Tribhuvan University

INSTUTE OF SCIENCE AND TECHNOLOGY(IOST)

Bachelor in Computer Science and Information Technology (B.SC CSIT)
VI Semester
NET Centric Computing(CSC-367 )
Unit-1.2: Basic Language Constructs

Instructor
Tekendra Nath Yogi
Tekendranath@gmail.com
 Contents: Basic Languages constructs
• An Overview of C#: Introduction, First Simple Program in C#, Basic
structure of C# Program.

• Tokens and data types in C#: Keywords, Data Types, Identifiers: Variables,
Literals

• Operators in C#: Types of Operators, Expressions, Operator precedence and

associativity.

• Control Statements: Conditional Statements: If, else, switch. Loop

Statements: while, for, do while loop and foreach loop, Jump Statements:
Break, continue, return, goto and throw statements.

• Console I/O in C# Program.

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 Introduction
• C# (pronounced as "C-Sharp“) is a simple, modern, general-purpose,
object-oriented programming language developed by Microsoft within its
.NET initiative led by Anders Hejlsberg. C# was first released in 2002.

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 Contd…,
• C# is mainly influenced by C, C++ and Java.

Figure: C# Family Tree.

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 C# Features
• Simple, Modern and General Purpose.

• Objected-Oriented and Component Oriented: Encapsulation, Inheritance,

abstraction and Polymorphism.

• Portable, Platform Independence, architecture neutral and Cross-language

interoperability.

• Type safe, strongly typed, Case Sensitive, secure, Robust and Scalable.

• Automatic Memory Management: Automatic garbage collection.

• Language Integrated Query (LINQ) support

• Asynchronous Programming by using async/await.

• Rich Standard Library.

• Exception Handling.

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 Introduction
• It is used to develop variety of the applications:
– Window applications

– Web applications

– Web Service applications

– Database applications.

– Mobile applications

– Distributed applications

– AI, ML and IOT applications

– And much, much more!

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 C# First Program

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 General Structure of C# Program

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 General Structure of C# Program

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 Example Program 1

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 Example Program 2

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 Example Program 3

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 Example Program 4

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 Comments C#
• Comments:
– Single line Comments: //comment text goes here.

– Multi-line comment: /* comment text goes here and may span in multiple lines */

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 C# Keywords
• The C# Reserved Keywords

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 C# Keywords
• The C# Contextual Keywords

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 C# Data Types – Value Types

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 C# Data Types – Value Types
• For a value type, a variable holds an actual value, such as 3.1416 or 212. In C#
value types as shown in table below:

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 C# Data Types – Value Types
• Integers:

• Floating Point Types: float: size-32 bit and range- 1.5E-45 to 3.4E+38.
double: size-64 bit and range - 5E-324 to 1.7E+308

• Decimal Types: size-128 bit and range - 1E-28 to 7.9E+28

• Characters: size-16 bit and range - 0 to 65535.

• The bool Types: size- 1 bit, values: true and false.

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 C# Data Types – Reference Types
• For a reference type, a variable holds a reference to the value.

• E.g., object, class, string, etc.

• Declaration and assignment of reference type variable:

Class_name ref_var_name = new class_name( );

• E.g., ABC x = new ABC( );

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 C# Data Types – Dynamic Types
• Pointer: Pointer is a variable that hold the address of the another variable. It
uses & operator and * operator.

• Declaration of Pointer Variables: int *var;

• Initialization of Pointer variable: Let int x , then int *y =&x;

• Accessing value using pointer variable: *y

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 Identifiers in C# -- Literals
• Fixed value. For example, 110, ‘a’, “xyz”,etc.

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 Identifiers in C# -- Literals
Literal Example
Integer 100
Character ‘a’
Floating point 10.21f
Long int 12L
Unsigned int 100u
Unsigned long int 110ul
Double 10d
Decimal 10.5m
Hexadecimal 0x123a
String “xyz”
Verbatim string @”x
Y
z”

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 Identifiers in C# -- Literals
• Escape Sequences:

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 Identifiers in C# -- Variables
• Declaration: type var_name; . E.g., int x;

• Initialization: var_name = value; . E.g. x=10;

• Combining declaration and initialization: type var_name = value;. E.g., int

x=10;

• Declaring multiple variables of same type: int x, y, z;

• Declaring and initializing multiple variables of same type: int x=10, y=20,
z=30;

• Declaring and initializing multiple variables of same type with same value:
int x=y= z=100;

• Static initialization: z=100;

• Dynamic initialization: z= x + y;

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 Identifiers in C# -- Variables
• Implicitly typed variable: declared using keyword var and it must be
initialized by some value.

