02 Primitive data types and variables

Primitive Data
Types andVariables
Creating and RunningYour First C# Program
Svetlin Nakov
Telerik Corporation
www.telerik.com

Table of Contents
1. Primitive DataTypes
 Integer
 Floating-Point / Decimal Floating-Point
 Boolean
 Character
 String
 Object
2. Declaring and UsingVariables
 Identifiers
 DeclaringVariables and AssigningValues
 Literals
3. Nullable types
2

How Computing Works?
Computers are machines that process data
 Data is stored in the computer memory in
variables
 Variables have name, data type and value
Example of variable definition and assignment
in C#
int count = 5;
Data type
Variable name
Variable value
4

What Is a DataType?
A data type:
Is a domain of values of similar characteristics
Defines the type of information stored in the
computer memory (in a variable)
Examples:
Positive integers: 1, 2, 3, …
Alphabetical characters: a, b, c, …
Days of week: Monday, Tuesday, …
5

DataType Characteristics
A data type has:
Name (C# keyword or .NET type)
Size (how much memory is used)
Default value
Example:
Integer numbers in C#
Name: int
Size: 32 bits (4 bytes)
Default value: 0
6

What are IntegerTypes?
Integer types:
Represent whole numbers
May be signed or unsigned
Have range of values, depending on the size of
memory used
The default value of integer types is:
0 – for integer types, except
0L – for the long type
8

IntegerTypes
Integer types are:
sbyte (-128 to 127): signed 8-bit
byte (0 to 255): unsigned 8-bit
short (-32,768 to 32,767): signed 16-bit
ushort (0 to 65,535): unsigned 16-bit
int (-2,147,483,648 to 2,147,483,647): signed
32-bit
uint (0 to 4,294,967,295): unsigned 32-bit
9

IntegerTypes (2)
More integer types:
long (-9,223,372,036,854,775,808 to
9,223,372,036,854,775,807): signed 64-bit
ulong (0 to 18,446,744,073,709,551,615):
unsigned 64-bit
10

MeasuringTime – Example
Depending on the unit of measure we may use
different data types:
byte centuries = 20; // Usually a small number
ushort years = 2000;
uint days = 730480;
ulong hours = 17531520; // May be a very big number
Console.WriteLine("{0} centuries is {1} years, or {2}
days, or {3} hours.", centuries, years, days, hours);
11

Floating-Point and Decimal
Floating-PointTypes

What are Floating-PointTypes?
Floating-point types:
Represent real numbers
May be signed or unsigned
Have range of values and different precision
depending on the used memory
Can behave abnormally in the calculations
14

Floating-Point Types
Floating-point types are:
float (±1.5 × 10−45 to ±3.4 × 1038): 32-bits,
precision of 7 digits
double (±5.0 × 10−324 to ±1.7 × 10308): 64-bits,
precision of 15-16 digits
The default value of floating-point types:
Is 0.0F for the float type
Is 0.0D for the double type
15

PI Precision – Example
See below the difference in precision when using
float and double:
NOTE:The “f” suffix in the first statement!
 Real numbers are by default interpreted as double!
 One should explicitly convert them to float
float floatPI = 3.141592653589793238f;
double doublePI = 3.141592653589793238;
Console.WriteLine("Float PI is: {0}", floatPI);
Console.WriteLine("Double PI is: {0}", doublePI);
16

Abnormalities in the
Floating-Point Calculations
Sometimes abnormalities can be observed
when using floating-point numbers
Comparing floating-point numbers can not be
performed directly with the == operator
Example:
double a = 1.0f;
double b = 0.33f;
double sum = 1.33f;
bool equal = (a+b == sum); // False!!!
Console.WriteLine("a+b={0} sum={1} equal={2}",
a+b, sum, equal);
17

Decimal Floating-PointTypes
There is a special decimal floating-point
real number type in C#:
decimal (±1,0 × 10-28 to ±7,9 × 1028): 128-bits,
precision of 28-29 digits
Used for financial calculations
No round-off errors
Almost no loss of precision
The default value of decimal type is:
0.0M (M is the suffix for decimal numbers)
18

Floating-Point and Decimal
Floating-PointTypes
Live Demo

The Boolean DataType
The Boolean data type:
Is declared by the bool keyword
Has two possible values: true and false
Is useful in logical expressions
The default value is false
21

BooleanValues – Example
Example of boolean variables taking values of
true or false:
int a = 1;
int b = 2;
bool greaterAB = (a > b);
Console.WriteLine(greaterAB); // False
bool equalA1 = (a == 1);
Console.WriteLine(equalA1); // True
22

The Character DataType
The character data type:
Represents symbolic information
Is declared by the char keyword
Gives each symbol a corresponding integer code
Has a '0' default value
Takes 16 bits of memory (from U+0000 to
U+FFFF)
25

