This document discusses data types in C# programming. It covers increment and decrement operators, assignment operators, basic data types like integers, floats and booleans. It also discusses constants, conditional logical operators like AND, OR and NOT. Examples are provided to demonstrate how to use these operators and data types in C# code. The objectives are to learn about these fundamental programming concepts in C#.

1. Data Types
Lecture 2
Dr. Hakem Beitollahi
Computer Engineering Department
Soran University

2. Objectives of this lecture
 In this chapter you will learn:
 Increment and Decrement (++ and --)
 Assignment Operators
 Basic data types in C#
 Constant values
 Conditional logical operators
Data Types— 2

3. Main Mathematic Operations
Operator Action
+ Addition
- Subtraction
* Multiply
/ Division
% Reminder
++ Increment
-- Decrement
Data Types— 3

4. Increment & decrement (I)
 C/C++/C# includes two useful operators not found in some other
computer languages.
 These are the increment and decrement operators, ++ and - -
 The operator ++ adds 1 to its operand, and − − subtracts 1.
 i++ = i + 1
 i-- = i - 1
 Both the increment and decrement operators may either precede
(prefix) or follow (postfix) the operand
 i = i+1 can be written as i++ or ++i
 i = i -1 can be written as i-- or --i
 Please note: There is, however, a difference between the prefix and
postfix forms when you use these operators in an expression
Data Types— 4

5. Increment & decrement (II)
// Increment and Decrement Operations ++/--
using System;
class Comparison
{
static void Main( string[] args )
{
int a = 10;
int b = 10;
int x, y;
x = a++;
y = ++b;
Console.WriteLine("x = {0}, a ={1}.", x, a);
Console.WriteLine("y = {0}, b ={1}.", y, b);
}// end method Main
} // end class Comparison
x = 10 a = 11
y = 11 b = 11
Data Types— 5

6. Increment & decrement (III)
// Increment and Decrement Operations ++/--
using System;
class Comparison
{
static void Main( string[] args )
{
int a = 10;
int b = 10;
Console.WriteLine(a++);
Console.WriteLine(a);
Console.WriteLine(++b);
Console.WriteLine(b);
}// end method Main
} // end class Comparison
10
11
11
11
Data Types— 6

7. Common Programming Error 1
Attempting to use the increment or
decrement operator on an expression
other than a variable reference is a syntax
error. A variable reference is a variable or
expression that can appear on the left side
of an assignment operation. For example,
writing ++(x + 1) is a syntax error,
because (x + 1) is not a variable
reference
Data Types — 7

8. Assignment Operator
Data Types — 8

9. Assignment Operator (I)
 C# provides several assignment operators for
abbreviating assignment expressions.
 Example:
 c = c + 3;
 c += 3;
 where operator is one of the binary operators +,
-, *, / or %, can be written in the form
 variable operator= expression;
Data Types — 9

10. Assignment Operator (II)
Data Types — 10

11. Common Programming Error 1
Placing a space character between symbols
that compose an arithmetic assignment
operator is a syntax error.
A += 6; True A + = 6; False
Data Types — 11

12. Basic Data Types in C#
Data Types— 12

13. Basic data types in C# (I)
 Programming languages store and
process data in various ways depending
on the type of the data; consequently, all
data read, processed, or written by a
program must have a type
 A data type is used to
 Identify the type of a variable when the
variable is declared
 Identify the type of the return value of a
function (later)
 Identify the type of a parameter expected by
a function (later)
Data Types— 13

14. Basic data types in C# (II)
 There are 7 major data types in C++
 char e.g., ‘a’, ‘c’, ‘@’
 string e.g., “Zagros”
 int e.g., 23, -12, 5, 0, 145678
 float e.g., 54.65, -0.004, 65
 double e.g., 54.65, -0.004, 65
 bool only true and false
 void no value
Data Types— 14

