1. CS148 Introduction to Programming II
Ayman Abdel-Hamid
Department of Computer Science
Old Dominion University
Lecture 4: 1/27/2003
Lecture 4: 1/27/2003
CS148 Spring 2003

2. Outline Simple versus Structured data types C++ Structs
Lecture 4: 1/27/2003
CS148 Spring 2003

3. Simple vs. Structured Data Types
Simple Data types (int, float, double, char, ..)
A value is a single data item (can not be further broken into components)
Structured Data types
A value is a collection of components items
Entire collection given a single name
Each component can be accessed individually
string name = “Ayman”;
cout << name[3];
Lecture 4: 1/27/2003
CS148 Spring 2003

4. C++ Structs (Records)
Record is heterogeneous structured data type (components can be of different data types, each component called a field)
In C++, a record is called a structure, fields called members, each member has a member name
Why do we need a struct?
Student information (int Sid; string name; float GPA)
How about if we have 100 students, we need to declare 3 arrays, one for Student ID, name, and GPA
Alternative: Declare a student record having as members (Sid, name and GPA), and declare one array of student records
Lecture 4: 1/27/2003
CS148 Spring 2003

5. Example struct StudentRec { int Sid; string name; float GPA;
}; //struct declaration
//declare a variable of type StudentRec
//struct members associated with actual memory locations
StudentRec aStudent;
cin >> aStudent.Sid >> aStudent.name;
aStudent.GPA = 3.5f;
cout << aStudent.Sid << aStudent.name; //member selector (dot notation)
Lecture 4: 1/27/2003
CS148 Spring 2003

6. Aggregate Operations on Structs
An aggregate operation is an operation on a data structure as a whole, as opposed to an operation on an individual component of the data structure
Operation Allowed
I/O No
Assignment Yes
Arithmetic No
Comparison No
Argument Passage Yes (by value or by reference)
Return as function’s return value Yes
Lecture 4: 1/27/2003
CS148 Spring 2003

7. Examples on aggregate operations
StudentRec st1, st2;
st1 = st2; //allowed since both are of type StudentRec
st1 = st2 + 10; //Not allowed
if (st1 < st2) //Not allowed
cin >> st1; //Not allowed
cout << st1; //Not allowed
cin >> st1.Sid; //Allowed
Lecture 4: 1/27/2003
CS148 Spring 2003

8. Alternative Forms of struct declarations
//mix struct declaration with variable declaration
//Better to keep them separate for clarity and separation of notions
struct StudentRec {
int Sid;
string name;
float GPA;
} aStudent;
struct
int firstMember;
Float secondMember;
} someVar; //variable of anonymous data type
Lecture 4: 1/27/2003
CS148 Spring 2003

9. A struct member can be a function!
struct StudentRec {
int Sid;
string name;
float GPA;
string getName() { return name;};
float getGPA() { return GPA;};
}; //struct declaration
//declare a variable of type StudentRec
StudentRec aStudent;
cout << aStudent.Sid<< aStudent.getName() << aStudent.getGPA();
Lecture 4: 1/27/2003
CS148 Spring 2003

10. An array of structs struct StudentRec { int Sid; string name;
float GPA;
string getName() { return name;};
float getGPA() { return GPA;};
}; //struct declaration
//declare a variable of type StudentRec
StudentRec aStudent;
StudentRec Students[100];
cout << Students[10].Sid << Students[10].getName();
cout << Students[5].name[4];
Lecture 4: 1/27/2003
CS148 Spring 2003