What is meant by encoding of data? Explain different coding schemes to represent data in computer.
Computer works only with binary numbers. It stores all types of data in the form binary digits. The data is converted to binary form before it is stored inside the computer the process of converting data into binary form is known encoding. Data can be converted into binary form by using different coding schemes.
Types of coding schemes
Different types of coding schemes are as follows:
1. BCD Code
BCD stands for binary coded decimal. It is a 4-bit code. It means that each decimal digit is represented by 4 binary digits. It was used by early computers.
2. EBCDIC Code
EBCDIC stands for extended binary coded decimal interchange code. It is an 8-bit code. It is normally used in mainframe computers. It can represent 256 characters.
ASCII stands for American standard code for information interchange. It was published in 1968 by ANSI (American National Standard Institute). It is the most widely used coding scheme for personal computers. The 7-bit code can represent 128 characters. It is not enough to represent some graphical characters displayed on computer screens. An 8-bit code can represent 256 characters. The extended 128 unique codes represent graphic symbols.
Unicode is a 16-bit code. It can represent 65536 characters. It has started to replace ASCII code. It can represent the characters of all languages in the world.
What is data transmission mode? Explain its types with example.
The way in which data is transmitted from one place to another is called data transmission mode.
Types of transmission modes
There are three types of data transmission modes:
- Simplex mode 2. Half duplex mode 3. Full duplex mode
1. Simplex mode
In simplex mode, data can flow only in one direction. It cannot be moved in both directions. It operates in a manner similar to a one-way street. The direction of flow never changes. A device with simplex mode can either send or receive data. It cannot perform both changes. A device with simplex mode can either send or receive data. It cannot perform both actions.
Figure: simplex mode
An example is a traditional television broadcast. The signal is sent from the transmitter to TV antenna. There is no return signal.
2. Half-Duplex Traffic
In half-duplex mode, data can flow in both directions but not at the same time. It is transmitted one-way at one time. A device with half-duplex mode can send or receive data but not at the same time. That is why the speed of half-duplex mode is slow.
Figure: Half Duplex
Internet surfing is an example of half-duplex communication. The user issues a request for a web page. The web page is downloaded and displayed before the user issues another request.
3. Full-Duplex Mode
In full-duplex mode, data can travel in both directions simultaneously. Full duplex mode is a faster way of data transmission as compared to half duplex. Time is not wasted in changing the direction of data flow.
Figure: Full Duplex
A telephone is a full-duplex communication is automobile traffic on a two-lane road. The traffic can move in both directions at the same time.