# Digital Number System

A digital system can understand positional number system only where there are a few symbols called digits and these symbols represent different values depending on the position they occupy in the number.

A value of each digit in a number can be determined using

• The digit

• The position of the digit in the number

• The base of the number system (where base is defined as the total number of digits available in the number system).

## Decimal Number System

The number system that we use in our day-to-day life is the decimal number system. Decimal number system has base 10 as it uses 10 digits from 0 to 9. In decimal number system, the successive positions to the left of the decimal point represents units, tens, hundreds, thousands and so on.

Each position represents a specific power of the base (10). For example, the decimal number 1234 consists of the digit 4 in the units position, 3 in the tens position, 2 in the hundreds position, and 1 in the thousands position, and its value can be written as

```(1×1000) + (2×100) + (3×10) + (4×l)
(1×103) + (2×102) + (3×101)  + (4×l00)
1000 + 200 + 30 + 1
1234
```

As a computer programmer or an IT professional, you should understand the following number systems which are frequently used in computers.

S.N. Number System & Description
1 Binary Number System

Base 2. Digits used: 0, 1

2 Octal Number System

Base 8. Digits used: 0 to 7

3 Hexa Decimal Number System

Base 16. Digits used: 0 to 9, Letters used: A- F

## Binary Number System

Characteristics

• Uses two digits, 0 and 1.

• Also called base 2 number system

• Each position in a binary number represents a 0 power of the base (2). Example: 20

• Last position in a binary number represents an x power of the base (2). Example: 2x where x represents the last position - 1.

### Example

Binary Number: 101012

Calculating Decimal Equivalent −

Step Binary Number Decimal Number
Step 1 101012 ((1 × 24) + (0 × 23) + (1 × 22) + (0 × 21) + (1 × 20))10
Step 2 101012 (16 + 0 + 4 + 0 + 1)10
Step 3 101012 2110

Note: 101012 is normally written as 10101.

## Octal Number System

Characteristics

• Uses eight digits, 0,1,2,3,4,5,6,7.

• Also called base 8 number system

• Each position in an octal number represents a 0 power of the base (8). Example: 80

• Last position in an octal number represents an x power of the base (8). Example: 8x where x represents the last position - 1.

### Example

Octal Number − 125708

Calculating Decimal Equivalent −

Step Octal Number Decimal Number
Step 1 125708 ((1 × 84) + (2 × 83) + (5 × 82) + (7 × 81) + (0 × 80))10
Step 2 125708 (4096 + 1024 + 320 + 56 + 0)10
Step 3 125708 549610

Note: 125708 is normally written as 12570.

Characteristics

• Uses 10 digits and 6 letters, 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F.

• Letters represents numbers starting from 10. A = 10, B = 11, C = 12, D = 13, E = 14, F = 15.

• Also called base 16 number system.

• Each position in a hexadecimal number represents a 0 power of the base (16). Example 160.

• Last position in a hexadecimal number represents an x power of the base (16). Example 16x where x represents the last position - 1.