Structures - C Programming - Union - Basic Programming

• Write a C program to add two distances (in inch-feet system) using
Structures
• Structure name is Distance
• Two members – feet as integer, inch as float
• Three structure variables - d1,d2,result
• Get d1 and d2 from the user. Then add and get the result
• Convert inches to feet if it is greater than or equal to 12
• Print the final result

#include <stdio.h>
struct Distance {
int feet;
float inch;
} d1, d2, result;
int main() {
// take first distance input
printf("Enter 1st distancen");
printf("Enter feet: ");
scanf("%d", &d1.feet);
printf("Enter inch: ");
scanf("%f", &d1.inch);
// take second distance input
printf("nEnter 2nd distancen");
printf("Enter feet: ");
scanf("%d", &d2.feet);
printf("Enter inch: ");
scanf("%f", &d2.inch);
// adding distances
result.feet = d1.feet + d2.feet;
result.inch = d1.inch + d2.inch;
// convert inches to feet if greater than 12
while (result.inch >= 12.0) {
result.inch = result.inch - 12.0;
++result.feet;
}
printf("nSum of distances = %d'-%.1f"", result.feet,
result.inch);
return 0;
}

Passing structs to functions
#include <stdio.h>
struct student {
char name[50];
int age;
};
// function prototype
void display(struct student s);
int main() {
struct student s1;
printf("Enter name: ");
gets(s1.name);
printf("Enter age: ");
scanf("%d", &s1.age);
display(s1); // passing struct as an argument
return 0;
}
void display(struct student s) {
printf("nDisplaying informationn");
printf("Name: %s", s.name);
printf("nAge: %d", s.age);
}

Return struct from a function
#include <stdio.h>
struct student
{
char name[50];
int age;
};
// function prototype
struct student getInformation();
struct student getInformation()
{
struct student s1;
printf("Enter name: ");
gets(s1.name);
printf("Enter age: ");
scanf("%d", &s1.age);
return s1;
}
int main()
{
struct student s;
s = getInformation();
printf("nDisplaying informationn");
printf("Name: %s", s.name);
printf("nRoll: %d", s.age);
return 0;
}

Passing struct by reference – Example
1
#include <stdio.h>
typedef struct Complex
{
float real;
float imag;
} complex;
void addNumbers(complex c1,
complex c2, complex *result);
int main()
{
complex c1, c2, result;
printf("For first number,n");
printf("Enter real part: ");
scanf("%f", &c1.real);
printf("Enter imaginary part: ");
scanf("%f", &c1.imag);
printf("For second number, n");
printf("Enter real part: ");
scanf("%f", &c2.real);
printf("Enter imaginary part: ");
scanf("%f", &c2.imag);
addNumbers(c1, c2, &result);
printf("nresult.real = %.1fn", result.real);
printf("result.imag = %.1f", result.imag);
return 0;
}
void addNumbers(complex c1, complex c2,
complex *result)
{
result->real = c1.real + c2.real;
result->imag = c1.imag + c2.imag;
}

Passing struct by reference – Example
2

Union
• Only store information in one field at any one time
• When a new value is assigned to a field, existing data is replaced with
the new data.
• Thus unions are used to save memory.
• They are useful for applications that involve multiple members, where
values need not be assigned to all the members at any one time.

Declaration & initialization of union
• Like structures, an union can be declared with the keyword union
union student
{
int marks;
char gender;
};
• To access the members of the union, use the dot operator (.)

Declaration &
initialization of
union
• Unlike structures, initialization cannot be done to all members together.
#include <stdio.h>
typedef struct point1
{
int x,y;
};
typedef union point2
{
int x;
int y;
};
main()
{
point1 p1={2,3};
// point p2={4,5}; illegal with union
point2 p2;
p2.x=4;
p2.y=5;
printf(“The coordinates of p1 are % and %d”, p1.x,p1.y);
printf(“The coordinates of p2 are % and %d”, p2.x,p2.y);
}

Wrong output
• Output
The coordinated of p1 are 2 and 3
The coordinated of p2 are 5 and 5

//Corrected program
#include <stdio.h>
struct point1
{
int x,y;
};
union point2
{
int x,y;
};
main()
{
struct point1 p1={2,3};
// point p2={4,5}; illegal with union
union point2 p2;
p2.x=4;
printf("The coordinates of p1 are %d and %d n", p1.x,p1.y);
printf("The x coordinates of p2 is %d n", p2.x);
p2.y=5;
printf("The y coordinates of p2 is %d", p2.y);
}

Correct output
• Output:
The coordinates of p1 are 2 and 3
The x coordinates of p2 are 4
The y coordinates of p2 are 5

Another example
#include <stdio.h>
#include <string.h>
union Data {
int i;
float f;
char str[20];
};
int main( ) {
union Data data;
data.i = 10;
printf( "data.i : %dn", data.i);
data.f = 220.5;
printf( "data.f : %fn", data.f);
strcpy( data.str, "C Programming");
printf( "data.str : %sn", data.str);
return 0;
}

Difference between structure & union

Structures - C Programming - Union - Basic Programming

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