Page 16 - Viva ICSE Computer Studies 3 : E-book

• Arithmetic and Logical Unit (ALU): It performs arithmetical
calculations like addition, subtraction, multiplication and

division. It also performs logical operations such as fi nding
the smaller or greater number between the given numbers.

Keyboard
A keyboard is the most common hardware device which is used to enter data into a

computer in diff erent forms.

We fi nd diff erent types of keys on the keyboard.
• Alphanumeric Keys: These keys are used to type letters and numbers. 26 alphabet

keys are arranged in a jumbled manner on a keyboard. There are 10 number keys
from 0 to 9.

• Special Keys: These keys are used to perform a specifi c task. The functions of some
special keys are discussed here.

 Backspace key erases text placed before the cursor and the text
selected by us.

 Delete key erases text placed after the cursor and the text selected by us.

 Enter key is used to type from a new line or to send the
cursor to the next line. It is also called the Return key.

 Space bar key moves the cursor ahead by one space. It gives space between two
letters, numbers or words. It is the longest key on the keyboard.

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