Computer Speed and Measurement Unit | HSEB Notes on Computer Science Class 11

Computer Science
HSEB Notes on Computer speed and Measurement Unit
Class : 11

Space measurement units

The size of device in computers does not reflect the space available to store data in it. There are larger devices that can store only a few data where as many tiny devices that stores unbelievable amount of data. Because how long, how thick etc cannot determine how much we can store inside, we need to find some other way to measure space. Almost all of the computers use binary numbering systems (though there are some exceptions). Binary numbering system consists of only two digits – 0 and 1 to represent any quantity. 10 in binary is equal to the 2 and 100 to 5. We will be learning this numbering system after some days.

Everything in computers is represented in strings of binary numbers. For example capital A is interpreted by computer as 0100 0001 and B is 0100 0010. All characters, numbers, symbols, images, sounds, animations, videos and everything, yes everything is converted into suitable binary code to store in computer or process by computer. So if there is any device that can store one binary digit (whether 0 or 1), its storage capacity is 1 bit. We’ve already learned that bit is the abbreviation of binary digit. Any device that has storage space to accommodate 5 binary digits has 5 bits space. 

You require thousands and millions of bits for a file and expressing the space available in bits only is really inconvenient because it will be an extremely large number. So, we have larger units that represent a group of lower units. A group of 4 binary digits is called a nibble (4 bits = 1 Nibble). Similarly a group of 8 bits is called a byte (1 byte = 8 bits). As you have seen the example above, each character requires 8 bits which is 1 byte. So 1 character requires 1 byte space. Now, if you have a text file whose size is 32 bytes, it means there are 32 x 8 binary digits (0s and 1s) stored in it. In the metric system 1000 lifts up the unit to the higher such as 1000 meter is 1 kilometer, 1000 liter is 1 kiloliter etc. In binary numbering system it is 1024 (=2 10) that converts to higher unit. Following table lists the different units and their values:

Space Measurement Units

Units                         Equivalent

0 or 1                            1 Bit

4 bits                             1 Nibble

8 bits                             1 Byte

1024 bytes                    1 Kilobytes (KB)

1024 Kilobytes              1 Megabyte (MB)

1024 Megabytes           1 Gigabytes (GB)

1024 Gigabytes            1 Terabytes (TB)

1024 Terabytes            1 Petabyte (PB)

1024 Petabytes            1 Exabyte (EB)

Speed Measurement Units

speed is related to time. Computer can perform millions of tasks in one second. So to compare the speed of computer operation (execution of programs and instructions) we require some units that can represent a very small fraction of time. Following are the units used to indicate fraction of seconds:

Speed Measurement Units

Units                                       Equivalent

1000 th of a second                   1 Milliseconds (MS)

1000 th of a milliseconds           1 Microseconds (μs)

1000 th of a microseconds        1 Nanosecond (ns)

1000 th of a nanoseconds         1 Picoseconds (ps)

1000 th of a picoseconds         1 Femtoseconds (fs)

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