– Syntax: var var_name = value;

– E.g. var x=10;

• Note:
– Once that type has been determined, the variable has a type, and this type is fixed
throughout the lifetime of the variable.

– Only one implicitly typed variable can be declared at any one time.

– var s1 = 4.0, s2 = 5.0; // Error!

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 Type Conversion
• In a expression having mixed type of operands then need to convert the type
before applying the operation on the operands.

• Two types of Conversion:

– Implicit conversion: automatic type conversion, requires type compatibility, widening
conversion so no loss of information. E.g., float f; int i; f=i;

– Explicit Conversion: forced type conversion. Also known as type casting. Narrowing
conversion so, loss of information may occurs.

– Syntax: (target type)expression

– Example: double x, y; (int)(x/y);

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 Type Conversion

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 C# Operators
• Operator is a symbol that enables construction and evaluation of expressions in the
program.
• Operators in C#:
– Arithmetic Operator: +, -, *, /, %, ++, --
– Assignment operator: = and shorthand form of assignment operator.
– Relational Operator: <, >, <=, >=, ==, !=
– Logical Operator: &, |, ^, ||, &&, !
– Bitwise Operator: &, |, ^, ~, <<, >>
– Ternary Operator: Exp1? Exp2: Exp3;
– Array indexing Operator: [index]
– Member access Operator: ., ->
– Null Coalescing Operators: ??
– Type Testing and Casting Operators: is, as
– lambda operator: =>
– Await Operator: await
– Miscellaneous Operators: new, &, checked, unchecked, (cast), sizeof.

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 C# Operators: Arithmetic Operator

Operator Meaning Use (let A=10 , B= Result

3)
+ Addition A+B 13
- Subtraction A-B 7
* Multiplication A*B 30
/ Division A/B 3
% Modulus A%B 1
++ Increment A = ++B A= 4 and B=4
A=B++ A= 3 and B=4
-- Decrement A = --B A= 2 and B=2
A=B-- A= 3 and B=2

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 C# Operators: Relational Operator
Operator Meaning Use (let A=10 , B= Result
3)
< Less than A<B false
> Greater than A>B true
<= Less than or equal to A<=B false
>= Greater than or equal to A>=B true
== Equal to A==B false
!= Not equal to A != B true

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 Bitwise Operator: Logical Operator

Operator Meaning Use (let A=true , Result

B=false)
& AND A&B false
| OR A|B true
^ XOR A^B true
|| SHORT CIRCUIT OR A||B true
&& SHORT CIRCUIT AND A&&B false
! NOT !B true

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 Bitwise Operator: Bitwise Operator
• &, |, ^, ~, <<, >>

Operator Meaning Use (let A=1 1 0 1 0 Result

0 1 1 , B= 1 0 1 0 1
0 1 0)
& Bitwise-AND A&B 10000010
| Bitwise-OR A|B 11111011
^ Bitwise-XOR A^B 011111001
~ Bitwise-NOT ~B 01010101
<< Shift left A<<2 0 1 0 0 1 100
>> Shift right B>>2 001 0 1 0 1 0

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 Assignment operator:
• Var_name = expression;

• C# supports chain of assignment: x=y=z=10;

• Also includes compound assignment or shorthand assignment:

– var op=Expression.

– E.g. A+=B;

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 Ternary Operator (? :)
• Also known as conditional operator.

• Syntax: condition? Expression1: Expression 2.

• For example: if (a<b)? return true: return false.

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 Operator Precedence in C#

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 Operator Associativity in C#
• Operators having Right to left associativity:

– Ternary operator( ? :),

– unary operators (++, --, -, +, ~, !, sizeof, (type), * and &),

– equality relational operators(==, !=),

– assignment and shorthand assignment operator ( =, +=, …)

• Other, operators have left to right associativity.