15. Basic data types in C# (III)
Type Range Size (bits)
char U+0000 to U+ffff Unicode 16-bit character
sbyte -128 to 127 Signed 8-bit integer
byte 0 to 255 Unsigned 8-bit integer
short -32,768 to 32,767 Signed 16-bit integer
ushort 0 to 65535 Unsigned 16-bit integer
int -2,147,483,648 to 2,147,483,647 Signed 32-bit integer
uint 0 to 4,294,967,295 Unsigned 32-bit integer
long -9,223,372,036,854,775,808 to
9,223,372,036,854,775,807
Signed 64-bit integer
ulong 0 to 18,446,744,073,709,551,615 Unsigned 64-bit integer
float -3.402823e38 .. 3.402823e38 Signed 32 bits
double -1.79769313486232e308 ..
1.79769313486232e308
Signed 64 bits
decimal -79228162514264337593543950335 ..
79228162514264337593543950335
Signed 128 bits
Data Types— 15

16. Basic data types in C# (IV)
 The general form of a declaration is
 Type variable-list
 Examples
 int I, j, k;
 char ch, a;
 float f, balance;
 double d;
 bool decision;
 string str;
 Variables name
Correct incorrect
Count 3count
test23 hi!there
high_balance high...balance
_name Test?
@count co@nt
 The first character must be a letter
 -an underscore or @
 The subsequent characters must be either letters, digits, or
underscores
Data Types— 16

17. Constants in C#
Data Types— 17

18. Const variables (I)
 Variables of type const may not be changed by your
program
 The compiler is free to place variables of this type into
read-only memory (ROM).
 Example:
 const int a = 10;
Data Types— 18

19. // Constant learning
using System;
class Constant
{
static void Main( string[] args )
{
const int c = 999;
// c = 82; Error becuase c is constant and you cannot change it
// c = 999; Error becuase c is constant and you cannot change it
Console.WriteLine(c);
}// end method Main
} // end class Constant
Data Types— 19

20. Conditional Logical operators
Data Types— 20

21. Conditional Logical operators (I)
 Conditional logical operators are useful when we want to
test multiple conditions.
 There are 3 types of conditional logical operators and
they work the same way as the boolean AND, OR and
NOT operators.
 && - Logical AND
 All the conditions must be true for the whole
expression to be true.
 Example: if (a == 10 && b == 9 && d == 1)
means the if statement is only true when a == 10 and
b == 9 and d == 1.
Data Types— 21

22. expression1 expression2 expression1 && expression2
false false false
false true false
true false false
true true true
Data Types— 22

23. Conditional Logical operators (II)
 || - Conditional logical OR
 The truth of one condition is enough to make
the whole expression true.
 Example: if (a == 10 || b == 9 || d == 1)
means the if statement is true when either
one of a, b or d has the right value.
 ! – Conditional logical NOT (also called
logical negation)
 Reverse the meaning of a condition
 Example: if (!(points > 90))
means if points not bigger than 90.
Data Types— 23

24. expression1 expression2 expression1 || expression2
false false false
false true true
true false true
true true true
Expression !expression
false true
true false
Data Types— 24

25. Data Types — 25
// Conditional logical operator
using System;
class Conditional_logical
{
static void Main( string[] args )
{
int a = 10;
int b = 15;
if ((a == 10) && (b == 15))
Console.WriteLine("Apple");
else
Console.WriteLine("Orange");
if ((a == 10) || (b == 15))
Console.WriteLine("Apple");
else
Console.WriteLine("Orange");
if (!(a > 20))
Console.WriteLine("Apple");
else
Console.WriteLine("Orange");
}// end method Main
} // end class
Apple
Apple
Apple

26. Operator preferences
Operators Preferences
() 1
!,~,--,++ 2
*,/,% 3
+, - 4
<, <=, >=, > 5
==, != 6
&& 7
|| 8
Note: in a+++a*a, the * has preference over ++
Note: in ++a+a*a, the ++ has preference over *
Data Types— 26

27. Common Programming Error Tip
Although 3 < x < 7 is a mathematically correct
condition, it does not evaluate as you might expect in
C#. Use ( 3 < x && x < 7 ) to get the proper
evaluation in C#.
Using operator == for assignment and using operator =
for equality are logic errors.
Use your text editor to search for all occurrences of = in
your program and check that you have the correct
assignment operator or logical operator in each place.
Data Types— 27