Page 20 - Computer Science V2.0 Class 11

1.3.4 Speakers/Headphones
A speaker or a headphone generates sound as output. A computer typically requires specialised hardware (a sound
card) to provide output in the form of sound.

Monitor

Speakers Headphones
Output Devices

Plotter Printer
Fig 1.5: Output Devices

A 3D printer allows for making a three-dimensional solid object from a digital file.

1.4 Memory Unit

A computer system's memory unit (also called a storage unit) is used to store data and instructions.

1.4.1 Units of Memory

The data is stored and processed in a computer using binary digits, often abbreviated as bits: 0 and 1. Thus a bit is the
basic unit of memory. Bits are grouped to form larger units of information. For example, a sequence of four bits forms
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a nibble. As each bit in a nibble can be 0 or 1, four bits lead to 16 (=2 ) different nibbles: 0000, 0001, 0010, 0011, 0100,
0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111. Thus, a nibble can express a number between 0
and 15. A sequence of eight bits forms a byte. Again, as each bit in a byte can be 0 or 1, a byte can express 256 (=2 )
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different sequences. Thus, a byte is used to express a number between 0 and 255. The bytes can be further grouped
to form bigger units of memory. Table 1.1 shows different units of memory.
1 Bit = Binary Digit
8 Bits = 1 Byte
1024 Bytes = 1KB [KiloByte]
1024 KB = 1MB [MegaByte]
1024 MB = 1GB [GigaByte]
1024 GB = 1TB [TeraByte]
1024 TB = 1PB [PetaByte]
1024 PB = 1EB [ExaByte]
1024 EB = 1ZB [ZettaByte]
1024 ZB = 1YB [YottaByte]
1024 YB = 1 BrontoByte
1024 BrontoByte = 1 GeopByte
Table 1.1: Units of Memory

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