Built- in Simple Types Enumerated Data Type Switch Statement

Sahar Mosleh California State University San Marcos Page 1

Built- in Simple Types

Enumerated Data Type

Switch Statement


Built- in Simple Types

- We have seen a number of simple built-in types- int, char, float, bool- by a simple type we mean not an array or …

- We have also seen (vaguely) how some of these types are represented

- An important attribute of a type is its size- how many bytes is required to store an “int”?- this is not an easy question to answer


Built- In Simple Types

- C++ provides the sizeof operator to find the size of a particular type

- For example:cout << sizeof(int) << “ ” << sizeof( char)

<< “ ” << sizeof( float) << endl;- This might print out

4 1 4- But then again, it might not…

- the sizes of the simple data types is compiler or architecture (machine-type) specific



- C++ does provide a number of different kinds of ints- short (or “short int”)- long ( or “long int”)

- C++ does guarantee that:

1 = sizeof(char) <= sizeof(short) <= sizeof(int) <= sizeof(long)

- In UNIX C++, sizeof(short)=2, sizeof(int)= 4, sizeof(long)=4

- For int types the maximum and the minimum size are - For Max = 2 (number of bits-1) -1 - For Min = 2 (number of bits-1)

< See Example 1 - part 1>



- Can also specify that an integer type is unsigned: represents a positive integer

unsigned int x;x = 0;x = -2; // This Does not give you the correct answer

- an unsigned int can hold values 0.. UINT_ MAX- an unsigned short can hold values 0.. USHRT_ MAX- an unsigned long can hold values 0.. ULONG_ MAX



Built-In Simple Types

- Why have unsigned numbers?

- tell the programmer and code-reader that a number is positive

- tells the compiler that a number is unsigned



- There are also different kinds of floating point numbers- float - standard floating point numbers- double - bigger floating point numbers- long double - bigger still floating point numbers

- As with int’s, the sizes of these types is not defined by the language but by the compiler/system

- Guaranteed:sizeof(float) <= sizeof(double) <= sizeof(long double)



- The standard head file float.h defines the limits on your system

#include <cfloat>

cout << FLT_ MIN << FLT_ MAX // smallest and largest float

cout << DBL_ MIN << DBL_ MAX // smallest and largest double

cout << LDBL_ MIN << LDBL_ MAX // smallest and largest // long double



Typedef

The typedef statement is the simplest way tocreate your own type

- essentially just gives a new name to an existing type- this will be more useful with more complex types in the future

- Syntax:

typedef ExistingTypeName NewTypeName;


Typedef

Example:typedef long double bigfloat;bigfloat x, y;

- define a new type bigfloat, which is the same as “long double”.

- can now declare variables/ parameters/ arrays, etc. of type bigfloat



Enumeration Types

- In C++, we can define a new type by listing the possible literal values that make up the possible values for the type

- called an Enumeration Type

- Example:enum Days {Sun, Mon, Tue, Wed, Thu, Fri, Sat};

defines a new type Days which has possible values Sun, Mon, Tue, Wed, Thu, Fri, Sat


Enumeration Types

For example:

enum Days {Sun, Mon, Tue, Wed, Thu, Fri, Sat};Days today;

today = Fri;

if (today == Sat) cout << “It’s saturday!!!\n”;

< See Example 1 - part 5&6>


Enumeration Types

- Rules and regulations for enumerated types

- the possible values for the type (Sun.. Sat in this case) are called enumerators


Enumeration Types

- Enumerations behave much as do ints

- In the Days example get equivalencies:

Sun Mon Tue Wed Thu Fri Sat0 1 2 3 4 5 6

- enumerators may be compared using all standard comparison operators

- the order of enumerators is the order of their corresponding int values- in this case Sun < Mon < Tue < ........


Enumeration Types

- Few functions are defined on enumerations- you can assign variables of enumerations- you can compare variables of enumerations- you cannot add, subtract, or increment (++) enumerations- you cannot read an enumeration directly- you can use an enumeration pretty much anywhere you use an int and it will use the corresponding int value- for example, if you print an enum type, it will print the corresponding int


Enumeration Types and Switch Statement

- Enumeration types can be used in a switch statement

Example of Switch statement:

Days today;…switch (today) {

case Sun: cout << “Sunday”; break;case Mon: cout << “Monday”; break;case Tue: cout << “Tuesday”; break;case Wed: cout << “Wednesday”; break;case Thu: cout << “Thursday”; break;case Fri: cout << “Friday”; break;case Sat: cout << “Saturday”; break;

}



Enumeration Types

- The iostream library does not support I/O of enumerated types

- To do output, typically do a switch statement much like the previous one

- Input is somewhat trickier- one possibility is to use integers to represent days


Enumeration Types

- Example: input of enumeration type using int to represent the enumerated type Days.

….int today_int;cout << "Enter today (0= Sun, 1= Mon, ..., 6= Sat): ";cin >> today_int;switch (today_int) {

case 0: today= Sun; break;case 1: today= Mon; break;case 2: today= Tue; break;case 3: today= Wed; break;case 4: today= Thu; break;case 5: today= Fri; break;case 6: today= Sat; break;default: cout << "Illegal day code " << endl; break;

};


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Built- in Simple Types Enumerated Data Type Switch Statement