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Decimal Number System
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Decimal Number System

Last Updated : 09 Apr, 2025
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A number system is a method of representing numbers. Every number system is identified with the help of its base or radix. For example, Binary, Octal, Decimal and Hexadecimal Number systems etc. If the Base value of a number system is 10. This is also known as base-10 or Decimal number system which has 10 characters from 0 to 9.

This is the weighted (or positional) number representation where value of each digit is determined by its position (or their weight) which is a power of 10 in a decimal number. Each position in the decimal system is 10 times more significant than the previous position, that means the numeric value of a decimal number is determined by multiplying each digit of the number by the weight of the position in which the digit appears and then adding the products.

Example:

The number 2020 is interpreted as:

2020 = (2 × 10³) + (0 × 10²) + (2 × 10¹) + (0 × 10⁰) = 2000 + 0 + 20 + 0 = 2020

Decimal to Binary Conversion

Example :

The number 2020 in binary notation:

(2020)10 = (____)2

= (2020)10 = (1024 + 512 + 256 + 128 + 64 + 32 + 4)10 = (210x1 + 29x1 + 28x1 + 27x1 + 26x1 + 25x1 + 24x0 + 23x0 + 22x1 + 21x0+ 20x0)10 = (11111100100)2

Note : Right most bit is the least significant bit (LSB) and left most bit is the most significant bit (MSB).

The range in Decimal number system expressed as their corresponding binary number.

Decimal Number

Binary Number

00
11
210
311
4100
5101
6110
7111
81000
91001

Also read about:

  1. Decimal to Binary Conversion and its implementation.
  2. Decimal to Octal Conversion and its implementation.
  3. Decimal to Hexadecimal Conversion and its implementation.

9’s and 10’s Complement of Decimal (Base-10) Number

Complements are used in number systems to simplify subtraction and error detection in digital systems. In the decimal system, the 9’s complement and 10’s complement are commonly used.

Steps to Find 9’s Complement:

  1. Write the given decimal number.
  2. Subtract each digit from 9.

Example : 9’s Complement of 2020

 9 - 2 = 7  9 - 0 = 9  9 - 2 = 7  9 - 0 = 9

Thus, the 9’s complement of 2020 is 7979.

Steps to Find 10’s Complement:

  1. Find the 9’s complement of the number.
  2. Add 1 to the least significant digit (LSB).

Example 1: 10’s Complement of 2020

  • 9’s complement of 2020 = 7979
  • Adding 1: 7979 + 1 = 7980

Thus, the 10’s complement of 2020 is 7980


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Decimal Number System

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