Characters and Codes
The example below shows that every symbol
has an its unique Unicode code:
char symbol = 'a';
Console.WriteLine("The code of '{0}' is: {1}",
symbol, (int) symbol);
symbol = 'b';
symbol = 'A';
26

The String DataType
The string data type:
Represents a sequence of characters
Is declared by the string keyword
Has a default value null (no value)
Strings are enclosed in quotes:
Strings can be concatenated
Using the + operator
string s = "Microsoft .NET Framework";
29

Saying Hello – Example
Concatenating the two names of a person to
obtain his full name:
NOTE: a space is missing between the two
names!We have to add it manually
string firstName = "Ivan";
string lastName = "Ivanov";
Console.WriteLine("Hello, {0}!n", firstName);
string fullName = firstName + " " + lastName;
Console.WriteLine("Your full name is {0}.",
fullName);
30

The ObjectType
The object type:
Is declared by the object keyword
Is the base type of all other types
Can hold values of any type
33

Using Objects
Example of an object variable taking different
types of data:
object dataContainer = 5;
Console.Write("The value of dataContainer is: ");
Console.WriteLine(dataContainer);
dataContainer = "Five";
Console.Write("The value of dataContainer is: ");
Console.WriteLine(dataContainer);
34

What Is aVariable?
A variable is a:
Placeholder of information that can usually be
changed at run-time
Variables allow you to:
Store information
Retrieve the stored information
Manipulate the stored information
37

Variable Characteristics
A variable has:
Name
Type (of stored data)
Value
Example:
Name: counter
Type: int
Value: 5
int counter = 5;
38

DeclaringVariables
When declaring a variable we:
Specify its type
Specify its name (called identifier)
May give it an initial value
The syntax is the following:
Example:
<data_type> <identifier> [= <initialization>];
int height = 200;
40

Identifiers
Identifiers may consist of:
Letters (Unicode)
Digits [0-9]
Underscore "_"
Identifiers
Can begin only with a letter or an underscore
Cannot be a C# keyword
41

Identifiers (2)
Identifiers
Should have a descriptive name
It is recommended to use only Latin letters
Should be neither too long nor too short
Note:
In C# small letters are considered different than
the capital letters (case sensitivity)
42

Identifiers – Examples
Examples of correct identifiers:
Examples of incorrect identifiers:
int new; // new is a keyword
int 2Pac; // Cannot begin with a digit
int New = 2; // Here N is capital
int _2Pac; // This identifiers begins with _
string поздрав = "Hello"; // Unicode symbols used
// The following is more appropriate:
string greeting = "Hello";
int n = 100; // Undescriptive
int numberOfClients = 100; // Descriptive
// Overdescriptive identifier:
int numberOfPrivateClientOfTheFirm = 100;
43

AssigningValues
Assigning of values to variables
Is achieved by the = operator
The = operator has
Variable identifier on the left
Value of the corresponding data type on the
right
Could be used in a cascade calling, where
assigning is done from right to left
45

AssigningValues – Examples
Assigning values example:
int firstValue = 5;
int secondValue;
int thirdValue;
// Using an already declared variable:
secondValue = firstValue;
// The following cascade calling assigns
// 3 to firstValue and then firstValue
// to thirdValue, so both variables have
// the value 3 as a result:
thirdValue = firstValue = 3; // Avoid this!
46

Initializing Variables
Initializing
Is assigning of initial value
Must be done before the variable is used!
Several ways of initializing:
By using the new keyword
By using a literal expression
By referring to an already initialized variable
47

Initialization – Examples
Example of some initializations:
// The following would assign the default
// value of the int type to num:
int num = new int(); // num = 0
// This is how we use a literal expression:
float heightInMeters = 1.74f;
// Here we use an already initialized variable:
string greeting = "Hello World!";
string message = greeting;
48

Assigning and
InitializingVariables
Live Demo

What are Literals?
Literals are:
Representations of values in the source code
There are six types of literals
Boolean
Integer
Real
Character
String
The null literal
51

Boolean and Integer Literals
The boolean literals are:
true
false
The integer literals:
Are used for variables of type int, uint, long,
and ulong
Consist of digits
May have a sign (+,-)
May be in a hexadecimal format
52

Integer Literals
Examples of integer literals
The '0x' and '0X' prefixes mean a
hexadecimal value, e.g. 0xA8F1
The 'u' and 'U' suffixes mean a ulong or uint
type, e.g. 12345678U
The 'l' and 'L' suffixes mean a long or ulong
type, e.g. 9876543L
53

Integer Literals – Example
Note: the letter ‘l’ is easily confused with the
digit ‘1’ so it’s better to use ‘L’!!!
// The following variables are
// initialized with the same value:
int numberInHex = -0x10;
int numberInDec = -16;
// The following causes an error,
because 234u is of type uint
int unsignedInt = 234u;
// The following causes an error,
because 234L is of type long
int longInt = 234L;
54

