1. Structures

2. Introduction
Structures are used to define related data in one construct.
An example of a structure:
typedef struct{
char name[20];
double avg;
int ID;
} student; …
student s;

3. Introduction (cont.) Another way to define a structure:
struct student{
char name[20];
double avg;
int ID; }; …
student s;

4. Structure I/O student s; cin>>s.name; cin>>s.avg;
cin>>s.ID; …
cout<<s.name;
cout<<s.avg;
cout<<s.ID;

5. Structure Assignment student s1={“ali“,70.5,2222}, s2;
s2.name=s1.name; //compiler error
strcpy(s2.name,s1.name);
s2.avg=s1.avg;
s2.ID=s1.ID;
//or
s2=s1; //ok
structures cannot be compared:
if (s1==s2) { //compiler error … }

6. Structure Comparison structures cannot be compared: student s={…},t;
if (s1==s2) { //compiler error … }
if (strcmp(s.name,t.name)==0 && s.avg==t.avg
&& s.ID==t.ID){ // ok

7. Arrays of structures struct student{char name[20]; int avg;};
student A[50];
//Read the data from the key board …
//Display the name of the student having maximum score
//Print names starting with ‘a’
//Sort the records in ascending order of the average
// Sort the records according to alphabetical order of names

8. Pointers to Structures
student s={“ali”,22222,90};
student * sptr;
sptr=&s;
cout<<(*sptr).name;
cout<<sptr->name;
sptr=new student;
cin>>sptr->name;
cin>>sptr->avg;
cin>>sptr->ID;

9. Arrays of Pointers to Structures
student * A[100];
for (int i=0; i<=99; i++){
A[i]=new student; }
//Read the data from the key board …
//Display the name of the student having maximum score
//Print names starting with ‘a’
//Sort the records in ascending order of the average and then according to
//alphabetical order of names. Exchange structures
//alphabetical order of names. Exchange pointers.

10. Nested Structures A structure can contain another structure: Example:
struct address{
char street[20];
char city[20];
char country[20] };
struct employee{
address a;
char name[20];
int ID;
float salary;
employee e; // nested structure
cin>>e.a.street;

11. Passing Structure by Value
struct point{double x; double y};
point midpoint(point p1, point p2){
point mid;
mid.x=(p1.x+p2.x)/2.0;
mid.y=(p1.y+p2.y)/2.0;
return mid; } …
point a={0.0,0.0}, b={5.0,10.0}, m;
m=midpoint(a,b);

12. Passing Structures by Address
void set_midpoint(point p1, point p2, point * mid){
mid->x=(p1.x+p2.x)/2.0;
mid->y=(p1.y+p2.y)/2.0; } …
point a={0.0,0.0}, b={5.0,10.0}, m;
set_midpoint(a,b,&m);

13. Passing Structures by Reference
void set_midpoint(point p1, point p2, point & mid){
mid.x=(p1.x+p2.x)/2.0;
mid.y=(p1.y+p2.y)/2.0; } …
point a={0.0,0.0}, b={5.0,10.0}, m;
set_midpoint(a,b,m);

14. Exercizes
Complete the following functions to find the student with the highest average and give an example on calling each of these.
student highest (student A[ ], int size){…}
student * highest(student A[ ], int size){…}
student highest(student *A[ ], int size){…}
void highest(student A[ ], int size, student& h){…}