The C# language fundamentals ( I ) P.F. Tsai

Hello World Project Please follow the instructions mentioned in the previous class to build a hello world project

Types C# is a strong typed language Weak Type: a value of one type is a bit-pattern which can be re- interpreted as a value of another type (C) Strong Type: a cast always involves a compile-time or run-time compatibility check, and a meaningful conversion. (JAVA & C#) Two sets of Types Intrinsic (built-in) types User-defined types Value types vs Reference types Stack vs Managed heap Declaration

Stack and Heap Stack The stack data structure First In Last Out Memory An area of memory supported by CPU and used to store local variables Pointed by the SP register Referred by the variable names Heap An area of memory managed by VM Garbage collector (GC)

Value types vs Reference types All intrinsic types are value types except for Object and String All user-defined types are reference types except for structs Examples: int myAge = 33; Variable contains the value string myName = “ Mandy ” ; Variable contains the address of the value

Intrinsic types (primitives)

Types frequently used bool True and false short, int & long Depends on your need Ram is CHEAP but time is EXPENSIVE Double, float(f) & decimal(m) Double is default float somefloat = 57f;

Types frequently used The char type represents a Unicode Unicode provides a unique number for every character no matter what the platform, program & language are chinese.html Example: char myChar = ‘ A ’ ; // ‘ \u0041 ’ use single quote  ‘ ‘ Escape characters For special purposes

Escape characters

Exercise 1 Please try to print the following message “ Hello World! ” (and BEEP!) trick: Console.Read();

Exercise 2 Please try to store your personal data into variables with corresponding types your name, age, gender, marriage, phone number, height, weight, birthday & your home address Ex: string name = “ Mandy Tsai ” ; // use double quote

Converting intrinsic types Objects of one type can possibly be converted into another type Implicit cast Explicit cast Example short x = 5; int y = x; //implicit int x = 5; short y = (short) x; // explicit

Exercise 3 Please try to figure out the value range of a short type variable and modify the above example (the explicit one) with assigning x a value outside the short- type range to see what happens then.

WriteLine() A formatted output Console.WriteLine( “ I am {0} years old and she is {1} years old “, myAge, herAge); An easier way Console.WriteLine( “ I am “ +myAge+ ” years old and she is “ +herAge+ ” years old ” );

More about WriteLine()

Exercise 4 Now you can modify your exercise 2 to show your personal information on the screen Example Name : Mandy Tsai Age : 33 Gender: Male …

Variables and Constants Initializing and assigning a value to a variable identifier case 1, 2 & 3

Identifer Names of your types, variables, methods, constants, objects and so forth Naming convection Camel notation for variables myVariable Pascal notation for methods and others MyFunctionName No clash with keywords

Case 1

Case 2

Case 3

Variables and Constants Constants A constant is a variable whose value can not be changed Memorizing names is much easier than numbers

Example

Exercise 5 Please try to implement the above example and modify the constant value to see what happens. FreezingPoint = FreezingPoint + 1; System.Console.WriteLine("Freezing point of water: {0}", FreezingPoint );

Enumerations An alternative to constants Value type A set of named constants (enumerator list) Restricted to integer types except for char

Examples Declare an enumeration define the type of constants

Example codes Access the constant by a dot operator Example 3-5 in the textbook (buggy) Declared outside Main() (int)

Special case

Conditional branching statements A conditional branch is created by a conditional statement, which is signaled by keywords such as if, else, or switch A conditional branch occurs only if the condition expression evaluates true Only boolean values are accepted here

If - else Unlike Matlab, it doesn ’ t need end Can be nested The code block use { } to mark the statement

Example codes

Operators will discussed later

Exercise 6 You need to write a program to evaluate the temperature of a batch tank, and specifically to return the following types of information: If the temperature is 50 degrees or lower, the program should warn you about temperature is way too low. If the temperature is between 50 to 70 degrees, the program should tell you that the process is under control. If the temperature is 70 degrees or higher, the program should warn you about temperature is way too high.

References C# programming 清華大學金仲達教授課程教材 嵌入式軟體聯盟 (Embedded Software Consortium)