Values

1
Values Variables
2
Properties of variables

• Should have a type
• Stores data
• Case sensitive
• Their names can not start with a number
• Reserved keywords can not be used as variable
  names

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Keywords
4
How to define a variable
Type
Value

• int x 3

Variable
Semicolon End of statement
5
Ways to define a variable

• int nInteger
• string sString

int nInteger 42 string sString "This is a
string!"
int nInteger string sString ... nInteger
42 sString "This is a string!"
Double quotes represents a string
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Necessity to set a value to a variable

• string sValueless
• MessageBox.Show(sValueless)
• Error!

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Variable Types

• Simple types
• Integers
• Floating point numbers
• Characters
• Strings

8
Integers

• short 2 bytes (32,768 lt-gt 32,767)
• short sval -12
• ushort 2 bytes (0 lt-gt 65,535)
• ushort sval 12
• int 4 bytes (2,147,483,647 lt-gt 2,147,483,647)
• int nval -12500
• uint 4 bytes (0 lt-gt 4,294,967,295)
• uint nval 12500
• long 8 bytes
• long lVal -548444101
• ulong 8 bytes
• Ulong lVal 548444101

9
Floating Point Numbers

• float 4 bytes
• float fVal -1,2
• double 8 bytes
• double dVal -3.565
• decimal 8 bytes
• decimal dVal -3456.343

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Expressions

• Expressions are used for performing operations
  over variables.
• Return a value of known type.
• Two types of expressions
• Operators
• Functions

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Arithmetic operations

• They need more than one variable.
• Performs mathematical operations
• (addition operation)
• - (subtraction operation)
• (multiplication operation)
• / (division operation)
• (modulus operation)
• .

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Arithmetic operations

• Abbreviations
• int m 5
• int n 4
• m m n equals m n
• In other words in the end of both expressions
  m will have value of 9 and the value of n will
  not be changed.

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Increment and decrement operations

• They operate on one variable
• is increment operator
• i i i 1
• -- is decrement operator
• i -- i i 1
• Prefix and postfix operators will yield to
  different results.
• i.e. i and i are not same.

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Increment and decrement operations

• k The result of the operation is the value of
  the operand after it has been incremented.
• k The result of the operation is the value of
  the operand before it has been incremented.
• --k The result of the operation is the value
  of the operand after it has been decremented.
• k-- The result of the operation is the value
  of the operand before it has been decremented.

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Example
int k0, m m k
Values of m and k will be 1
int k0, m m k
m will be 0 and k will be 1
int k5, m, n2 m --k n
m will be 6 and k will be 4
int k0, m, n7 m k --n
m will be 6 and k will be 1 and n will be 6
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Exercise

• What will be the values of the variables after
  code piece below is executed?

int i, j, k i 2 j 3 i k 3 i
i k j-- i / k-- j
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Exercise

• Assuming that line of codes are independent, what
  will be the value of variable m after each line
  is executed?

• int i 0, j 6, k 4 , m 5
• m k-- i
• m j 4
• m k (j-- i)

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Order of Operations

• Rules that defines which procedures should be
  performed first.
• In C language some operators have execution
  privilege over others.
• To predict the result of an expression first we
  should know the order of operations.

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Example

• PEMDAS phrase may help to remember the order.

P Parenthesis E Exponent M Multiplication D D
ivision A Addition S Subtraction
1 2 3 - 4 / 5 ?
1 (2 3) (4 / 5)
6.2
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Example(result)

• If we use all numbers in integer type then the
  result will be integer(In other words fraction
  will be removed)

1 (2 3) (4 / 5)
4/5 0 (integer division)
7
21
Exercise

• Different data types may yield different results
  in same operations.
• Write and execute the codes in the next slides.
• Explain the difference between results.

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Exercise (continues)
23
Exercise (continues)
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Characters

• char 1 byte 0-256

'a' 'z' 'A' 'Z' '?' '_at_' '0' '9'
Special characters are represented by using \
prefix. '\n' new line '\t' tab '\''
single quote '\\' backslash
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Strings (Character Arrays)

• Sequence of characters.
• Example
• Hello!
• first line\n second line \n third line
• Empty string

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Strings

• string Class
• Unicode 16 bit
• Example
• string myString Hello!
• Verbatim strings
• string myString _at_2.5 disk

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string operations

• Appending two strings

Result Hello world!
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string operations

• Searching within a string
• int IndexOf ()

Result 1
Exercise Find the usage of LastIndexOf()
function and write an example by using this
function.
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string operations

• Retrieve a substring from a string
• string Substring()

Result llo
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Exercise

• Put your name and surname into two string
  variables.
• Concatenate two strings.
• Write the result to the console.

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DateTime

• C language has built-in DateTime structure to
  represent date and time values.
• We can store year, month, day, hour, minute,
  second values in a DateTime structure.

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Creating a DateTime Object

• DateTime dt new DateTime(year, month, day)

Creating a new object
Type
Variable name
Initial values
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DateTime Fundamentals

• Functions and Properties
• AddDays, AddMonths, AddYears
• DateTime.Now
• DayOfWeek
• TimeSpan

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Example
A new DateTime object is created
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Constants

• Their values can not be changed.
• They have types.
• We can use them in expressions bur can not alter
  them.
• Defined by using const keyword before variable
  type.
• Their values can be set only during definition
  line.
• const int nVar 34

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Example