1. Computer Code

2. Introduction The Language of electronic component is binary
All numeric and non-numeric data must be converted into binary language so that computer can understand it
Representation of all numeric and non-numeric data in binary digits is known as computer code
Computer code is represented in different coding schemes

3. Coding Schemes
BCD Code
ASCII Code
EBCDIC Code
Unicode

4. BCD Code Stands for Binary Coded Decimal
Used to represent decimal digits in binary
4-bit code
Each decimal digit is represented by 4 binary digits
Used by early computers

5. BCD Code

6. Example

7. Example

8. ASCII Code American Standard Code for Information Interchange
Most widely used coding scheme for personal computers
7-bit code can represent 128 characters
Not enough to represent some graphical characters displayed on computer screens
An 8 bit code can represent 256 characters
Extended 128 unique codes represent graphic symbols

9. ASCII Code

10. Example Character Decimal Code Binary Code B 66 01000010 i 105 n
110 a 97 r
114 y
121

11. EBCDIC Code Extended Binary Coded Decimal Interchange Code 8-bit code
Divided into two group of 4 bits
Each group cam represent one hexadecimal digit
Normally used in mainframe computers
Can represent 256 characters

12. EBCDIC Code

13. Unicode 16 bit code Represent 65536 characters
Started to replace ASCII code
Can represent the characters of all languages in the world

14. Boolean Algebra Algebra of logic
Also called logical algebra or switching algebra
Uses symbols to represent logical statements instead of words
Consists of different rules to manipulate rules
Similar to calculus

15. Boolean Algebra Used in the designing of logic circuits in computer
Computer chips consists of transistors that are arranged in logical gates
Each gate performs a single logical operation
Computer performs logical operation by processing electrical pulses
Design of a particular circuit is based on a set of logical statements
Results of boolean algebra can be true or false
The digit 1 indicates true and 0 indicates false result

16. Elements of Boolean Algebra
An expression in Boolean Algebra can be formed using different elements of Boolean algebra
Different elements of Boolean algebra are as follows:
Boolean Variables
Boolean Constants
Logical Operators
Parentheses

17. Logical Operators in Boolean Algebra
Symbols used to perform logical operations are called logical operators
Different logical operators are:
AND OR
NOT

18. Basic Logic Gates
Many basic functions of the arithmetic and control units are carried out by logic gates
Each gate accepts input and produces an output
NOT Gate
AND Gate
OR Gate
NAND Gate
NOR Gate
XOR Gate
XNOR Gate

19. Boolean Expression Logical statement that is either true or false
Consists of different elements of Boolean Algebra

20. Logic Diagrams and Expressions
Logic Equation Z Y X F + =
Truth Table 1
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
X Y Z Z Y X F × + = X Y F Z
Logic Diagram
Boolean equations, truth tables and logic diagrams describe the same function!
Truth tables are unique, but expressions and logic diagrams are not. This gives flexibility in implementing functions.

21. Boolean Algebra X + 0 = + 1 X + X X = X X = . 0 X . X
Invented by George Boole in 1854
An algebraic structure defined by a set B = {0, 1}, together with two binary operators (+ and ·) and a unary operator ( )
Identity element 1. 3. 5. 7. 9. X
+ 0 = + 1
X + X
X = X 2. 4. 6. 8. X
. 1 =
. 0
X . X
Idempotence
Complement
Involution
10.
12.
14.
16.
X + Y
Y + X =
(X + Y) Z +
X + (Y Z)
X(Y + XY XZ
X . Y
11.
13.
15.
17. XY YX =
(XY) Z
X(Y Z) X
+ YZ
(X + Y)
(X + Z)
X . Y
X + Y
Commutative
Associative
Distributive
DeMorgan ’ s

22. References
Slides Taken From: pt
Introduction to Information Technology by Riaz Shahid, CM Aslam and Safia Iftikhar
The Concepts of Information Technology by Imran Saeed, Ahsan Raza, Tariq Mehmood and Zafar Hussain