1. Lecture 6: Structure and Class
solving quadric equations as an example
class
air-plane and bullets.
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

2. CS3369 Real Time Control Software/Wang Lusheng
Computing the roots of a quadric equation
The roots of a quadric equation ax2+bx+c=0 are
x1= (-b+( b2-4ac))/2ac
x2=x1= (-b- ( b2-4ac))/2ac
#include<iostream.h>
float x1, x2;
int flag=0;
void roots(float a, float b, float c)
void main(void) {
roots(1.0,2.0, 1.0);
if(flag == 0)
cout<<“The roots are”<<x1<<x2;
else
cout<<“No real root”; }
void roots(float a, float b, float c) {
if (b*b-4*a*c>=0)
x1=(-b+sqrt(b*b-4*a*c))/(2*a*c);
x2 =(-b-sqrt(b*b-4*a*c))/(2*a*c); }
else
flag=1;
x1, x2 and flag are used as global variables. Otherwise, function roots must return two values (we do not know how to do it.)
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

3. CS3369 Real Time Control Software/Wang Lusheng
Define structures
Structures are aggregate data types built using elements of other types.
We can use structure to group several variables together
struct two_roots {
float x1;
float x2;
} r;
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

4. Define a function of two_roots type
The function roots returns a value of type two_roots that contains two values of type float.
struct two_roots roots (float a, float b, float c)
{ two_roots r;
if (b*b-4*a*c>=0)
{ r.x1=(sqrt (b*b-4*a*c)-b)/(2*a*c);
r.x2=(-sqrt(b*b-4*a*c)-b)/(2*a*c);}
else
x3=100;
return r; }
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

5. Using structures in main()
In main function, we can print the two roots as follows;
#include <iostream.h>
int x3;
struct two_roots {
float x1;
float x2; };
struct two_roots roots (float a, float b, float c);
void main(void)
{ two_roots z;
z=roots(1.0, 2.0, 1.0);
if (x3==100)
cout<<“There is no real root”;
else
cout<<“The roots are”<< z.x1<<“ ”<<z. x2; }
struct two_roots roots (float a, float b, float c)
{ two_roots r;
if (b*b-4*a*c>=0)
{ r.x1=(sqrt (b*b-4*a*c)-b)/(2*a*c);
r.x2=(-sqrt(b*b-4*a*c)-b)/(2*a*c); }
else
x3=100;
return r;
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

6. CS3369 Real Time Control Software/Wang Lusheng
Time Services (Clock)
struct the_time {int hrs, int mins, int secs, int hundth;};
the_time get_time() {
the_time tmp;
int i,j,k,l;
_AH=0x2C; //service 0x2C for get time
interrupt(0x21); //interrupt 0x21
i=_CH; j=_CL; k=_DH; l=_DL;
tmp.hrs=i; tmp.mins=j; tmp.secs=k; tmp.hundth=l;
return tmp; }
void main()
{ the_time x;
x=get_time();
cout<<“The hour is ”<<x.hrs<<“The minute is ”<<x.mins;
cout<<“The second is ”<<x.sees;
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

7. Problem Solving: Student Records
We define a structure that can hold student records
structure student {
char name[20];
int student_id;
char grade; };
struct student x;
void main()
{int j;
cout<<“Please enter your name with <=20 characters\n”;
for(j=0; j<=19; j++)
cin>>x.name[j];
cout<<“Please enter your student number\n”;
cin>>x.student_id;
cout<<“Please enter the grade (A, B, C, D, F) \n”;
cin>>x.grade;
} Question: How to print out those input records?
The program asks
users to enter a
record of
students. Each
record contains
the name,
student_id and
grade.
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

8. Problem Solving: Student Records
We define a structure that can hold student records
structure student {
char name[20];
int student_id;
char grade; };
struct student x[56];
void main()
{int i,j;
for(i=0; i<=55; i++)
{ cout<<“Please enter your name with <=20 characters\n”;
for(j=0; j<=19; j++)
cin>>x[i].name[j];
cout<<“Please enter your student number\n”;
cin>>x[i].student_id;
cout<<“Please enter the grade (A, B, C, D, F) \n”;
cin>>x[i].grade;
} Question: How to print out those input records?
The program asks
users to enter 104
records of
students. Each
record contains
the nemae,
student_id and
grade.
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

9. CS3369 Real Time Control Software/Wang Lusheng
Classes
Classes enable the programmer to model objects that have attributes (represented as data members) and behaviors or operations (represented as member functions).
Object-oriented programming models real-world objects with software counterparts--classes
Objects of the same class have the same characteristics
e.g., cars, vehicles, air-planes, etc.
OOP encapsulates data (attribute) and functions (behavior) into packages called objects.
Objects have the property of information hiding.
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

