, produced.

Types of Computers

Depending upon the way a system performs, a computer can be classified into the following types:

1. Digital

2. Analog

3. Hybrid

Digital Computers

It works with digits and numbers. For example, to calculate the distance travelled by a car, you might take into consideration the diameter of the tyre to calculate the circumference, the number of revolutions of the wheel per minute, the time taken in minutes, and then multiply them all to get the distance moved. This is known as digital calculation.

Digital computers can be classified on the basis of size and capabilities into :-

Super Computers

Mainframe Computers

Mini Computers

Micro computers

Personal Computes

Analog Computers

This computer  works on the principle of using continuous measurements of physical phenomenon like breath, rotation, electric effects, etc. Take the example of the principle of the milometer in a car. when the wheels of a car rotate, they make some gears to move. This movement is transmitted to the centre by a flexible shaft. The meter itself contains some gears/wheels marked with numerical numbers and is calibrated to calculate the exact distance travelled in metres or kilometres. In an analog computer, the input and output are continuously varying quantities such as voltage, instead of the discrete digits of digital computers.

Hybrid Computers

There are some computes which employ both digital as well as analog quantities. these are known as hybrid computers. For example, a digital thermometer employs a mechanism which converts the temperature observed into digital form using analog-to-digital conversion. Hybrid computers are the computers that are generally used in the process of control environment, where an analog (or continuously varying) input is provided to a computer which processes it digitally and presents the output in the analog or digital form as required.

Components of a Computer

The internal architechtural design of computers may differ from one another. But there is a basic organization seen in all computers
The block diagram of basic computer organization is shown below:

The diagram shows that a computer consists of the Central Processing Unit (CPU), memory and input / output unit.

Iterative Statement: do-while Loop

It is another repetitive control structure provided by C++. It is an exit control loop. It evaluates its test-expression after executing its loop body statements. A do-while loop always executes at least once.
The syntax of the do-while loop is
do
{
statement;
}
while ;

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Iterative Statement : While Loop

The while loop.
As mentioned earlier, the while loop is an entry controlled loop. The syntax of a while loop is
while (condition) statement
and its function is simply to repeat statement while expression is true. While is a reserved word of C++; condition is a Boolean expression; and statement can be simple or compound statement.
For example, we are going to make a program to count down using a while loop: LEARN MORE>>

Iterative Statement : for Loop

For some programming objectives it is necessay to repeat a set of statements a number of times until a certain condition is fulfilled. In such situations iteration statements can be used. The iteration statements are also called loops or looping statements.
Parts of a loop
1. Initialization Expression.
2. Test Expression
3. Update Expressions
4. Body of the loop.
The for Loop
The for loop is a deterministic loop in the sense that the program knows inadvance how many times the loop is to be executed.
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The Selective Structure : switch

The syntax of the switch instruction is a bit peculiar. Its objective is to check several possible constant values for an expression, something similar to what we did at the beginning of this section with the linking of several if and else if sentences. Its form is the following:
switch (expression)
{

case constant1:

block of instructions 1

break;

case constant2:

block of instructions 2

break; . . .

default: default block of instructions

} LEAN MORE>>

Program Control Statements

The program flow in high - level languages is sequential. A program is usually not limited to a linear sequence of instructions. Therefore there is a use of control structures that serve to specify what to do with our program and how.
C++ provides statemets to perform efficiently and effectively. Such statements are called program control statements. These are selection statements ( if and switch), iteration statements (for, while and do-while) and jump statements such as (return, goto, exit(), break and continue)
Statements
Statements are instructions given to the computer to perform an action such as moving data, taking decisions or repeating actions. LEARN MORE>>

Precedence of Operators

Precedence and associativity are the two important properties of operators. Precedence is the order in which a program performs / evaluates the operation in a formula. All operators have a precedence value. An operator with higher precedence is evaluated before an operator with a lower precedence value.
When making complex expressions with several operands, we may have some doubts about which operand is evaluated first and which later. For example, in this expression:
a = 5 + 7 % 2 LEARN MORE >>

Operators & Expressions in C++

Introduction
An operator is a symbol or letter which makes the compiler perform a specific operation on operands (variables) in a program.
An expression is a combination of operands ( i.e, constants, variables, numbers), and operators that perform a specific operation and parenthesis.
An expression is a sequence of operators that specifies a computation. an expression may result in a numerical value.
For example: x+y is an expression in which the sign + is an operator which specifies the addition operation. LEARN MORE >>

Structure of a C++ Program

The structure of a C++ program is as described below:-
1. At the top of the program header files are declared.
2. A C++ prgram starts executing from main() function. The body of the main function is included with surly braces.
3. Each of the statment of the C++ program must end with a semicilon. a semicilon is also known as statement terminator.
So my first program would probably be:- LEARN MORE>>

Use of I/O Operators

INPUT / OUTPUT statements of C++ can be used for input of data from an input device such as a keyboard or to obtain output on output devices such as VDUs and printers.
In C++, input/output devices are treated as files; files are treated as a sequence or a stream of bytes. In other words, a stream in C++ means a flow of bytes from an input device to the CPU(input stream) and from the CPU to an output device (output stream).
Streams used for input and output are: LEARN MORE >>