The logic circuits of digital computers are binary, that is, they can at any one time be in one of only two states.

Thus, the only information that can be represented is that which is adequately represented with only two values – say whether a switch is on or of, a person is male or female.

The two states of a binary device are usually represented by the binary digits (bits) 0 and 1.

So the computer store and manipulate data in the form of 0’s and 1’s whereas humans have ten fingers and count by using decimal number system that uses ten decimal digits from 0 to 9.

Concept of Bit and Byte:

§  When referring to computerized data, each switch- whether it is on or off is called a bit.

§  The term bit in itself is contraction of binary digit.

§  A bit is the smallest possible unit of data.

§  A bit has a single binary value, either 0 or 1.

§  The computer needs group of bits to represent anything meaningful, that is, to convey information.

§  Because a single bit is not sufficient to represent data. It has become necessary to work with group of eight bits.

§  Each group of eight bits called Byte.

§  A byte can be used to represent one character of data which may be number, an alphabet or any other special character.

§  With one Byte computer can represent 256 different values because it is possible to count from 0 to 255 with 8 binary digits, that is: 00000000 means 0 and 11111111 means 255

§  Byte is an extremely important unit because there are sufficient different eight bit combinations to represent all the characters on the keyboard, including all the letters, numbers, punctuation marks and other symbols.

§  When user types a character on keyboard, a specific bit pattern is electronically transferred to money.

§  To represent large number and string of characters, bytes are combined to represent the words.

§  Each word of storage is assigned unique address in memory.

§  Microcomputers generally used word length of 2 bytes or 4 bytes or even 8 bytes.

§  The capacity of memory is generally expressed in terms of letter Kor KiloByte, which equals approximately 1024 bytes.

§  1 BYTE = 8 BITS.

§  1 KB = 1024 BYTES.

§  1 MB = 1024 KB.

§  1 GB = 1024 MB.

§  1 TB = 1024 GB.

Concept of Field:

§  A field is a meaningful collection of related characters.

§  It is the smallest logical data entity that is treated as single unit in data processing.

§  Generally there are three types of fields: alphabetic, numeric and alphanumeric.

§  for example, if we are processing employees data of a company, we may have an employee code field, name field, an hourly pay field, a tax deduction field etc.

Concept of Record:

§  Fields are generally grouped together form a record.

§  A record is then a collection of fields that are treated as single unit.

§  An employee record would be a collection of fields of one employee.

§  These fields would include employee’s code, name number of hours worked, pay rate and so farth.

Concept of File:

§  Records are then grouped to form a file.

§  A file is a collection of number of related records that are treated as a unit.

§  For example, collection of all employee records for one company would be an employee file.

§  Similarly, collection of all inventory records for a company forms an inventory file.

§  It is customary to set up a master file of permanent data and to use transaction file containing data of temporary nature.

Concept of Database:

§  It is collection of logically related data elements that may be structured in various ways to meet multiple processing and retrieval needs of organisation and individuals.

§  Database is a collection of integrated and related master files.

§  It does not imply that all the data related to a company’s business should be contained on a single database.

§  But simply that all records in a database should be related and redundant data should be minimized.

§  The general objectives in establishing a database are: Eliminate redundant data as much as possible.

§  Integrate existing data files

§  Share data among all users

§  Simplify the use of data files

§  Incorporate changes easily and quickly

§  Minimize the cost of storing and retrieving data.

§  Improve accuracy and consistency

§  Provide data security from an unauthorized use.

§  Exercise central control over standards


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