Number System

Number system is a set of values used to represent different quantities and other special characters. In other words it is a system of number that deals about the numbers and their representation(such as base and exponents) in different systems.

Number system have been around for thousands of years. The common system is the existing system based on number ten(10). Apart from this number system, there are in use the Arabic system, binary system(base two), ternary system(base three), quaternary system(base four), quinary system(base five), octal system(base eight), decimal system(base ten), due-decimal system(base twelve), hexadecimal system(base sixteen),etc.

All these number system can be used to count the number of students in a class or number of viewers watching a certain TV program etc.

The number systems can be categorized in two categories:

1. Non-Positional Number Systems

2. Positional Number Systems

 

 1. Non-Positional Number Systems

In ancient time, people used to count on their fingers. When these fingers became insufficient for counting then stones, pebbles or sticks were used to signify the values. This method of counting is known as the Non-Positional Number System. It was very difficult to perform arithmetic operation, and it had no symbol for zero. The most common non-positional number system is the Roman Number System. In this number system, only a few characters are used to represent the numbers. The characters that are use in this number system are I,V,X,L(fifty),C(hundred),D(thousand),etc. Furthermore, it is very difficult to perform arithmetic operation, logical operation as well as positional techniques.

 

 2. Positional Number Systems

In positional number system, the value of each digit in a number is defined not only by the system but also by the position of symbol. Positional number system have a base or radix. The first positional number system was invented by the Babylonians. They used a base 60 system. The positional number system, which is being used nowadays is known as the decimal number system. The system is base ten(10) system that contains ten(10) digits 0,1,2,3,4,5,6,7,8,9. 

The digital computer represents all kinds of data and information in binary numbers 0 and 1. It includes audio, graphics, video, text and number. Actually to a computer everything is a number. Numbers are numbers, letters are numbers, sound and pictures are also numbers. Even the computer's own instructions are numbers. Computer represents alphabets in ASCII code(American Standard Code for Information Interchange).

Input Devices

Input Devices: A peripheral device that is used for entering data and instructions into the computer is known as Input device. Commonly used input devices are keyboard, mouse & touchpad. Computer may have some other i/o devices like web camera, microphone, touch screen, joystick, scanner & light pen.

Keyboard: Keyboard is input device which is used for entering data & instruction like letters, texts, a number, symbols & commands. It looks like a typewriter which contains a number of keys marked with alphabets, numbers & some other characters. Standard keyboard has 104 keys. Multimedia keyboard has more than 104 keys. Computer understands only binary codes, so when you press a key on the keyboard, the keyboard generates the related binary code & sends to the computer. Eg:- When we press an alphabet key "A", a keyboard generates binary code '01000001'.

Alphabet Keys: Alphabet keys are labelled with A to Z & punctuation symbols. The alphabet keys are used to enter alphabet & punctuation marks. We can enter capital alphabets(A to Z) using alphabet keys.

Numeric keys: Numeric keys are labelled with numbers from 0 to 9 & mathematical symbols +, -,*,/,. . The numeric keys are used for entering numbers & mathematical symbols.

Cursor movement keys:  Cursor movement keys are labelled with arrows signs. They are used to move the cursor to the specified directions. The cursor movement keys are also known as arrow keys.

Function Keys:  Function keys are labelled as F1,F2,F3, till F12. The function keys are used to enter commands.

Special purpose keys: Special purpose keys are shift, enter, ctrl, alt & del. A standard computer keyboard contains 104 keys. A multimedia computer keyboard has more than 104 keys.

Mouse: In GUI environment, we can input data & instruction into the computer which are seen on the window with the help of mouse. We can apply commands or open disk drives, files or folders by using a computer mouse.

Mouse is a small hand held input device that looks like a mouse. It is used for selecting file, folder & icon on a desktop or command on a menu. It is also used for drawing lines curves & freehand shapes.

It consists of plastic casing with a flat bottom & has two or three buttons on the top of casing. The middle button may be the scrolling button. On the flat surface of a mouse there may be a ball projected outside from a hole or loser projection hole. The left button of the mouse works like the enter key & right button displays the control menu. When we move a computer on the mouse pad, the mouse pointer on the screen moves accordingly. We can point out the command, file or folders or other items on the screen & select it by clicking the left mouse buttons. Since it points file, folder, command or items on the screen, it is also called a pointing device.

Touch Pad: A touch pad is a touch sensitive pad. It is used instead of mouse in laptop computers. It has two buttons which work like mouse left & right buttons. When we move our finger touching the pad, it moves the mouse pointer on the screen. So, we can select file, folder or other items on the desktop & input necessary commands.

Joystick: A joystick is an input device. It is specially used in playing games in computer. It controls the movement of cursor & allow us to select options or facilities of games. It is like a stick having one or more push buttons. The push buttons of the joystick are called triggers. The stick of joystick can be moved in any direction or angle &controls the movement of a mouse pointer.