10. CS3369 Real Time Control Software/Wang Lusheng
Classes (continued)
information hiding : objects may know how to communicate with each other, but do not know how other objects are implemented.
We can build software by combining “standardized, interchangeable parts” --classes.
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

11. Define air-plane as a class
void main(void) {
int driver = DETECT,mode;
int i,k,f=0,f3=0;
char x;
Air y1, y2, y3;
initgraph(&driver,&mode,"a:\\bgi");
setcolor(WHITE);
line(1,400,400,400);
for ( i = 0; i < 80; i++ )
setcolor(BLUE); y1.size=2; y1.planeshow(5*i, 5);
x=read_key();
if (x =='u') f=f-8;
if (x =='i') f=f+8;
if (x=='o') f3=f3-8;
if (x=='p') f3=f3+8;
setcolor(YELLOW); y2.size=4; y2.planeshow(5*(i-8), f);
setcolor(RED); y3.size=6;y3.planeshow(5*(i-16), f3);
delay (300);
y1.ereasep(5*i, 5); y2.ereasep(5*(i-8), f);
y3.ereasep(5*(i-16), f3); }
closegraph();
#include <graphics.h>
#include<dos.h>
#include<iostream.h>
#include<conio.h>
class Air{
public:
int size;
void planeshow(int i,int k);
void ereasep(int i, int k);
/*i decides the herizontal position */
/* k decides the vertical position */ };
void Air::planeshow(int i,int k) {
int j;
circle(i+5, 200+size+k, size);
circle(i+3, 200+2*size+k, size);
for (j=0; j<=4+3*size; j=j+size)
circle(i+j, 200+k, size);
circle(i+5, 200-size+k, size);
circle(i+3, 200-2*size+k, size); }
void Air::ereasep(int i, int k) {
int j;
setcolor(BLACK);
circle(i+5, 200+size+k, size);
circle(i+3, 200+2*size+k, size);
for (j=0; j<=4+3*size; j=j+1)
circle(i+j, 200+k, size);
circle(i+5, 200-size+k, size);
circle(i+3, 200-2*size+k, size); }
char read_key()
{ int y=1;
char x;
_AH=0x01;
geninterrupt(0x16);
y=_FLAGS&0x40;
if(y == 0)
_AH=0x00;
x=_AL;
return x; }
return '?';
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

12. Define air-plane as a class
void main(void) {
int driver = DETECT,mode;
int sf=0, i,k,f=0,f3=0;
char x;
Air y1, y2, y3;
initgraph(&driver,&mode,"a:\\bgi");
setcolor(WHITE);
line(1,400,400,400);
for ( i = 0; i < 120; i++ )
setcolor(BLUE); y1.size=2; y1.planeshow(5*i, 5);
x=read_key();
if (x =='u') f=f-8;
if (x =='i') f=f+8;
if (x=='o') f3=f3-8;
if (x=='p') f3=f3+8;
setcolor(YELLOW); y2.size=3; y2.planeshow(5*(i-8), f);
setcolor(RED); y3.size=3;
y3.planeshow(5*(i-16), f3);
if(x=='k'){sf=1; y2.shoot(5*(i-8), f);}
if (sf==0) delay (300);
else sf=0;
y1.ereasep(5*i, 5); y2.ereasep(5*(i-8), f);
y3.ereasep(5*(i-16), f3); }
closegraph();
#include<dos.h>
#include <graphics.h>
#include<iostream.h>
#include<conio.h>
class Air{
public:
int size;
void planeshow(int i,int k);
void ereasep(int i, int k);
void shoot(int i, int k); };
void Air::planeshow(int i,int k) {
int j;
circle(i+5, 200+size+k, size);
circle(i+3, 200+2*size+k, size);
for (j=0; j<=4+3*size; j=j+size)
circle(i+j, 200+k, size);
circle(i+5, 200-size+k, size);
circle(i+3, 200-2*size+k, size); }
void Air::ereasep(int i, int k)
setcolor(BLACK);
for (j=0; j<=4+3*size; j=j+1)
void Air::shoot(int i, int k)
{int j; sound(700);
for(j=0; j<=10; j++) {
setcolor(RED); line(i+j*30, 200+k,i+j*30+18, 200+k );
delay (30);
setcolor(BLACK); line(i+j*30, 200+k,i+j*30+18, 200+k); }
nosound();
char read_key()
{ int y=1;
char x;
_AH=0x01;
geninterrupt(0x16);
y=_FLAGS&0x40;
if(y == 0)
_AH=0x00;
x=_AL;
return x; }
return '?';
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

