Page 96 - DCAP516_COMPUTER_SECURITY

Computer Security

Notes Its contents are analyzed and evaluated.
It is placed in a proper context for a human user.
Data is typically manipulated by activities such as calculating, comparing, sorting, classifying
and summarizing. These activities involves organizing, analysing, manipulating and converting
data into information for users. These qualities of any data stored in an information system,
must also be maintained by a continual process of correcting and updating activities.

8.2 Data Hierarchy

The components of the data hierarchy in an information system are listed here in ascending
order of complexity:

1. Bit: The term, bit, is short form for binary digit. It can assume either of two possible states
and therefore can represent either 0 or 1. In secondary storage, a bit is used to represent
data through positive or negative polarity of an electrical charge on a magnetic recording
medium such as tape or disk. Semi-conductor storage is usually used for primary storage.
In semiconductor storage, a bit is represented by an electrical circuit that is either
conducting or not conducting electricity.
2. Byte: The ability to represent only binary digits (bits) in a computer system is not sufficient
for business information processing. Numeric and alphabetic characters as well as wide
variety of special characters such as dollar signs, question marks, and quotation marks,
must be stored. In a computer system, a character of information is called a byte.

Notes A byte of information is stored by using several bits in specified combination
called bit patterns. One widely used bit pattern for personal computers and data
communications is the American Standard Code for Information Interchange (ASCII).
ASCII uses seven bits to represent one character. Each 1 or 0 corresponds to a single bit.
3. Field: The next level in the data hierarchy is a field or item of data. A field or item of data
is one or more bytes that contain data about an attribute of an entity in the information
system. An entity in a payroll system is an individual employee. Attributes are the
employee’s name, pay rate, and so on. The basic pay is a field or item of data.
4. Record: A record is a collection of fields relating to a specific entity. For example, a payroll
record contains fields of data relating to a specific employee. An analogy can be made
between a computer-based record and an individual folder in a manual file. A folder in a
payroll file may contain much the same information as a record in a computerized payroll
file. The field that identifies a record from all other records in a file is the record key. For
example, the record key in a payroll record is usually the employee’s provident fund
number or social security number because it is different for each employee.
5. File: A file is a collection of related records. For example, the collection of payroll records
for all employees in a company is a payroll file. The concept of a computer file is very
similar to a manual file in a filing cabinet.
6. Data Base: A database consists of all the files of an organization, structured and integrated
to facilitate update of the files and retrieval of information from them. The term has often
been used rather loosely. Technically, a database consists of those files that are part of a
data base management system. However, database is often used to refer all the files of an
organization.

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