Codes in digital and computer fundamentals
Answers
Computer Fundamentals
Generation of Computers
Types of Computers
Characteristics
Block Diagram
CPU
Motherboard
RAM
ROM
Ports
Connectors
Cables
Slots and Cards
Bus Lines
Optical Disk Drive
Electronics
Electronic Components
Measuring Instruments
Number System
Binary Number System
Octal Number System
Decimal Number System
Hexadecimal Number System
Digital Codes
Logic Gates
Flip-Flops
Mulitplexer-Demultiplexer
Adders
Input Devices
Keyboard
Mouse
Touch Screen
Trackball & Joystick
Microphone
Webcam
Scanning Devices
Bar Code Reader
Recognition Devices
Output Devices
Monitor
Printer
Speaker
Storage Devices
Hard Disk
Compact Disc
Digital Video Disc
Pen Drive
Memory Card
Portable Hard Disk
Powering Devices
SMPS
UPS
Digital Codes
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Computers and digital circuits processes information in the binary format. Each character is assigned 7 or 8 bit binary code to indicate its character which may be numeric, alphabet or special symbol. Example - Binary number 1000001 represents 65(decimal) in straight binary code, alphabet A in ASCII code and 41(decimal) in BCD code.
Types of codes
BCD (Binary-Coded Decimal) code :
Four-bit code that represents one of the ten decimal digits from 0 to 9.
Example - (37)10 is represented as 0011 0111 using BCD code, rather than (100101)2 in straight binary code.
Thus BCD code requires more bits than straight binary code.
Still it is suitable for input and output operations in digital systems.
Note: 1010, 1011, 1100, 1101, 1110, and 1111 are INVALID CODE in BCD code.
ASCII (American Standard Code Information Interchange) code :
It is 7-bit or 8-bit alphanumeric code.
7-bit code is standard ASCII supports 127 characters.
Standard ASCII series starts from 00h to 7Fh, where 00h-1Fh are used as control characters and 20h-7Fh as graphics symbols.
8-bit code is extended ASCII supports 256 symbols where special graphics and math's symbols are added.
Extended ASCII series starts from 80h to FFh.
EBCDIC (Extended Binary Coded Decimal Interchange Code) code
8-bit alphanumeric code developed by IBM, supports 256 symbols.
It was mainly used in IBM mainframe computers.
Gray code
Differs from leading and following number by a single bit.
Gray code for 2 is 0011 and for 3 is 0010.
No weights are assigned to the bit positions.
Extensively used in shaft encoders.
Excess-3 code
4-bit code is obtained by adding binary 0011 to the natural BCD code of the digit.
Example - decimal 2 is coded as 0010 + 0011 = 0101 as Excess-3 code.
It not weighted code.
Its self-complimenting code, means 1's complement of the coded number yields 9's complement of the number itself.
Used in digital system for performing substraction operations.
Tip Box
Error dectecting and correcting schemes
Repetition codes
Parity bits
Checksums
Cyclic redundancy checks (CRCs)
Cryptographic hash functions
Error-correcting codes
Error correction
Automatic repeat request
Error-correcting code
Hybrid schemes