CS4443
MODERN PROGRAMMING LANGUAGE – I
Mr. Dilawar
Lecturer,
Computer Science Faculty,
Bakhtar University
Kabul, Afghanistan.

Previous Outline
• The C# language
• The .NET Architecture and .NET Framework
• CLR, MSIL, JITers, FCL, CLS, CTS and GC
• C# compare to C++
• Development Environment
• Console Applications and Windows Form Application
• Working with First Hello World Program in C#
• Understanding namespaces, using keyword, class keyword, main() method
and comments in C#

C# Language Fundamentals
Chapter 2

Chapter Outline
• Basic Data Types and their Mapping to CTS
• Variables, Constants, and Operators
• Working with Flow Control and Conditional Statements
• Type Conversion, String Manipulation and Complex Variable Types
• Arrays in C#
• Foreach loop

Lecture Outline
• Basic Data Types and their Mapping to CTS
• Variables, Constants, and Operators
• Working with Flow Control and Conditional Statements
• Type Conversion, String Manipulation and Complex Variable Types
• Arrays in C#
• Foreach loop

Basic Data Types and their Mapping to CTS
• Data types are implemented based on their classification.
• Value types (implicit data types, structures, and enumeration)
• Reference types (objects, strings, arrays, delegates)
• A data type is a value type if it holds the data within its own memory
allocation.
• A variable of a value type is passed to method by passing an exact copy.
• A reference type contains a pointer to another memory location that holds
the data.
• A variable of a reference type is passed to method by passing only their reference.

Basic Data Types and their Mapping to CTS
• Implicit data types are defined by the language vender.
• Explicit data types are composed or made by using the implicit data
type.
• Implicit data types are complaint with .NET complaint languages and
are mapped to types in the CTS.
• Hence each implicit data type in C# has its corresponding .NET type.
• The implicit data types in C# are given in the next slide.

Basic Data Types and their Mapping to CTS
C# Type .NET Type Size in Bytes Description
byte Byte 1 May contain integers from 0 – 255
sbyte Sbyte 1 Signed byte from -128 to 127
short Int16 2 Ranges from -32768 to +32767
ushort UInt16 2 Unsigned, ranges from 0 to 65535
int Int32 4 Ranges from -2147483648 to +2147483647
uint UInt32 4 Unsigned, ranges from 0 to 4294967295
long Int64 8 -9223372036854775808 to
+9223372036854775808
ulong UInt64 8 Unsigned, ranges from 0 to
18446744073709551615

Basic Data Types and their Mapping to CTS
C# Type .NET Type Size in Bytes Description
float Single 4 Ranges from ±1.5 × 10
− 45 to ±3.4 × 10
− 38
precision. Requires the suffix f ot F.
double Double 8 Ranges from ±5.0 × 10
− 324 to ±1.7 × 10308
with 15-16 digits precision.
bool Boolean 1 Contains either true or false
char Char 2 Contains any single Unicode character enclosed in
single quotation mark such as ‘c’
decimal Decimal 12 Ranges from 1.0 × 10
− 28 to 7.9 × 1028 with 28-
29 digits precision. Requires the suffix ‘m’ or ‘M’

Basic Data Types and their Mapping to CTS
• Implicit data types are represented in language using keywords in C#.
• string is also a keyword in C#.
• Implicit data types – are value types and they are stored on stack.
• A stack is a data structure that store items in FIFO fashion.
• It is an area of memory supported by the processor and its size is determined at the
compile time.
• While user defined types or referenced types are stored using heap.
• A heap consists of memory available to the program at runtime.
• Reference types are allocated using memory available from the heap dynamically.

Variables
• A variable is the name given to a memory location holding a particular
type of data.
• Each variable has a data type and a value.
• In C#, variable are declared as:
<data type> <variable_name>;
• You can initialize the variable as you declare it (on the fly).
• You can also declare/initialize multiple variables of the same type in a single
statement.

Variables
• In C#, like other languages you must declare variables before using
them.
• Definite Assignment – Local variables must be initialized before being
used.
• C# does not assign default values to local variables.
• C# is also a type safe language.
• Values of particular data type can only be stored in their respective data type.
• Can’t store integer values in Boolean data types like we do in C/C++.

Naming Conventions for Variable and
Methods
• Microsoft suggests using Carrel Notation for variables.
• First letter in lowercase.
• Pascal Notation for methods.
• First letter in uppercase.
• Each word after the first word in the name of both variables and
methods should start with a capital letter.

Constants
• Constants are variables whose values, once defined, can not be
changed by the program.
• Constant variables are declared using the CONST keyword like:
const double PI = 3.142;
• Constant variables must be initialized as they are declared.
• It is conventional to use capital letters when naming constant
variables.

