Number System and Codes

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Number System and Codes
Chapter 3 Number System and Codes

Decimal and Binary Numbers

Decimal and Binary Numbers

Converting Decimal to Binary
Sum of powers of 2

Converting Decimal to Binary
Repeated Division

Binary Numbers and Computers

Representing Integers with binary
Some of challenges:- Integers can be positive or negative Each integer should have a unique representation The addition and subtraction should be efficient.

Representing a positive numbers

Representing a negative numbers using Sign-Magnitude notation
-5 = bits sign-manitude -55= bits sign-magnitude

1’s Complement The 1’s complement representation of the positive number is the same as sign-magnitude. +84 =

1’s Complement The 1’s complement representation of the negative number uses the following rule:- Subtract the magnitude from 2n-1 For example: -36 = ??? +36 =

1’s Complement Example :- - 57 +57 = -57 =

Converting to decimal format

2’s Complement For negative numbers:-
Subtract the magnitude from 2n. Or Add 1 to the 1’s complement

Example

Convert to decimal value
Positive values:- = +89 Negative values

Two's Complement Arithmetic

Adding Positive Integers in 2's Complement Form

Adding Positive and Negative Integers in 2's Complement Form

Adding Positive and Negative Integers in 2's Complement Form

Subtraction of Positive and Negative Integers

Digital Codes Binary Coded Decimal (BCD)

BCD

BCD

4221 Code

Gray Code In pure binary coding or 8421 BCD then counting from 7 (0111) to 8 (1000) requires 4 bits to be changed simultaneously. Gray coding avoids this since only one bit changes between subsequent numbers

Binary –to-Gray Code Conversion

Gray –to-Binary Conversion

Gray –to-Binary Conversion

The Excess-3- Code

Parity The method of parity is widely used as a method of error detection. Extar bit known as parity is added to data word The new data word is then transmitted. Two systems are used: Even parity: the number of 1’s must be even. Odd parity: the number of 1’s must be odd.

Parity Example: Odd parity Even Parity 110010 110011 11001 111101
111100 11110 110001 110000 11000