Microphone: A microphone(also known as mic or mike) is an input device used for entering audio , sound or voice in a computer. The input sound or voice can be saved in a computer as a sound file. Nowadays michrophone is used to input texts or commands.

Web Cam: A web cam or web camera is an input device which captures pictures or videos & transfers into the computer as digital image or videos file. It is used for video chatting programs like Viber, messenger, Facebook, Skype,etc.

Scanner: Scanner is an input device that converts text (hand written or printed one) or pictures as digital image & transfer to the computer. These types of image files can be modified or edited using software like Adobe Photoshop, CorelDraw,etc.

It works like a photocopy machine. It has 2 components. First one illuminates the text or pictures & captures the optical images. Second one converts optical image into digital format & transfer to computer.

There are 2 types of Scanners

1. Handheld scanner
2. Flatbed scanner  

  

Computer Components

The Computer Case:

                       The computer case or chassis , is usually constructed of metal, holds all the primary electronic components of the computer & most of the drives. The case provides access to other devices via ports & connectors, & protects surrounding devices such as TVs, mobile, speakers etc, from the computer's EMI .

                          The size & configuration of the case that should be considered as follows:

• The bigger the case, the more components it can hold. This provides greater expansion potential. Bigger cases also provides better air flow which is essential for cooling & large cases are easier to work with.
• The more compact the case or chassis, the less or low expansion potential it has; working on it is often much more difficult & usually air flow is more restricted or blocked.
• Smaller cases or chassis that come with a power supply usually have lower wattage which results in reduction of number of internal devices that can be installed.
• The more features in a case or chassis design, like the power wattage or the number of bays, the more higher the cost.

Power Supply:

                  A power supply provides an electrical power to the computer components. It draws power from local alternating current(AC) source such as a wall outlet & converts it to either 3.3 or 5 volts Direct Current(DC) for on board electronic components or devices & 12 volts DC for motors & hard disk drives. It delivers both positive & negative direct current to the computer. Power supplies must also 'condition' the power input i.e. it must smooth out any radical changes in the quality of the electrical supply as many homes & offices have power that fluctuates for more than the delicate computer components can tolerate. If the fan should fail or cause the computer to behave erratically, the power supply must be replaced when replacing a power supply, there are three things to consider physical size, wattage & connectors. There are devices that can be used to protect the computer from power supply problems. These includes surge suppressors & un-interruptible power supplies (UPS).

Surge Suppressors:

                    A surge suppressor can be used to filter out the effects of voltage spikes & surges that are present in commercial power sources & smooth out power variations. However, almost nothing will shield a computer from a very close lightning strike. Surge suppressors are available from local computer dealers & superstores. Most power stripes within surge protection have a red indicator lights. If the light goes out it means that the unit is no longer proceeding protection & needs to be replaced. If the indicator light starts flashing, it means the power strip is failing & should be replaced immediately. Surge suppressors smooth out power variations & protects the computer from power fluctuations up to a point, however, for a complete protection from power fluctuation & outage, an uninterruptible power supply (UPS) is recommended.

Uninterruptible Power Supply (UPS):

                   A uninterruptible power supply is an inline battery backup that is installed between a computer & the wall outlet. A UPS protects the computer from surges & acts as a battery when the power dips or fails. It also provides a warning when the power source is above or below acceptable levels. Many UPS models can interact with the computer and initiate a safe shutdown in the event of a complete power failure. UPS device will need its own line & circuit breaker. One of the principal power drains is a monitor. To keep a system online as long as possible during or at a time of power failure, turn off the monitor immediately after the failure commences or occurs. When considering a UPS , we must take into account the amount of protection that is need. The watt rating of the UPS must be sufficient to supply the computer & all its peripherals with power for enough time to safety shut down the system.

Motherboards :

                      The motherboard serves as the computer's back bone. All devices in a computer are connected to it in some way(direct or indirect way); it hosts the largest single collection of chips of any computer component & links all the components, making it possible for them to communicate. The motherboard also defines the computers limits of speed, memory & expand-ability.The motherboard is usually the largest circuit board that is usually found inside the computer case or chassis. Motherboards come in a number of sizes or form factors of which AT & ATX form factor are the two main varieties.

 The CMOS Battery:

                     The CMOS chip requires a small or few amount of voltage from a battery to retain its memory. When the battery get low or dies, the computer will experience a sudden memory less & thus settings. The voltage of CMOS battery ranges from 3 to 6 volts. The CMOS chip contain a capacitor that allows us to replace the battery without losing any data.

Power On Self Test:

                Every time a computer boot up or reset using the Reset button or the windows Restart command, the computer reboots & reset to its basic or the default operating conditions. The system BIOS program starts by invoking or executing a special program stored on ROM chip called Power-On-Self-Test (POST). The POST sends out or circulate the standardized commands that checks every primary devices in other words, it runs or executes an internal self diagnostic routine. The POST has two stages: one occurs before & during the text of the video of the other that occurs after the video has been tested . The division determines whether the computer will alert you to errors by beeping or showing them on the screen.