Simple Data Types: Built-In
and User-Defined

	Additional C++ operators: +=, -=, *=, /=
	Statement Equivalent Statement
	i += 5; i = i + 5;
	pivotPoint *= n + 3; pivotPoint * (n + 3);
	The Cast Operation
		Two forms:
			intVar = (int) floatVar;
			intVar = int(floatVar); (only works if the data type name is a single identifier)
		myVar = (unsigned int) someFloat; (the only way for this one)

Working with Character Data

	Each computer uses a particular character set, two in substantial use today are ASCII and EBCDIC. The vast majority use ASCII.
	Character Issues:
		Comparing Characters: if (ch >= ‘a’ && ch <= ‘z’) – islower is preferred usage
		Converting Digit Characters to Integers: ‘9’ – ‘0’ = 9
		Converting to Lowercase and Uppercase: toupper and tolower can help (#include <cctype>)
		Accessing Characters Within a String: Use position number, e.g. ch = inputStr[2];

More on Floating-Point Numbers

	Comparing Floating-Point Numbers: check for an error within some range
	Underflow and Overflow: Numbers can be too large or too small to be represented.
	Cancellation Error: problems can occur when arithmetic operations occur on values of wildly different magnitudes: (1 + 0.00001234 – 1) = 0.00001234. For four digits of precision, this doesn’t work, why?

Practical Implications of
Limited Precision

	Limited precision has led to
		Mercury splashdown in unknown location, delaying the recovery of the spacecraft and the astronaut.
		Specialized high-tension cables linking a hydroelectric dam to the nearest power distribution point had to be redone due to precision problems.
		A bank employee stole infinitesimal amounts from a large number of accounts.

User-Defined Simple Types

	Enumeration Types – C++ allows the user to define a new simple type by listing (enumerating) the literal values that make up the domain of the type. These literal values are identifiers, not numbers, separated by commas.
	Example:
		enum Days (SUN, MON, TUE, WED, THU, FRI, SAT);

Enumeration Type Declaration

	EnumDeclaration
		enum Name {Enumerator, Enumerator, …};
	Enumerator
		Identifier = ConstIntExpression
	Legal or Illegal?
		enum Vowel {‘A’, ‘E’, ‘I’, ‘O’, ‘U’};
		enum Places {1st, 2nd, 3rd};
		enum Starch {CORN, RICE, POTATO, BEAN};
		enum Grain {WHEAT, CORN, RYE, BARLEY, SORGHUM};

More About Enumeration Types

	Consider the following declaration:
	enum Animals {RODENT, CAT, DOG, BIRD, REPTILE, HORSE, BOVINE, SHEEP};
	and the following variable declarations:
	Animals inPatient;
	Animals outPatient;
	Acceptable assignemnts are
	inPatient = DOG;
	outPatient = inPatient;
	someInt = DOG;
	inPatient = Animals(inPatient + 1);

Typical Usage of an
Enumeration Type

	switch (inPatient)
	{
	case RODENT   :
	case CAT      :
	case DOG      :
	case BIRD     : cout << “Cage ward”;
	break;
	case REPTILE  : cout << “Terrarium ward”;
	break;
	case HORSE    :
	case BOVINE   :
	case SHEEP    : cout “Barn”;
	break;
	}

Enumeration Type Input

	Enumeration types are known only internally to the program, they are input and output indirectly.
	string animalName;
	cin >> animalName;
	switch (toupper(animalName[0]))
	{
	case ‘R’ : if (toupper(animalName[1] == ‘O’)
	inPatient = RODENT;
	else
	inPatient = REPTILE;
	break;
	case ‘C’ : inpatient = CAT;
	break;
	.
	.
	.

Enumeration Type Output

	Enumeration types are known only internally to the program, they are input and output indirectly.
	switch (inPatient)
	{
	case RODENT :  cout << “Rodent”;
	break;
	case CAT    :  cout << “Cat”;
	break;
	case DOG    :  cout << “Dog”;
	break;
	case BIRD   :  cout << “Bird”;
	break;
	.
	.
	.
	}

Using a Value-Returning
Function for Input

	Animals StrToAnimal (/*in*/ string str)
	{
	Animals inPatient;
	switch (toupper(str[0]))
	{
	case ‘R’ : if (toupper(animalName[1] == ‘O’)
	inPatient = RODENT;
	else
	inPatient = REPTILE;
	break;
	case ‘C’ : inPatient = CAT;
	break;
	case ‘D’ : inPatient = DOG;
	break;
	.
	.
	.
	return inPatient;
	}
	}

User-Written Header Files

	User-defined data types can be useful in more than one program.
	Declarations can be placed in a header file and included using the #include directive.
	#include <iostream> looks in the standard include directory
	#include “months.h” looks in the current directory