Answers to Chapter 4 Review Questions

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Chapter 4

1:	What are namespaces used for in C# and .NET?
A:	Namespaces act as containers for classes. They help us organize the classes of our programs and to provide easy access to them (when reused) by outside parties.
2:	What is the advantage of including the keyword using followed by the name of a namespace in the beginning of a program?
A:	It allows us to write short names instead of long, fully-qualified names when we refer to classes in a namespace. This makes it easier to type the names and improves the readability of the source code.
3:	Which namespace contains classes related to mathematical calculations and console input/output.
A:	The System namespace.
4:	How should comments be applied in the source code?
A:	Like salt in your food, excessive amounts of comments are as damaging as too few comments.
5:	Describe a variable of type int.
A:	A variable of type int occupies 32 bits of memory and can represent whole numbers between 2147483648 and 2147483647.
6:	Why are x and y often regarded as unacceptable variable identifiers? Why are they acceptable in Listing 4.1?
A:	The identifiers x and y do not convey any information about what kind of value they represent, as opposed to names like accountBalance and height. However, x and y in Listing 4.1 represent a variety of values that cannot be pinpointed to a specific name, so the generic names x and y are acceptable.
7:	What are the fundamental parts of a method?
A:	A method header and its method body that is enclosed by curly braces.
8:	Why is MoveLeft a bad name for a class? For which C# construct would it be better suited?
A:	Classes generally represent items (tangible or conceptual) so nouns constitute better names for classes than verbs. Verbs, such as MoveLeft, are better suited to methods that take actions.
9:	How do you specify that a method does not return a value?
A:	By writing the keyword void in front of the method identifier in the method header.
10:	How do you specify that a method returns a value of type int?
A:	By writing the keyword int in front of the method identifier in the method header.
11:	What are arguments (in method calls)?
A:	The value of a method argument is passed along to the called method.
12:	What are formal parameters?
A:	A formal parameter is part of the method header and has a certain value as the execution of the method commences.
13:	How do arguments and formal parameters relate?
A:	Each argument of a method call is assigned to its corresponding formal parameter during a method call.
14:	Does the + operator only perform arithmetic additions?
A:	It has the potential (through operator overloading) to perform many different operations, depending on the types involved. We have seen examples of arithmetic addition and string concatenation.
15:	How can you break down the inner complexities of a class?
A:	By separating a few complex actions into several simpler actions (methods).
16:	What is a cohesive method?
A:	A method that accomplishes one clear task.

Answers to Chapter 4 Programming Exercises

1:	Change the multi-line comments in lines 3 6 to two single line comments.
2:	Apart from addition and multiplication, allow the user to perform a subtraction. Among other changes, you need to add a Subtract method. (The symbol is used to perform subtractions in C#).
A:	The following program contains answers to Exercise 1 and 2. The parts related to Exercise 1 and Exercise 2 are marked Ex.1 and Ex.2 respectively. using System; //Ex. 1 //This class finds the sum, product, difference, //min and max of two numbers public class SimpleCalculator { public static void Main() { int x; int y; Console.Write("Enter first number: "); x = Convert.ToInt32(Console.ReadLine()); Console.Write("Enter second number: "); y = Convert.ToInt32(Console.ReadLine()); Console.WriteLine("The sum is: " + Sum(x, y)); Console.WriteLine("The product is: " + Product(x, y)); Console.WriteLine("The maximum number is: " + Math.Max(x, y)); Console.WriteLine("The minimum number is: " + Math.Min(x, y)); Console.WriteLine("The difference is: " + Subtract(x, y)); //Ex. 2 } // Sum calculates the sum of two int's public static int Sum(int a, int b) { int sumTotal; sumTotal = a + b; return sumTotal; } // Product calculates the product of two int's public static int Product(int a, int b) { int productTotal; productTotal = a * b; return productTotal; } // Ex.2 // Subtract calculates the difference between two int's public static int Subtract(int a, int b) { int difference; difference = a - b; return difference; } }
3:	Instead of calculating the sum and the product of two numbers, make the program perform the calculations on three numbers. (You can ignore the Max and Min functions here.) Hint: You need to declare another int variable in Main. The Sum, Product, and Subtract methods must accept three arguments instead of two. You must allow the user to input a third number, and you must include the third argument when these methods are called.
4:	Create two methods called MyMax and MyMin that both take three arguments and find the maximum and minimum value of these arguments. Hint: Math.Max(Math.Max(a, b),c) returns the max of a, b and c.
A:	The following program constitutes answers to Exercises 3 and 4. It allows the calculations to be performed on three values and implements the MyMax and MyMin methods: using System; //This class finds the sum, product, difference, //min and max of three numbers public class SimpleCalculator { public static void Main() { int x; int y; int z; // Ex.3 Console.Write("Enter first number: "); x = Convert.ToInt32(Console.ReadLine()); Console.Write("Enter second number: "); y = Convert.ToInt32(Console.ReadLine()); // Ex. 3 Console.Write("Enter third number: "); z = Convert.ToInt32(Console.ReadLine()); Console.WriteLine("The sum is: " + Sum(x, y, z)); Console.WriteLine("The product is: " + Product(x, y, z)); // Ex. 4 Console.WriteLine("The maximum number is: " + MyMax(x, y, z)); Console.WriteLine("The minimum number is: " + MyMin(x, y, z)); // Ex.3 Console.WriteLine("The difference is: " + Subtract(x, y, z)); } // Ex. 3 // Sum calculates the sum of two int's public static int Sum(int a, int b, int c) { int sumTotal; sumTotal = a + b + c; return sumTotal; } // Ex. 3 // Product calculates the product of two int's public static int Product(int a, int b, int c) { int productTotal; productTotal = a * b * c; return productTotal; } // Ex. 3 // Subtract calculates the difference between two int's public static int Subtract(int a, int b, int c) { int difference; difference = a - b - c; return difference; } //Ex. 4 // Find max value of three parameters public static int MyMax(int a, int b, int c) { int max; max = Math.Max(a, Math.Max(b, c)); return max; } // Ex. 4 // Find min value of three parameters public static int MyMin(int a, int b, int c) { int min; min = Math.Min(a, Math.Min(b, c)); return min; } }

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