CS31-6 - CS 31 Introduction to Computer Science I Topic 6...

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.
Rohr All Rights
Reserved
JAR 6-1
CS 31 :
Introduction to
Computer Science I
Topic 6
Structs and Classes

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.
Rohr All Rights
Reserved
JAR 6-2
Structs
Vectors: One Data Type
•
A C++ vector is an aggregate data type
of multiple data items of the same type
•
Elements of a vector are accessed
by using an index

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.
Rohr All Rights
Reserved
JAR 6-3
Structs
Different Data Types
•
Some programs have multiple data items
of different types which can be grouped
together into a single data entity
•
A vector cannot be used because all the
elements of a vector must be the same
type of data (e.g. integer)

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.
Rohr All Rights
Reserved
JAR 6-4
Structs
Structs: Multiple Data Types
•
A C++ struct is an aggregate data type
of multiple data items which can hold
items of different types
•
Elements of a struct are accessed
by using a name

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.
Rohr All Rights
Reserved
JAR 6-5
Structs
Struct Definition
•
The definition of a struct specifies the
names and types of its member elements
•
Each member element has a unique
name and a type
•
Member elements can be any type of C+
+ data including simple variables,
vectors, and even other structs

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.
Rohr All Rights
Reserved
JAR 6-6
Structs
Struct Definition Example
struct TestData
{
int testNumber;
float voltage;
float current;
float power;
};

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.
Rohr All Rights
Reserved
JAR 6-7
Structs
Struct Definition Details
•
The definition of a struct begins with the
keyword struct followed by its name
•
An open brace precedes the declarations
of the member variables
•
Each member variable is declared in
order by type of data and member name

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.
Rohr All Rights
Reserved
JAR 6-8
Structs
Struct Definition Details
•
The end of the member variable
declarations is followed by a close brace
•
The definition must end with a semicolon
•
The definition is only a pattern
•
No actual data is created by the definition
Although technically allowed, variables are created in
declarations separate from the definition of the struct

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.
Rohr All Rights
Reserved
JAR 6-9
Structs
Struct Use
•
Once defined, an instance of a struct is
declared just like any other variable
•
The name of the struct is used like a type
•
Any number of instances of the struct
may be declared in a program
•
Each one must have a different name

CS 31: Introduction To CS
I
Topic 6: Structs and Classes
9/2009 John A.