CSCI 3328 Object Oriented Programming in C# Chapter 4: C# Control Statement – Part I 1 Xiang Lian The University of Texas Rio Grande Valley Edinburg, TX

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# 2

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

Introduction (cont'd) Function – 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# 4

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) 5

About Some Data Types in C# Value Types Size (in bits) Range sbyte to 127 byte 8 0 to 255 short to ushort 16 0 to int to uint 32 0 to long to ulong 64 0 to char 16 0 to bool 8 true, false enum types and struct types Reference types include class types, interface types, delegate types, and array types Pointer types 6

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; 7

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 8

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

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 avg; avg = sum / num; Console.WriteLine(avg); // Output: 66 10

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 11

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

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

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 *

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

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

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

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

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

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): "); length = Convert.ToInt16(Console.ReadLine()); } 20

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 21 increment operator

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 22

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

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++; } 24

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