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 Control Statements in C#
Statement that is used to change the normal sequential execution flow of a program.

if
Selection
Statements switch
while
do-while

Control Statements Iteration for

in C# Statements
foreach

break
continue
Jump
goto
Statements
return
throw
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Control Statements in C# -- selection Statement
• The if statement:
if(condition)

statement sequence

else

statement sequence

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 Contd…,

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Control Statements in C# -- selection Statement
• The Nested if statement:
if(condition)
{
if(condition)
{
statement sequence
}
else
{
statement sequence
}
}
else
{
statement sequence
}

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 Contd…,

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Control Statements in C# -- selection Statement
• The if-else-if Ladder:
if(condition){
statement;
}
else if(condition){
statement;
}
else if(condition){
statement;
}
...
else{
statement;
}

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 Contd…,

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Control Statements in C# -- selection Statement
• The Switch Statement:
switch(expression) {
case constant1:
statement sequence
break;
case constant2:
statement sequence
break;
case constant3:
statement sequence
break;
.
.
.
default:
statement sequence
break;
}
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 Contd…,

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Control Statements in C# -- Iteration Statement
• The For Loop:
for(initialization; condition; iteration)

statement sequence

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 Contd…,

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Control Statements in C# -- Iteration Statement
• The while Loop:
While(condition)

Statements

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 Contd…,

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Control Statements in C# -- Iteration Statement
• The do-while Loop:
do

statements;

} while(condition);

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 Contd…,

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Control Statements in C# -- Iteration Statement
• The foreach Loop:

– The foreach loop cycles through the elements of a collection such as array.

– The general form of foreach is:

foreach(type loopvar in collection) statement;

For example, foreach ( int x in Array_name) {statements;}

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 Contd…,

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 Control Statements in C# -- Jump Statement
• The break Statement: to exit a loop
Loop statement

{
If(condition)

break;

Statement after loop statement

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 Contd…,

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 Control Statements in C# -- Jump Statement
• The continue Statement: forces the next iteration of the loop to take place,
skipping any code in between.
Loop statement; can be for, while, do-while or foreach loop.

{
If(condition)

continue;

Statement after loop statement

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 Contd…,

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 Control Statements in C# -- Jump Statement
• The return Statement: causes a method to return. It can also be used to return
a value.
return_type method_name (args )

statements;

return x;

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 Contd…,

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 Control Statements in C# -- Jump Statement
• The goto statement:
Statement;

Label_name:

Statements;

if(condtion)

goto label_name;

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 Contd…,

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 Console I/O in C# Program
• Console.WriteLine(“ “);

• Var x = Console.ReadLine ( );

• y = int.parse(x);

• Now, y can be processed in a program as int data. Where as while reading it is

a string data.

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 Contd…,

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 Homework
• Write a program to add two numbers and display the sum.

• Write a program for calculating the simple interest using the formula SI=

(PTR)/100, where, P denotes the principal, T time and R rate of interest.

• Write a program to decide whether a number is positive or negative.

• Write a program to test a number for even or odd.

• Write a program to calculate area (=PI*r*r) and circumference (2*PI*r) of a

circle having radius r. The radius r should be taken from user.

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 Contd…,
• Ram’s basic salary is input through the keyboard. His dearness allowance is
40% of basic salary, and house rent allowance is 20% of basic salary. Write
a program to calculate his gross salary.

• The distance between two cities (in km.) is input through the keyboard.
Write a program to convert and print this distance in meters, feet, inches
and centimeters. [Note: 1km=1000 meter, 1km= 3280.84 feet, 1 km=
39370.08 inches, and 1 km= 100000 centimeter].

• Write a program which reads radius of sphere from keyboard and calculates
its volume and area [ hint: volume=4PIr3/3 and Area= 4PIr2].

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 Contd…,
• Write a program to read three sides of a triangle and calculate the area (
Note: area= sqrt(s*(s-a)*(s-b)*(s-c)) where, s=(a+b+c)/2).

• If the marks obtained by a student in five different subjects are input

through the keyboard, find out the aggregate marks and percentage marks
obtained by the student. Assume that the maximum marks that can be
obtained by a student in each subject is 100.

• A cloth shop during festival seasons offers a discount of 10% on all

purchases made in that shop. The total amount after discount for a
customer is given as Rs.1000.5. Write a program to calculate and display
the discount, and amount before discount.
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 Contd…,
• Write a program to find the size of each primitive data types in your
system.

