Chapter 12 Enumerated, Structure, Objectives and Union Types · To use enumerated types, ... data...

Computer Science: A Structured Programming Approach Using C 1

Objectives

❏ To introduce the structure, union, and enumerated types

❏ To use the type definition statement in programs

❏ To use enumerated types, including anonymous types.

❏ To create and use structures in programs

❏ To be able to use unions in programs

❏ To understand the software engineering concept of coupling and

to be able to evaluate coupling between functions.

Chapter 12

Enumerated, Structure,

and Union Types


FIGURE 12-1 Derived Types


12-1 The Type Definition (typedef)

Before discussing the derived types, let’s discuss a C

declaration that applies to all of them—the type

definition. A type definition, typedef, gives a name to a

data type by creating a new type that can then be used

anywhere a type is permitted.


FIGURE 12-2 Type-definition Format

typedef int INGETER;


12-2 Enumerated Types

The enumerated type is a user-defined type based on the

standard integer type. In an enumerated type, each

integer value is given an identifier called an enumeration

constant.

Declaring an Enumerated Type

Operations on Enumerated Types

Enumeration Type Conversion

Initializing Enumerated Constants

Anonymous Enumeration: Constants

Input/Output Operations

Topics discussed in this section:

Declaring an Enumerated Type

enum typeName {identifier list};

enum color {RED, BLUE, GREEN, WHITE};

enum color skyColor;


Operations on Enumerated Types enum color x, y;

x = BLUE; x = y;

if (color1 == color2)if (color1 == BLUE)

Switch (color1){case BLUE: …


Enumeration Type Conversion

int x; enum color y;x = BLUE; y = 2;

enum color y;y = (enum color) 2;


Initializing Enumerated Constants enum months {JAN, FEB, MAR, APR};

enum months {JAN = 1, FEB, MAR, APR};

enum color {RED, ROSE = 0, CRIMSON = 0, BLUE, AQUA = 1};


Anonymous Enumeration: Constants enum {space = ‘ ‘, comma = ‘,’,

color = ‘:’};

enum {OFF, ON};



PROGRAM 12-1 Print Cable TV Stations


Don’t be confused about strings and enumerated types.

“Jan” is a string made of three characters; JAN

as defined in the previous code example, is an

enumerated type (identifier) which

has the integer value 1.

Note


12-3 Structure

A structure is a collection of related elements, possibly

of different types, having a single name.

Structure Type Declaration

Initialization

Accessing Structures

Operations on Structures

Complex Structures

Structures and Functions



FIGURE 12-3 Structure Examples


Elements in a structure can be of the same or different types.

However, all elements in the structure

should be logically related.

Note


FIGURE 12-4 Tagged Structure Format


FIGURE 12-5 Structure Declaration with typedef


FIGURE 12-6 Structure Declaration Format and Example


FIGURE 12-7 Initializing Structures


FIGURE 12-8 Structure Direct Selection Operator


PROGRAM 12-2 Multiply Fractions


FIGURE 12-9 Copying a Structure


FIGURE 12-10 Pointers to Structures


(*pointerName).fieldName pointerName->fieldName.

Note


FIGURE 12-11 Interpretation of Invalid Pointer Use


FIGURE 12-12 Indirect Selection Operator


PROGRAM 12-3 Clock Simulation with Pointers


FIGURE 12-13 Nested Structure


FIGURE 12-14 Arrays in Structures


FIGURE 12-15 Pointers in Structures


FIGURE 12-16 Array of Structures


PROGRAM 12-4 Sort Array of Student Structures


FIGURE 12-17 Passing Structure Members to Functions


FIGURE 12-18 Passing and returning structures


PROGRAM 12-5 Passing and Returning Structures


FIGURE 12-19 Passing Structures Through Pointers


PROGRAM 12-6 Passing Structures through Pointers


12-4 Unions

The union is a construct that allows memory to be

shared by different types of data. This redefinition can

be as simple as redeclaring an integer as four

characters or as complex as redeclaring an entire

structure.

Referencing Unions

Initializers

Unions and Structures

Internet Addresses



FIGURE 12-20 Unions


PROGRAM 12-7 Demonstrate Effect of Union


FIGURE 12-21 A Name Union


PROGRAM 12-8 Demonstrate Unions in Structures


PROGRAM 12-9 Convert IP Address to long


12-5 Programming Application

In this section, we develop a program that simulates

the operation of an elevator. The elevator serves floors

from zero (the basement) to the top floor. The elevator

is very old and is not fully automatic. When people

enter the elevator, they enter their desired floor

number.


FIGURE 12-22 Elevator Structure


FIGURE 12-23 Elevator Structure Chart


FIGURE 12-24 Elevator State Diagram


PROGRAM 12-10 Elevator: main


PROGRAM 12-11 Elevator: Initialize


PROGRAM 12-12 Elevator: Run Elevator


PROGRAM 12-13 Elevator: Move


PROGRAM 12-14 Elevator: Move Up and Move Down


PROGRAM 12-15 Elevator: Any Up and Any Down Request


PROGRAM 12-16 Elevator: Time Pass


PROGRAM 12-17 Elevator: Terminate


12-6 Software Engineering

In this section we discuss two important aspects of

program design: function coupling and data hiding.

Coupling

Data Hiding



Well-structured functions are highly cohesive

and loosely coupled.

Note


Stamp coupling should pass only the data needed.

Note


Don’t bundle unrelated data to reduce the

number of parameters.

Note


Control coupling should be used only to pass status.

Note


Avoid global coupling within a program.

Note


Never use content coupling.

Note


Programming Standard:

Do not place any variables in the global area of a program.

Note

Chapter 12 Enumerated, Structure, Objectives and Union Types · To use enumerated types, ... data...

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