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  Value and type of last evaluated expression: Address of array element: Address of array elementx:  (none)

The pointer e inside move_ellipse() points to ellie inside main().

The pointer e inside calculate_area() points to ellie inside main() as it was passed the value by the calling function.

The pointer el inside read_ellipse() points to ellie inside main() so el->member refers to ellie.member.

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Code

 Header...

#define PI 3.14159265358979
typedef struct ellipse {
  float centre[2];
  float axes[2];
  float orientation;
  float area;
}Ellipse;

void calculate_area (Ellipse *el);
void read_ellipse (Ellipse *el);
void resize_ellipse (Ellipse *el,float scale);
void move_ellipse (Ellipse *el,float dx[2]);


 int main(){
»  Ellipse ellie;
»  float moveby[2], resize;

»  printf("Welcome to the ellipse program\n");
»  read_ellipse(&ellie);

»  printf("The area of the ellipse is: %f\n", ellie.area);

»  printf("Amount to move the ellipse?\n");
»  scanf("%g %g", &moveby0, &moveby1);
  
»  move_ellipse(&ellie, moveby);

»  printf("Amount to resize the ellipse?\n");
»  scanf("%g", &resize);
  
»  resize_ellipse(&ellie, resize);

»  return 0;
}
 ... 


 void read_ellipse(Ellipse *el){

»  printf("Centre? (x,y)\n");
»  scanf("%f %f", &el->centre[0], &el->centre[1]);

»  printf("Length of axes ( > 0 )?\n");
»  scanf("%f %f", &el->axes[0], &el->axes[1]);

»  printf("Orientation to the vertical?\n");
»  scanf("%f", &el->orientation);

»  calculate_area(el);// Pass the pointer to another function
}
 ... 


 void resize_ellipse(Ellipse *el,float scale){
»  el->axes0*=scale;
»  el->axes1*=scale;
»  calculate_area(el);
}
 ... 


 void calculate_area(Ellipse *e){
»  e->area=PI*e->axes[0]*e->axes[1];
}
 ... 


 void move_ellipse(Ellipse *el,float dx[2]){
»  el->centre0+=dx0;
»  el->centre1+=dx1;
}
 ...
Memory

calculate_area()

128
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e = 228

calculate_area()

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e = 228

read_ellipse()

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el = 228

move_ellipse()

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el = 228
dx = 220

resize_ellipse()

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el = 228
scale = 3.79999995

main()

216
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resize = 2.38714847e+28
moveby[0] = -1.58221e+25
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moveby[1] = 7.027e-08
ellie.centre[0] = -1.48217e+17
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ellie.centre[1] = -4.49525e+33
ellie.axes[0] = 5.05323e-20
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ellie.axes[1] = 1.37825e-11
ellie.orientation = 2.06185038e+24
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ellie.area = -2.54576014e-25

NB: the actual memory address of each variable is the
address shown plus 4290828144 (0xFFC0D770).

.

Input was:

7.2 4.5 1.2  4.3 1.7
1.1 2.2 3.8

Show output (Before looking at the output, work out what you think it put should be and see if you are right.)

Output

Welcome to the ellipse program
Centre? (x,y)
Length of axes ( > 0 )?
Orientation to the vertical?
The area of the ellipse is: 16.210619
Amount to move the ellipse?
Amount to resize the ellipse?
                                                                                                                                                                                                                                                                       
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