13. Define air-plane and Shoot classes
void Air::ereasep(int i, int k) {
int j;
setcolor(BLACK);
circle(i+5, 200+size+k, size);
circle(i+3, 200+2*size+k, size);
for (j=0; j<=4+3*size; j=j+1)
circle(i+j, 200+k, size);
circle(i+5, 200-size+k, size);
circle(i+3, 200-2*size+k, size); }
void Air::shoot(int i, int k)
{int j; sound(700);
for(j=0; j<=10; j++)
setcolor(RED); line(i+j*30, 200+k,i+j*30+18, 200+k ); delay (30);
setcolor(BLACK); line(i+j*30, 200+k,i+j*30+18, 200+k);
nosound();
#include<dos.h>
#include <graphics.h>
#include<iostream.h>
#include<conio.h>
class Air{
public:
int size;
void planeshow(int i,int k);
void ereasep(int i, int k);
void shoot(int i, int k);
/*i decides the herizontal position */
/* k decides the vertical position */ };
void Air::planeshow(int i,int k) {
int j;
circle(i+5, 200+size+k, size);
circle(i+3, 200+2*size+k, size);
for (j=0; j<=4+3*size; j=j+size)
circle(i+j, 200+k, size);
circle(i+5, 200-size+k, size);
circle(i+3, 200-2*size+k, size); }
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

14. Define air-plane and Shoot classes
void main(void) {
int driver = DETECT,mode;
int sf=0, i,k,f=0,f3=0, xi=0, yi=0;
char x;
Air y1, y2, y3;
Shoot bullet;
initgraph(&driver,&mode,"a:\\bgi");
setcolor(WHITE);
line(1,400,400,400);
for ( i = 0; i < 80; i++ )
setcolor(BLUE); y1.size=2; y1.planeshow(5*i, 5);
x=read_key();
if (x =='u') f=f-8;
if (x =='i') f=f+8;
if (x=='o') f3=f3-8;
if (x=='p') f3=f3+8;
setcolor(YELLOW); y2.size=3; y2.planeshow(5*(i-8), f);
if(x=='k'){sf=1; y2.shoot(5*(i-8), f);}
setcolor(RED); y3.size=3;y3.planeshow(5*(i-16), f3);
bullet.point(xi,yi);
if(x=='l') bullet.sh(xi,yi);
if (sf==0) delay (300);
else sf=0;
y1.ereasep(5*i, 5); y2.ereasep(5*(i-8), f);
y3.ereasep(5*(i-16), f3); }
closegraph();
class Shoot {
public:
void point(int i, int k);
void sh(int i, int k); };
void Shoot::point(int i, int k) {
setcolor(YELLOW); circle(400+i, 400+k, 1); }
void Shoot::sh(int i, int k)
{int j; sound(900);
for(j=0; j<=10; j++)
setcolor(RED);
line(400-j*30+i, 400+k-30*j,400-j*30+i-10, 400+k-30*j-10); delay (30);
setcolor(BLACK);
line(400-j*30+i, 400+k-30*j,400-j*30+i-10, 400+k-30*j-10);
nosound();
char read_key();
char read_key()
{ int y=1;
char x;
_AH=0x01;
geninterrupt(0x16);
y=_FLAGS&0x40;
if(y == 0) {
_AH=0x00;
x=_AL;
return x; }
return '?'; }
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng

15. Another definition of class Air
Attributes of air-plane:
size, and position.
Another definition of class Air
void main(void) {
int driver = DETECT,mode;
int i,k,f=0,f3=0;
char x;
Air y1, y2, y3;
initgraph(&driver,&mode,"a:\\bgi");
setcolor(WHITE);
line(1,400,400,400);
for ( i = 0; i < 80; i++ )
x=read_key();
if (x =='u') f=f-8;
if (x =='i') f=f+8;
setcolor(BLUE); y1.size=2;
y1.i=5*i; y1.k=f;
y1.planeshow(); /*y1.planeshow(5*i, f); */
delay (300);
y1.ereasep(); }
closegraph();
void Air::ereasep(int i, int k) {
int j;
setcolor(BLACK);
circle(i+5, 200+size+k, size);
circle(i+3, 200+2*size+k, size);
for (j=0; j<=4+3*size; j=j+1)
circle(i+j, 200+k, size);
circle(i+5, 200-size+k, size);
circle(i+3, 200-2*size+k, size); }
char read_key()
{ int y=1;
char x;
_AH=0x01;
geninterrupt(0x16);
y=_FLAGS&0x40;
if(y == 0)
_AH=0x00;
x=_AL;
return x; }
return '?';
#include <graphics.h>
#include<iostream.h>
#include<conio.h>
class Air{
public:
int size; /** the size of the air-plane **/
int i; /** the horizontal position **/
int k /** the vertical position **//
void planeshow();
void ereasep(); };
void Air::planeshow() {
int j;
circle(i+5, 200+size+k, size);
circle(i+3, 200+2*size+k, size);
for (j=0; j<=4+3*size; j=j+size)
circle(i+j, 200+k, size);
circle(i+5, 200-size+k, size);
#include<dos.h>
circle(i+3, 200-2*size+k, size); }
4/29/2019
CS3369 Real Time Control Software/Wang Lusheng