DATA MEASUREMENT..

The relationship of data representation

Bit - A bit is the smallest unit of data that the computer can process. Bit is a short for binary digit. A bit is represented by the numbers 1 and 0. These numbers represent the binary system. They correspond to the states of on and off, true and false, or yes and no. All digital data use the binary system to process the information. This information includes letters, digits or special character.

Byte - Byte is a unit of information built from bits. One byte is equals to 8 bits. Eight bits that are grouped together as a unit. A byte provides enough different combinations of 0s and 1s to represent 256 individual characters. One byte represents a single character such as the number 3, letter b or a $ symbol. Bits and bytes are the basis for representing all meaningful information and programs on computers.

Character - Computers does not understand letters, numbers, pictures or symbols. Computers uses binary system to count only as it only recognizes two states that are 0 and 1. A byte represents a single character in the computer. One character such as A, 7, 9 and + is eight bits that are grouped together. A byte provides enough different combinations of 0s and 1s to represent 256 individual characters. For example, the capital letter F is represented by the binary code 01000110 that can be understood by the computer system.

Coding Scheme

The combinations of 0’s and 1’s are defined by patterns. These patterns are called coding system or schemes. There are three character codes or coding schemes to represent characters which are ASCII,EBCDIC and Unicode. ASCII is most widely used for personal computers. EBCDIC was developed by IBM and is used primarily for large computers like mainframes and high end servers.

The 256 character capability of ASCII and EBCDIC is to small to handle characters that are used by other languages such as Arabic, Japanese and Chinese. The Unicode coding system are designed to solve this problem. It uses two bytes (16bits) combination to represent one character. This gives it capability to represent 65,536 different characters. This can cover all the world’s languages. Unicode is downward-compatible with ASCII meaning that Unicode can recognize ASCII

ASCII (American Standard Code for Information Interchange) was established to:

• To make it possible for humans to interact with a digital computer that processes only bits.
• achieve compatibility between various types of data processing equipment making it possible for the components to communicate with each other successfully.
• enables manufacturers to produce components that are assured to operate correctly in a computer.
• make it possible for humans to interact with a computer. It also enables users to purchase components that are compatible with their computer configurations

Units of data measurement

Bit - A bit is represented by the numbers 1 and 0. They correspond to the states of on and off, true and false, or yes and no.

Byte - 1 byte = 8 bit

Kilobyte (KB) - 1 KB = 1024 bytes or 1 KB = 2¹⁰ bytes

Megabyte (MB) - 1 MB = 1 048 576 bytes or 1 MB = 2²⁰ bytes

Gigabyte (GB) - 1 GB = 1 073 741 824 bytes 1 GB = 2³⁰ bytes

Terabyte (TB) - 1 TB = 1 099 511 627 776 bytes or 1 TB = 2⁴⁰ bytes

Note:

1 KB = 1 024 byte

1 MB = 1 024 KB = 1 048 576 byte

1 GB = 1 024 MB = 1 048 576 KB = 1 073 741 824 byte

1 TB = 1 024 GB = 1 048 576 MB = 1 073 741 824 KB = 1 099 511 627 776 byte

Units of clock speed measurement

Clock speed or computer speed means how fast a computer can process data. In other words, this means the speed the computer can turn data into information. It is measured by a system clock that is situated in the microprocessor.

The clock speed is measured in hertz which means once machine cycle per second. The speed of the system clock has no effect on the speed of printers or disk drives.

The combination of speed and number of paths determines the total processing speed or channel bandwidth as it is sometimes referred to. This is because different processors use different architecture.

For example:-

1.4 GHz Pentium 3à 1.4 GHz Pentium 4à 1.4 GHz Power PC G4

Hertz & Seconds

· A hertz is one cycle per second.

· Megahertz (MHz) – 1 Megahertz (MHz) equals to one million cycles of the system clock. (Mega is a prefix that stands for million. A computer that operates at 933 MHz has 933 million clock cycles in one second.)

· Gigahertz (GHz) -1 Gigahertz (GHz) equals to one billion cycles of the system clock. In relation with megahertz, 1.0GHz is equivalent to 1000 MHz. Giga is a prefix that stands for billion. GHz is most often used as a measurement of a PC processor chip and power, with bigger numbers meaning more speed and higher price. A microprocessor that runs at 200 GHz executes 200 billion cycles per second. For a 2.4 GHz machine . Its clock rate is 2.4 billion cycles per second.)