• Write a program that requests two float type numbers from the user and
then divides the first number by the second and display the result along
with the numbers.

• Write a program to read the price of an item in decimal form (like 15.95
Rs) and print the output in Paisa (like 1595 Paisa).

• If the total selling price of 15 items and the total profit earned on them is
input through the keyboard, write a program to find the cost price of one
item.

• Write a program to decide whether a input number is less than 100 or not.

• Write a program that prints the even numbers from 1 to 100.

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 Contd…,
• Write a program to read number of days from the user and convert them
into months and days.
• Write a program to read two integer number ( number of male and female )
and finds the ratio between them to express as floating point value.
• Write a program to read two integer value m and n and decide and print
whether m is a multiple of n.
• Write a program to find the sum of the series following series and display
the result. 1+1/2+1/3 + …….1/n. Take the value of n from the user.
• Write a program that evaluate the expression: a=5<=8&&6!=5 and display
the result on the screen.
• Write a program that evaluate the expression: x=a-b/3+c*2-1 and display
the result on the screen. Note take the value of variables from the user.

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 Contd…,
• Write a program to determine whether a given number is ‘odd’ or ‘even’ and print
the message number is even or number is odd.

• Write a program that reads four values a, b, c and d from the terminal and evaluates
the ratio of (a+b) and (c-d) and prints the result, if (c-d) is not equal to zero,
otherwise print the appropriate message on the screen.

• If the ages of Ram, Shyam and Ajay are input through the keyboard, write a
program to determine the youngest of the three.

• While purchasing certain items, a discount of 10% is offered if the quantity

purchased is more than 1000. If quantity and price per item are input through the
keyboard, write a program to calculate the total expenses.

• Write a Program to read two numbers and an arithmetic operator from the user,
program performs the operation on input data based on input arithmetic operator
and display the result (note: use else..if ladder).
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 Contd…,
• If cost price and selling price of an item is input through the keyboard, write a
program to determine whether the seller has made profit or incurred loss. Also
determine how much profit he made or loss he incurred.

• The current year and the year in which the employee joined the organization are
entered through the keyboard. If the number of years for which the employee has
served the organization is greater than 3 then a bonus of Rs. 2500/- is given to the
employee. If the years of service are not greater than 3, then the program should do
nothing.

• Write a program to finding the grading of students based on the marks entered by
the user. ( Note: use switch statement).

• Write a Program to read two numbers and an arithmetic operator which performs
the specified operation and display the result (note: use Switch statement).

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 Contd…,
• Write a c program that reads a value in the range 1 to 12 and print the name of that
month. Print error for any other input value.
• Write a program to checks whether an year (integer) entered by the user is a leap
year or not (Note: A leap year is exactly divisible by 4 except for century years
(years ending with 00). The century year is a leap year only if it is perfectly
divisible by 400.).
• The marks obtained by a student in 5 different subjects are input through the
keyboard. The student gets a division as per the following rules:
– percentage above or equal to 80 – Distinction division
– Percentage between 60 and 79 - First division
– Percentage between 50 and 59 - Second division
– Percentage between 40 and 49 - Third division
– Percentage less than 40 - Fail
Write a program to calculate the division obtained by the student.
• Write a program to find the sum of first n natural numbers.

• Write a program to find the sum and average of first n natural numbers.

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 Contd…,
• Write a program to find the sum of square of first n natural numbers.
• Write a program to display the Fibonacci sequence of first n numbers
(entered by the user) using loop.
• Write a program to generate a multiplication table of a number entered by
the user.
• Write a program that reads weight and height of boys in a class and then
count the number of boys whose weight is less than 50 kg and height is
greater than 170 cm.
• Write a program to find the number of and sum of all integers greater than
100 and less than 200 that are divisible by 7.
• Write a program that read the code 1 for a boy and 2 for a girl and then
count the number of boys and girls in a class based on the entered code.

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 Contd…,
• Write a program to take a number from the user and then count the number
of digits in that number.

• Write a program to find the sum of digits of a number entered by the user.

• Write a program to reverse the number entered by the user.

• Write a program to Check Whether a Number entered by the user is

Palindrome or Not

• Write a program to check whether a number entered by the user is prime or

not.

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 Thank You !

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