Basic concepts of computer, Essays (university) of Computer Fundamentals

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Basic Concepts of Computers

ELT2116/2216 - Computer

Applications

1

Number Systems

• A number system defines a set of values used to

represent quantity. For a computer, everything is a

number whether it may be numbers, alphabets,

punctuation marks, instructions, etc.

• Since the computer is an electronic device it can only

understand 1’s and 0’s which represents ‘on’ and ‘off’.

• A letter of an alphabet means a combination of

numbers to the computer. These are called binary

numbers/ digits.

Basic Concepts of Computers

ELT2116/2216 - Computer

Applications

2

Measuring memory capacity

• The basic unit of measuring memory capacity is ‘BYTE’
• 1 Byte = 8 Bits
• This is the amount of memory space needed to store a character, a number or other value.

ELT2116/2216 - Computer

Applications

4

• Bit = 1 or 0
• 1 Byte = 8 Bits
• 1 Kilobyte (KB) = 1,024 Bytes
• 1 Megabyte (MB) = 1,024 Kilobytes
• 1 Gigabyte (GB) = 1,024 Megabytes

ELT2116/2216 - Computer

Applications

5

Characteristics of binary

number system

• Uses two digits, 0 and 1.
• Also called base 2 number system
• first position in a binary number represents a 0 power of the base (2). Example 20
• Last position in a binary number represents a 𝑥 power of the base (2). Example 2 𝑥^ where 𝑥 represents the last position - 1.

ELT2116/2216 - Computer

Applications

7

How to Show that a Number is

Binary

• To show that a number is a binary number, follow it with a little 2 like this: 101 2
• This way people won't think it is the decimal number "101" (one hundred and one).
• What is the decimal form of 101 2? ELT2116/2216 - Computer

Applications

8

Decimal  Binary

5

2

1

101

ELT2116/2216 - Computer

Applications

10

2

2 ― 1

― 0

Exercise - 1

Convert following Binary numbers to Decimal a) 11001011 = 203 b) 00110101 = 53 c) 10000011 = 131 d) 10001111 = 143 e) 11100011 = 227 f) 00000100 = 4 g) 00010010 = 18 h) 00111111 = 63 i) 10101010 = 170 j) 01010101 = 85

ELT2116/2216 - Computer

Applications

11

Last week we learned two Number

systems:

• Binary (Base 2: 0,1)
• Decimal (Base 10: 0,1,2,3,4,5,6,7,8,9)
• Binary  Decimal
• Decimal Binary

This week……

• Octal (Base 8 : 0,1,2,3,4,5,6,7)
• HexaDecimal (Base 16 :

0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F)

• Binary for Computers
• Decimal for Humans
• Then why we need Octal and Hexadecimal

number systems?

• Longer binary numbers are what computers use at the

hardware level.

• But it is very difficult to learn and understand by a

human being.

• This is the reason for using octal, and more frequently

hexadecimal.

• Converting from these bases to binary is trivial, but the

numerals themselves will be human readable.

• It makes the communication between

programmers/architects and these machines we build,

easy.

• Generally in case of Graphics like color coding we can

use Hexadecimal number system.

Example

• (^1011010012)

1 0 1 | 1 0 1 | 0 0 1

x x x x x x x x x

2

2 2

1 2

0 2

2 2

1 2

0 2

2 2

1 2

0

5 5 1

= 551 8

Octal  Binary

• convert each digit of the octal number into its equivalent binary number.
• merge them into the same order they were when they were as octal numbers.
• omit the leftmost zeroes.