how to working mobile,calculator and computer keyboard.

                  COMPUTER KEYBOARD 

A binary code represents text, computer processor instructions, or any other data

using a two-symbol system. The two-symbol system used is often the binary number

system's 0 and 1. The binary code assigns a pattern of binary digits, also known as

bits, to each character, instruction, etc. For example, a binary string of eight bits can

represent any of 256 possible values and can therefore represent a wide variety of

different items.

In computing and telecommunications, binary codes are used for various methods of

encoding data, such as character strings, into bit strings. Those methods may use fixed-width or variable-width strings. In

a fixed-width binary code, each letter, digit, or other character is represented by a bit string of the same length; that bit

string, interpreted as a binary number, is usually displayed in code tables in octal, decimal or hexadecimal notation. There

are many character sets and many character encodings for them.

A bit string, interpreted as a binary number, can be translated into a decimal number. For example, the lower case a, if

represented by the bit string 01100001 (as it is in the standard ASCII code), can also be represented as the decimal number 97. 

                             CALCULATOR KEYBOARD 

The ANITA Mark VII and ANITA Mark VIII calculators were

launched simultaneously in late 1961 as the world's first all-electronic

desktop calculators. Designed and built by the Bell Punch Co. in

Britain, and marketed through its Sumlock Comptometer division,

they used vacuum tubes and cold-cathode switching tubes in their

logic circuits and nixie tubes for their numerical displays.

They were the first of a series of desktop and hand-held electronic

calculators that the company was to develop and sell under the

ANITA name into the mid-1970s.

            PUNCH CARD 

A punched card or punch card is a piece of stiff paper that can be used to contain digital data represented by the

presence or absence of holes in predefined positions. Digital data can be used for data processing applications or, in earlier

examples, used to directly control automated machinery.

Punched cards were widely used through much of the 20th century in the data processing industry, where specialized and

increasingly complex unit record machines, organized into semiautomatic data processing systems, used punched cards

for data input, output, and storage. Many early digital computers used punched cards, often prepared using keypunch

machines, as the primary medium for input of both computer programs and data.

While punched cards are now obsolete as a storage medium, as of 2012, some voting machines still use punched cards to

record votes.

              Machines are check that OMR mark-sheet