The document outlines basic programming constructs including variables, constants, and data types in C#. It explains how to declare variables and constants, along with the characteristics of various data types, such as value types and reference types, and their usage. Additionally, it discusses console input/output operations and string concatenation in the context of C# programming.

1. Basic Programming Constructs

2. Variable
Programmer-defined word that holds the value of the
user.
Portion of the memory to store a determined value.

3. Rules in Declaring variables
 It must begin with a letter or underscore (_), then followed by a letter, digit, or underscore.
 It must not include blanks.
 It must not be the keywords, which are reserved words by the language.
 It must not be given a name with the same name as other functions.

4. Constant
 Expression with a fixed value that cannot be changed at runtime.
 To declare a constant in C#, the const keyword is used.
 To define a constant, this syntax should be followed:
 Const <data_type> <constant_name> = value;

5. Literals
 Values within the source code of a program.
 Examples a= 5; 5 in this piece of code is a literal constant.
 Literal Constant can be integer numerals, floating-pointing numerals, characters, strings , or
Boolean values.

6. Integer literals
 Constant and are also called decimal numerals.
 For example
235
612
18
29

7. Floating-point literal
 Numbers with decimals, fractions, and /or exponents.
 For Example:
3.14159 // 3.14159
6.02e23 // 6.02 x 10

8. Character and String
 Non-numeric constant like
‘z’ – character
‘j’ – character
‘a’ – character
“jasmin” – string
“Hello World” - string

9. Data type
 Variable allocated in the computer’s memory.
 Variable should be identified based on the type of data it can hold.
 Data types categorized as value types and reference type.

10. Value type
 Holds data within its own memory location

11. Reference type
 Contains a pointer to another memory location that holds the data.
int a = 42;
char ch = ‘A’;
bool result = true; Value types
object obj = 42;
string str = “Hello”;
byte[] bytes = {1,2,3}; - Reference type

12. Characteristics of a Data type
 Name – value type
 Size – how much memory they use
 Default value – the initial value

13. Type Description Range Represent
bool Represent True or false True or False Boolean Value
sbyte Signed byte -128 to 127 8-bit signed integer type
byte Unsigned byte 0 to 255 8-bit unsigned integer
short Short integer -32,768 to 32,767 16-bit signed integer type
ushort Unsigned short integer 0 to 65,535
16-bit unsigned integer
type
int Integer
-2,147,483,648 to
2,147,483,647
32-bit signed integer type
uint Unsigned integer 0 to 4,294,967,295
32-bit unsigned integer
type
long 64-bit signed integer type
-
9,223,372,036,854,775,808
to
9,223,372,036,854,775,808
64-bit signed integer type
ulong Unsigned long integer
0 to
18,446,744,073,709,551,61
5
64-bit unsigned integer
type
decimal
Use this data type for
currency value
(-7.9 x 1028to 7.9 x 1028
) /10 0 to 28
128-bit precise decimal
values with 28-29
significant digits

14. Type Description Range Represent
float Floating point number
-3.4 x 1038 to +3.4 x 1038 32-bit single-precision
floating point type
Double Double floating point
(+/-) 5.0 x 10-324 to (+/-
)1.7 x 10308 64-bit double-precision
floating point type
Char Unicode character Any valid character
16-bit Unicode
character

15.  C# supports unsigned data types for short, long and int which uses letter ‘u’ + data type for
identification
 Unsigned used to exclude the negative sign while signed data types are value can have a negative
number
 Example int -247 and Uint 247

16. Reference types
Reference type Description Size
Object Base type of all other types 8+ bytes
String Character array 20+bytes

17. Reference types
 A variable is declared like this:
<data type><variable>;
 Example:
string name;
int a,b,c;
 Variable can have an initial value by adding a value to it during its declaration. It is declared as:
 <Data type > <variable name> = value;
 Example
int a=5;
double B= 2.9;
double pi= 3.1416

18. ushort years= 2000;
decimal decimalPI= 3.141592653589793238m;
bool isEmpty= true;
char ch= ‘a’;
string firstName =“John”;
ch = (char)5;
char secondChar;
// Here we use an already initialized variable and reassign
it
secondchar = ch;

19. What is a Console

20. Console
A window, which users can interact with in a system program.
Interaction can be by text input from standard input (keyboard),
text display standard output (monitor), or simply input-output
operations.
System.Console class has different properties and methods
which are used to read and display text on the console as well
as its formatting.

21. What are C# Input/Output
Statement

22. I/O statement
Used for user and computer interaction.
It uses the standard input stream Console.
Print information on the standard output stream Console.Out,
and can signal for problem situations in the standard error
stream Console.Error.
Example: Console.Out.WriteLine(“Hello World”);
Output: Hello World

23. Console.Write/WriteLine
Method that can print all basic types (string, numeric, and
primitive type).
Console.Write writes the text and places the cursor after the last
character while the Console.
WriteLine writes the text and places the cursor to the next line.

24. Example
// Print String
Console.WriteLine(“Hello World);
//Print int
Console.WriteLine(5);
// Print Double
Console.WriteLine (3.141512412412)

25. Output
Hello World
5
3.141512412412

26. String Concatenation
 Combining two strings and returns as a result of a new string.
 C# uses ‘+’ operator to concatenate two strings.
 For example:
string age = “twenty-six”;
String text = “ He is” + age + “years old”;
Console.WriteLine(text);
Output: He is twenty-six years old.

27. Mixed String Concatenation
 Concatenation can be done alternately with a variable.
 Composed of an output text followed by a variable then another output
text.
 Example
int age = 26;
String text = “He is “ + age + “years old. “ ;
Console.WriteLine(text);

28. Console.Read/ReadLine()

29. More Example