Passing structures into functions in c [closed] - c

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I want to write a simple c code to create a garden structure,input details like num_animals, type of garden and size of garden.
However, my code is giving me some garbage output.
#include <stdio.h>
#include <string.h>
struct Garden
{
int num_animals;
int size;
char type[10];
};
void Input(struct Garden gardname)
{
printf("\nEnter number of animals\n");
scanf("%d",&gardname.num_animals);
printf("\nEnter size\n");
scanf("%d",&gardname.size);
printf("\nEnter type\n");
scanf("%s",gardname.type);
}
void Output(struct Garden gardname)
{
printf("Num of animals:%d\n",gardname.num_animals);
printf("size:%d\n",gardname.size);
printf("type:%s\n",gardname.type);
}
int main()
{
struct Garden Lumbini;
Input(Lumbini);
Output(Lumbini);
return 0;
}

Answer 1

The functions you have defined, by default use call by value method of passing arguments, which means that although you have Lumbini structure to which you intend to read and write elements, your functions will instead make a copy of Lumbini(in this case gardname), and write to, or print out that copy, not Lumbini. It may lead to duplicate values. I have written the same program using call by reference (note how a pointer to structure is the expected parameter in function, and the reference of lumbini is passed on call). This insures that there are no duplicates, and only the relevant structure (in this case, lumbini) is being manipulated.
#include <stdio.h>
#include <string.h>
struct Garden
{
int num_animals;
int size;
char an_type[10];
};
void Input(struct Garden *gardname)
{
printf("\nEnter number of animals\n");
scanf("%d", &gardname->num_animals);
printf("\nEnter size\n");
scanf("%d", &gardname->size);
printf("\nEnter type\n");
scanf("%s", gardname->an_type);
}
void Output(struct Garden *gardname)
{
printf("Num of animals:%d\n",gardname->num_animals);
printf("size:%d\n",gardname->size);
printf("type:%s\n",gardname->an_type);
}
int main()
{
struct Garden Lumbini;
Input(&Lumbini);
Output(&Lumbini);
return 0;
}
You are getting garbage values because gardname in Output function is a local variable to an uninitialized copy of lumbini structure. When you print out the values of gardname, they will be garbage values as they are not initialized. As the function finishes execution, gardname is destroyed.
Also, instead of writing
scanf("%d",&gardname.num_animals)
you must write
scanf("%d", &gardname->num_animals)
This will read into the address of pointer gardname plus the offset of member num_animals into the structure.