# Number Systems Digital Logic By: Safwan Mawlood

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Number Systems Digital Logic By: Safwan Mawlood
Digital Principles and Logic Design, A.Saha &N.Manna

Number Systems Knowing what base someone refers to
Decimal uses 10 digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. Binary uses 2 digits: 0 and 1. Octal number system there are 8 digits—0, 1, 2, 3, 4, 5, 6, and 7. Hexadecimal number system has 16 digits—0 to 9— and the rest of the six digits are speciﬁes by letter symbols as A,B, C, D, E, and F. Here A, B, C, D, E, and F represent decimal 10, 11, 12, 13, 14, and 15 respectively.

Base 10 Numbers

Base 2 (Binary) Numbers

Hexadecimal 1 2 3 4 5 6 7 8 9 A B C D E F The base 16, or hexadecimal (hex), number system is used frequently when working with computers, because it can be used to represent binary numbers in a more readable form.

CONVERSION BETWEEN NUMBER SYSTEMS
It is often required to convert a number in a particular number system to any other number system, e.g., it may be required to convert a decimal number to binary or octal or hexadecimal.

Converting Decimal to Binary
To convert a number in decimal to a number in binary we have to divide the decimal number by 2 repeatedly, until the quotient of zero is obtained.

Converting Decimal to Binary
Start by dividing the decimal by the largest number in the Value row that will go.

Decimal to Octal Conversion
Similarly, to convert a number in decimal to a number in octal we have to divide the decimal number by 8 repeatedly, until the quotient of zero is obtained.

The same steps are repeated to convert a number in decimal to a number in hexadecimal. Only here we have to divide the decimal number by 16 repeatedly, until the quotient of zero is obtained.

Binary-to-decimal Conversion
27 26 25 24 23 22 21 20 128 64 32 16 8 4 2 1

Converting 8-Bit Binary to Decimal
Binary numbers are converted to decimal numbers by multiplying the binary digits by the base number of the system, which is base 2, and raised to the exponent of its position.

Octal-to-Decimal Conversion
Ex. Convert into decimal number. Sol. The octal number given is 3462

Ex. Convert 42AD 16 to decimal

Fractional Conversion
Example: Convert into decimal number

Octal-to-decimal Conversion
Example: Convert into a decimal number.

Example: 42A.1216

-decimal-to-binary Conversion
Example:

Convert Decimal to octal number
Convert into an octal number.

Binary Subtraction

Example: Subtract and 10002

Binary Multiplication

Example: Multiply the following binary numbers 01112 and 11012

Example: Multiply the following binary numbers 1.0112 and 10.012

Binary Division

Example: Divide the following binary numbers 11001 and 101

1’s Complement The ones' complement of a binary number is defined as the value obtained by inverting all the bits in the binary representation of the number (swapping 0's for 1's and vice-versa).

Subtraction Using 2’s Complement
Binary subtraction can be performed by adding the 2’s complement of the subtrahend to the minuend. If a carry is generated, discard the carry. Now if the subtrahend is larger than the minuend, then no carry is generated

Integer Signed Unsigned 2’s Complement 5 0000 0101 4 0000 0100 3
2 1 -1 255 -2 254 -3 253 -4 252 -5 251 -35 100011 011100 011101

Code Computers and other digital circuits process data in binary format. Various binary codes are used to represent data which may be numeric, alphabetic or special characters. Codes are also used for error detection and error correction in digital systems.

Gray Gray code belongs to a class of code known as minimum change code, in which a number changes by only one bit as it proceeds from one number to the next.

Conversion of a Binary Number into Gray Code
(101011)2 change to Gray

Conversion of Gray Code into a Binary Number

Binary Code Decimal BCD, is a method of using binary digits to represent the decimal digits 0 through 9. A decimal digit is represented by four binary digits, or four bits are required to code each decimal number. as shown below:

You must realize that BCD and binary are not the same
You must realize that BCD and binary are not the same. For example, 4910 in binary is , but 4910 in BCD is BCD. Each decimal digit is converted to its binary equivalent.

BCD Conversion For example, let's go through the conversion of  to BCD. We'll use the block format that you used in earlier conversions. First, write out the decimal number to be converted; then, below each digit write the BCD equivalent of that digit:

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