Real Literals
The real literals:
Are used for values of type float, double and
decimal
May consist of digits, a sign and “.”
May be in exponential notation: 6.02e+23
The “f” and “F” suffixes mean float
The “d” and “D” suffixes mean double
The “m” and “M” suffixes mean decimal
The default interpretation is double
55

Real Literals – Example
Example of incorrect float literal:
A correct way to assign floating-point value
(using also the exponential format):
56
// The following causes an error
// because 12.5 is double by default
float realNumber = 12.5;
// The following is the correct
// way of assigning the value:
float realNumber = 12.5f;
// This is the same value in exponential format:
realNumber = 1.25e+7f;

Character Literals
The character literals:
Are used for values of the char type
Consist of two single quotes surrounding the
character value: '<value>'
The value may be:
Symbol
The code of the symbol
Escaping sequence
57

Escaping Sequences
Escaping sequences are:
Means of presenting a symbol that is usually
interpreted otherwise (like ')
Means of presenting system symbols (like the
new line symbol)
Common escaping sequences are:
 ' for single quote " for double quote
 for backslash n for new line
 uXXXX for denoting any other Unicode symbol
58

Character Literals – Example
Examples of different character literals:
char symbol = 'a'; // An ordinary symbol
symbol = 'u006F'; // Unicode symbol code in
// a hexadecimal format
symbol = 'u8449'; // 葉 (Leaf in Traditional Chinese)
symbol = '''; // Assigning the single quote symbol
symbol = ''; // Assigning the backslash symbol
symbol = 'n'; // Assigning new line symbol
symbol = 't'; // Assigning TAB symbol
symbol = "a"; // Incorrect: use single quotes
59

String Literals
String literals:
Are used for values of the string type
Consist of two double quotes surrounding the
value: "<value>"
May have a @ prefix which ignores the used
escaping sequences: @"<value>"
The value is a sequence of character literals
string s = "I am a sting literal";
60

String Literals – Example
Benefits of quoted strings (the @ prefix):
In quoted strings " is used instead of ""!
// Here is a string literal using escape sequences
string quotation = ""Hello, Jude", he said.";
string path = "C:WINNTDartsDarts.exe";
// Here is an example of the usage of @
quotation = @"""Hello, Jimmy!"", she answered.";
path = @"C:WINNTDartsDarts.exe";
string str = @"some
text";
61

NullableTypes
Nullable types are instances of the
System.Nullable struct
Wrapper over the primitive types
E.g. int?, double?, etc.
Nullabe type can represent the normal range
of values for its underlying value type, plus an
additional null value
Useful when dealing with Databases or other
structures that have default value null

NullableTypes – Example
int? someInteger = null;
Console.WriteLine(
"This is the integer with Null value -> " + someInteger);
someInteger = 5;
Console.WriteLine(
"This is the integer with value 5 -> " + someInteger);
double? someDouble = null;
Console.WriteLine(
"This is the real number with Null value -> "
+ someDouble);
someDouble = 2.5;
Console.WriteLine(
"This is the real number with value 5 -> " +
someDouble);
Example with Integer:
Example with Double:

Questions?
Primitive Data
Types andVariables
http://academy.telerik.com

Exercises
1. Declare five variables choosing for each of them the
most appropriate of the types byte, sbyte, short,
ushort, int, uint, long, ulong to represent the
following values: 52130, -115, 4825932, 97, -10000.
2. Which of the following values can be assigned to a
variable of type float and which to a variable of
type double: 34.567839023, 12.345, 8923.1234857,
3456.091?
3. Write a program that safely compares floating-point
numbers with precision of 0.000001.
68

Exercises (2)
4. Declare an integer variable and assign it with the
value 254 in hexadecimal format. Use Windows
Calculator to find its hexadecimal representation.
5. Declare a character variable and assign it with the
symbol that has Unicode code 72. Hint: first use the
Windows Calculator to find the hexadecimal
representation of 72.
6. Declare a boolean variable called isFemale and
assign an appropriate value corresponding to your
gender.
69

Exercises (3)
7. Declare two string variables and assign them with
“Hello” and “World”. Declare an object variable and
assign it with the concatenation of the first two
variables (mind adding an interval). Declare a third
string variable and initialize it with the value of the
object variable (you should perform type casting).
8. Declare two string variables and assign them with
following value:
Do the above in two different ways: with and
without using quoted strings.
The "use" of quotations causes difficulties.
70

Exercises (4)
9. Write a program that prints an isosceles triangle of
9 copyright symbols ©. Use Windows Character
Map to find the Unicode code of the © symbol.
10. A marketing firm wants to keep record of its
employees. Each record would have the following
characteristics – first name, family name, age,
gender (m or f), ID number, unique employee
number (27560000 to 27569999). Declare the
variables needed to keep the information for a
single employee using appropriate data types and
descriptive names.
11. Declare two integer variables and assign them with
5 and 10 and after that exchange their values.
71

02 Primitive data types and variables

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