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Matthayom 3 Computer Science Supplementary Class on Programming with C#, Lesson 3
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VARIABLES & EXPRESSIONSM3 COMPUTER SCIENCE CLASS – TERM 2
THE PRINCE ROYAL'S COLLEGE
WHAT IS THE BASIC C# SYNTAX?
BASIC C# SYNTAX:
•C# code is made of a series of statements where
each statement ends with a semicolon “;”
•C# code is organized in “blocks”, which may
contain any number of statements, and are
bounded by braces “{” and “}”
{
<code line 1, statement 1>;
<code line 2, statement 2>
<code line 3, statement
2>;
}
LAYOUT OF A BLOCK OF CODE IN C#
WHAT IS A COMMENT?
•A comment is a descriptive text added to a
code. It is not executed/run because it is not
really part of the program code.
•Examples:
/* This is a comment */
// This is a different sort of comment.
/// A special comment
WHAT ARE VARIABLES?
•Variables store data which can be used and
changed within a program; in C# they have to
be assigned a name and a type first before they
can be used in C#
•C# syntax for declaring variables merely
specifies the type and variable name:
<type> <name>;
EXAMPLES OF VARIABLES:
• Integer TypesType Alias For Allowed Values
sbyte System.SByte Integer between −128 and 127
byte System.Byte Integer between 0 and 255
int System.Int32 Integer between −2147483648 and 2147483647
uint System.UInt32 Integer between 0 and 4294967295
long System.Int64 Integer between −9223372036854775808 and 9223372036854775807
ulong System.UInt64 Integer between 0 and 18446744073709551615
EXAMPLES OF VARIABLES:• Floating Types
• Text and Boolean Types
Type Alias For MIN/MAX Values
float System.Single 1.5 × 10−45 / 3.4 × 1038
double System.Double 5.0 × 10−324 / 1.7 × 10308
decimal System.Decimal 1.0 × 10−28 / 7.9 × 1028
Type Alias For Allowed Values
char System.Char One Unicode character, stored as an integer between 0 and 65535
bool System.Boolean Boolean value, true or false
string System.String A sequence of characters
HOW DO YOU NAME VARIABLES?
• The first character of a variable name must be either a
letter, an underscore character(_), or the at symbol
(@).
•Next characters may be letters, underscore characters,
or numbers.
•C# is case sensitive, so be careful and remember the
exact case used when you declare your variables.
WHAT ARE EXPRESSIONS?
•Basic building blocks of computation made by
combining variables and operators.
WHAT ARE OPERATORS?•Symbols that tells the compiler to perform
specific mathematical or logical manipulations.
• TYPES OF OPERATORS:
• Arithmetic Operators
• Relational Operators
• Logical Operators
• Bitwise Operators
• Assignment Operators
• Miscellaneous Operators
WHAT ARE OPERATORS?•Symbols that tells the compiler to perform
specific mathematical or logical manipulations.
• TYPES OF OPERATORS:
• Arithmetic Operators
• Relational Operators
• Logical Operators
• Bitwise Operators
• Assignment Operators
• Miscellaneous Operators
MATH OPERATORS:Operator
Sample Result
+ var1 = var2 + var3;
var1 is assigned the value that is the sum of var2 and var3
- var1 = var2 -var3;
var1 is assigned the value that is the value of var3 subtracted from the value of var2
* var1 = var2 * var3;
var1 is assigned the value that is the product of var2 and var3.
/ var1 = var2 / var3;
var1 is assigned the value that is the result of dividing var2 by var3
% var1 = var2 % var3;
var1 is assigned the value that is the remainder when var2 is divided by var3
STRING CONCATENATION OPERATOR:Operator
Sample Result
+ var1 = var2 + var3;
var1 is assigned the value that is the concatenationof the two strings stored in var2 and var3
INCREMENT AND DECREMENT OPERATORS:Operator
Sample Result
++ var1 = ++var2; var1 is assigned the value of var2 + 1. var2 is increased by 1var1 = var2++;
-- var1 = --var2; var1 is assigned the value of var2 - 1. var2 is decreased by 1var1 = var2--;
ASSIGNMENT OPERATORS:Operator
Sample Result
= var1 = var2; var1 is assigned the value of var2
+= var1 += var2; var1 is assigned the value that is the sum ofvar1 and var2
-= var1 -= var2; var1 is assigned the value that is the value of var2 subtracted from the value of var1.
*= var1 *= var2; var1 is assigned the value that is the product of var1 and var2.
/= var1 /= var2; var1 is assigned the value that is the concatenationof the two strings stored in var2 and var3.
%= var1 %= var2; var1 is assigned the value that is the remainder when var1 is divided by var2
Priority Operators
Highest ++, -- (used as prefixes); +, - (unary)
*, /, %
+, -
=, *=, /=, %=, +=, -=
Lowest ++, -- (used as suffixes)
ORDER OF OPERATORS:
SOURCES
• "Tutorials Point." C# Tutorial. N.p., n.d. Web. 20 Nov. 2014.
• "Variables." The Complete C# Tutorial. N.p., n.d. Web. 20 Nov.
2014.
• "C# Programming." Wikibooks. N.p., n.d. Web. 20 Nov. 2014.
• Watson, Karli, Jacob Vibe Hammer, John D. Reid, Morgan
Skinner, Daniel Kemper, and Christian Nagel. Beginning Visual
C#® 2012 Programming. Indianapolis: John Wiley and Sons,
2013. Print.
THE END