1. CSCI 3328 Object Oriented Programming in C# Chapter 4: C# Control Statement – Part I
UTPA – Fall 2012
This set of slides is revised from lecture slides of Prof. John Abraham. -- Xiang Lian

2. Objectives In this chapter, you will:
Learn the primitive data types in Visual C#
Become familiar with arithmetic operators
Explore how to design algorithms to solve problems
Learn the components of basic control structures
Study the syntax of basic sequence, selection, and repetition structures in Visual C#

3. Introduction Computer program Programming
Sequence of statements whose objective is to accomplish a task
Programming
Process of planning and creating a program

4. Introduction (cont'd) Function Syntax Programming language
Collection of statements; when executed, accomplishes something
Syntax
Rules that specify which statements (instructions) are legal
Programming language
A set of rules, symbols, and special words
Visual C#

5. Introduction (cont'd) Reserved words, keywords, or word symbols
Words that are reserved by Visual C#
Usually in blue color in the IDE (Visual Studio)

6. About Some Data Types in C#
Value Types Size (in bits) Range sbyte to 127 byte to 255 short to ushort to int to uint to long to ulong to char to 65535
bool true, false
enum types and struct types
Reference types include class types, interface types, delegate types, and array types
Pointer types

7. Declaration of Variables
All variables must be declared before they are used in a program
Declaring a variable
int product = 3;
Declaring multiple variables of the same type
int number1, number2;

8. Naming Convention
Consist of letters, digits, and the underscore character (_)
Must begin with a letter or underscore
C# is case sensitive
NUMBER is not the same as number

9. Arithmetic Operators in Visual C#
Addition: +
Subtraction: -
Multiplication: *
Division: /
Modulus: %
Increment: ++
Decrement: --

10. Explicitly and Implicitly Converting Between Simple Types
Integer and integer division yields integer result
Suppose average is a floating point number:
Average = total/num; Average will only get an integer if total and num are integers.
int sum = 200, num = 3;
float av;
av = sum / num;
Console.WriteLine(av);
// Output: 66

11. Unary Cast Operator int sum = 200, num = 3; float av;
av = (float) sum / num;
Console.WriteLine(av);
// Output:
float/float or float/int or int/float will yield a float.
C# implicitly promotes the one int to float

12. Division and Modulus x / y and x%y E.g., 7.0 / 2 evaluates to 3.5
int x=7, y = 2;
Console.WriteLine(x / y);
Console.WriteLine(x % y);
E.g., 7.0 / 2 evaluates to 3.5

13. Last Chapter: Arithmetic Operators
Unary: +, -
Multiplicative: *, /, %
Additive: +, -
Relational operators
> < >= <=
Equality operators
==, !=
Precedence of operators
high
low

14. Exercises What are the values of the following expressions?
10/3
5.2/2.0
9 % 3
What is the order of the following expression?
X = 2 * 5 / 3+ 3 * 5 + 7

15. Control Statements Linear (sequential) program execution
Selection structure
repetition structure
Structured programming
Controlled entry and exit out of a module
Avoid goto statements

16. Selection Structures in C#
if – single selection statement
if … else – double selection statement
switch – multiple selection statement
[grade>=60]
display "passed"
[grade<60]

17. Examples if (grade >= 60) else Conditional Operator
Console.WriteLine("Passed!");
else
Console.WriteLine("Failed!");
Conditional Operator
Console.WriteLine(grade >= 60 ? "Passed!": “Failed!”);

18. Nested If Statement
if (grade >=90) Console.WriteLine(“A”); else if (grade >=80) Console.WriteLine(“B!”); … else Console.WriteLine(“F!”);

19. Repetition Structure - while
Read LCV (initialize)
while (condition) {
Block
Read LCV again (change value) }

20. Example length = Convert.ToInt16(Console.ReadLine());
while (length > 0) {
Console.Write("Enter Height of the Wall: ");
height = Convert.ToInt16(Console.ReadLine());
PaintAWall thisWall = new PaintAWall(length, height, pricePerGal);
thisWall.CalculateCost(ref paintCost, ref laborCost, ref galPaint, ref sqFt);
Console.Write("Enter Length and Height for Wall #: " + Convert.ToString(numWalls+1));
Console.Write("\nEnter Length of the Wall (0 to quit): "); }

21. Counter Controlled vs Sentinel Controlled
Counter controlled while loop (use LCV as a counter)
int Counter =1;
while (Counter <=10) { …
Counter ++;
}//does it 10 times
increment operator

22. Counter Controlled vs Sentinel Controlled (cont'd)
Sentinel controlled while loop
string str;
while (str != "0") { …
str = Console.ReadLine();
}//does it until str is "0"
Sentinel controlled is good when one does not know exact number of times to execute a loop

23. Example of while Loop int product = 3; while (product <= 100)
product = 3*product;

24. Nested Control Statements
class MultiplicationTable { static void Main(string[] args) int i=2, j; while (i <= 12) j = 1; while (j <= 10) Console.WriteLine(i + " x " + j + " = " + i * j ); j++; } Console.WriteLine("\n"); i++;

25. Exercises
Write a console program using nested while loop to output the following pattern to screen: * **
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