Operators
• Symbols used to perform operation on the data.
• Arithmetic operators +, -, *, /, %
• Increment and Decrement ++, --
• Prefix and Postfix notation
• In prefix, the compiler will increment the variable and then will use it.
• In postfix, the compiler will first use and then increment it.
• Arithmetic Assignment Operators S+=, -=, *=, /=, %=
• Relational Operators ==, !=, >, <, >=, <=
• Logical and Bitwise Operators &, |, ^, !, &&, ||
• Other operators <<, >>, ., [], (), ? :

Expressions
• C# contains number of operators for this purpose.
• By combining operators with variables and literal value (together referred as
operands), you can create expressions, which is the building blocks of
computation.

Operator Precedence

Flow Control and Conditional Statements
The if Statement

Flow Control and Conditional Statements
The if…….else….. Statement
Nested if and Nested if-else

Flow Control and Conditional Statements
The switch……..case Statement

Flow Control and Conditional Statements
The for loop Statement
Use of Continue
and Break
Statement.

Flow Control and Conditional Statements
The do……while Loop Statement

Flow Control and Conditional Statements
The while Loop Statement

Flow Control and Conditional Statements
The goto Statement

Type Conversion
• There are two types of type conversion:
• Implicit and Explicit conversion
• Implicit conversion requires no work on your part and no additional
code.

Type Conversion

Type Conversion
• As the name suggests, an explicit conversion occurs when you
explicitly ask the compiler to convert a value from one data type to
another.
• Requires extra code, and format of this code may vary, depending on the
exact conversion method.

Type Conversion
• Before working with explicit conversion, try the code below:

Type Conversion
• To get the code compile, you need to add some code.
• in this context, you have to cast the short variable into a byte (as suggested by
the preceding error string).
• Casting basically means forcing data from one type into another, and
it uses the following simple syntax:
<(destinationType)sourceVar>

Type Conversion

Type Conversion

Type Conversion
• Attempting to fit a value into a variable when that value is too big for
the type of that variable results in an overflow, and this is the
situation you want to check for.
• Two keywords exist for setting what is called the overflow checking
context for an expression: checked and unchecked.
checked (<expressions>)
unchecked (<expressions>)

Type Conversion

Type Conversion
• You can also use
Convert command to
make explicit conversion.

String Manipulation
• Writing strings to console, reading strings from the console, and
concatenating strings using the + operator.
• A string type variable can be treated as a read-only array of char
variables.
• You can access individual characters using syntax like the following:

String Manipulation
• To get a char array you have to use ToCharArray() command of
the array variable.
• Later, you can manipulate it as normal array of characters.
• You can access the number of elements using myString.Length.

String Manipulation
• You can work with other operations like <string.ToUpper()>
and <string.ToLower()> and etc…
• As it not changes the original value so it’s better to assign it into
another variable again.

String Manipulation
• For removing extra spaces for ease of
interpretation so you can use
<string>.Trim() command.
• You can also specify which string to trim from
the string.
• You can work <string>.TrimStart()
and <string>.TrimEnd()
• Spaces from the beginning and end of the string.
• You can use <string>.PadLeft() and
<string>.PadRight().

Complex Variable Types
• Enumeration (often referred to as enum), structs (referred to as
structures) and arrays.
• Enumeration allow the definition of a type that can take one of a
finite set of values that you supply.
• Orientation example – creating enum type called orientation.
• It creates a user-defined type and then it is applied to a variable.

Complex Variable Types
• You can use enum keyword to define
enumeration as given.
• Next, you can declare variable of this
new type.
• You can assign values using the given
syntax.

Complex Variable Types
• structs are data structures
that are composed of several
pieces of data, possibly of
different types.
• You can use struct keyword to
define structure as given.

Arrays
• Situations where you want to store a lot of data, so you have to
declare individual variables as
• Arrays are indexed lists of variables stored in a single array type
variable.
• An array called friendNames that stores the three names (elements) and can
be accessed through number (index) in square brackets, as shown:

Arrays
• Arrays are declared in the following way:
• Arrays can be initialized in two ways:

Arrays
• Alternative ways

foreach Loop
• A foreach loop enables you to address each element in an array
using this simple syntax:
• This loop will cycle through each element, placing it in the variable
<name> in turn, without danger of accessing illegal elements.
• It gives you read-only access to the array contents.

foreach Loop

Summery
• Basic Data Types and their Mapping to CTS
• Variables, Constants, and Operators
• Working with Flow Control and Conditional Statements
• Type Conversion, String Manipulation and Complex Variable Types
• Arrays in C#
• foreach loop

Thank You
For your Patience