Printing structures using loop - c

Question

How to print structure contents using for-loop? If pointers, how to assign pointer to structure? I have attached code that I made that makes a structure using data that user inputs, and prints them out in an orderly fashion. My problem is that you have to write a lot of printf() and gets_s() statements to receive and print input. I feel like it would be easier to do this using a for-loop. I tried to make a for-loop as you can see in the code using pointers, but it doesn't compile, and I'm pretty sure that it is the wrong way to assign pointers to structures.
TL;DR: How to print structure contents using for-loop? If pointers, how to assign pointer to structure?
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <conio.h>
#define maxName 50
#define maxNation 50
#define maxAge 100
struct astronaut
{
char firstName[maxName];
char lastName[maxName];
char nation[maxNation];
int age = 0;
char missionName[maxAge];
int missionYear[50];
};
int main()
{
int i = 0;
struct astronaut candidate1;
struct astronaut candidate2;
struct astronaut candidate3;
struct astronaut mission1;
struct astronaut mission2;
struct astronaut mission3;
printf("Please enter the first name of the candidate: ");
gets_s(candidate1.firstName);
printf("Please enter the last name of the candidate: ");
gets_s(candidate1.lastName);
printf("Please enter the nationality of the candidate: ");
gets_s(candidate1.nation);
printf("Please enter the age of the candidate: ");
scanf("%d", &candidate1.age);
printf("Please enter the first name of the candidate: ");
gets_s(candidate2.firstName);
printf("Please enter the last name of the candidate: ");
gets_s(candidate2.lastName);
printf("Please enter the nationality of the candidate: ");
gets_s(candidate2.nation);
printf("Please enter the age of the candidate: ");
scanf("%d", &candidate2.age);
printf("Please enter the first name of the candidate: ");
gets_s(candidate3.firstName);
printf("Please enter the last name of the candidate: ");
gets_s(candidate3.lastName);
printf("Please enter the nationality of the candidate: ");
gets_s(candidate3.nation);
printf("Please enter the age of the candidate: ");
scanf("%d", &candidate3.age);
printf("Enter a Mission Name: ");
gets_s(mission1.missionName);
printf("Enter the year the mission was conducted: ");
scanf("%d", &mission1.missionYear);
printf("Enter a Mission Name: ");
gets_s(mission2.missionName);
printf("Enter the year the mission was conducted: ");
scanf("%d", &mission2.missionYear);
printf("Enter a Mission Name: ");
gets_s(mission3.missionName);
printf("Enter the year the mission was conducted: ");
scanf("%d", &mission3.missionYear);
struct astronaut *ptr;
struct candidate *ptr;
// printf("\n\tAstronaut Candidate Database\n");
// printf("Name: %s %s \t Age: %d \t Nationality: %s\n", candidate1.firstName, candidate1.lastName, candidate1.age, candidate1.nation);
// printf("Name: %s %s \t Age: %d \t Nationality: %s\n", candidate2.firstName, candidate2.lastName, candidate2.age, candidate2.nation);
// printf("Name: %s %s \t Age: %d \t Nationality: %s\n", candidate3.firstName, candidate3.lastName, candidate3.age, candidate3.nation);
// printf("\n\tAstronaut Mission Database\n");
// printf("Mission Name: %s \t Year: %d\n", mission1.missionName, mission1.missionYear);
// printf("Mission Name: %s \t Year: %d\n", mission2.missionName, mission2.missionYear);
// printf("Mission Name: %s \t Year: %d\n", mission3.missionName, mission3.missionYear);
for (int index = 0; index < 5; index++)
{
printf("Name: %s %s \t Age: %d \t Nationality: %s\n", *ptr.firstName, *ptr.lastName, *ptr.age, *ptr.nation);
ptr++;
}
_getch();
return 0;
}

Answer 1

I think you need 2 structs. An astronaut and a mission aren't the same thing. As it is now, you have several unused fields depending on whether you're entering data for an astronaut or a mission. You could do something like this:
#include <stdio.h>
#define maxName 50
#define maxNation 50
#define maxAge 100
struct astronaut
{
char firstName[maxName];
char lastName[maxName];
char nation[maxNation];
int age;
};
struct mission
{
char missionName[maxAge];
int missionYear; // why do you have an array of 50 ints for the missionYear?
};
void enter_candidate_data(struct candidate* cand)
{
// not famliar with gets_s .. I would use fgets here, you can read the manpage on that if you desire
printf("Please enter the first name of the candidate: ");
gets_s(cand->firstName);
printf("Please enter the last name of the candidate: ");
gets_s(cand->lastName);
printf("Please enter the nationality of the candidate: ");
gets_s(cand->nation);
printf("Please enter the age of the candidate: ");
scanf("%d", &(cand->age));
}
void enter_mission_data(struct mission* mis)
{
printf("Enter a Mission Name: ");
gets_s(mis->missionName);
printf("Enter the year the mission was conducted: ");
scanf("%d", &(mis->missionYear));
}
int main()
{
int i;
struct astronaut candidates[3];
struct mission missions[3];
for (i=0; i<3; i++)
{
enter_candidate_data(&(candidates[i]));
// you can put this in a separate loop if you want to enter all
// candidate data first
enter_mission_data(&(missions[i]));
}
// you could also write functions to print the data instead, depends on
// how you want it all presented
for (int i=0; i<3; i++)
{
printf("Name: %s %s \t Age: %d \t Nationality: %s\n",
candidates[i].firstName, candidates[i].lastName, candidates[i].nation);
printf("Mission Name: %s, year %d\n", missions[i].missionName,
missions[i].missionYear);
}
return 0;
}
You may want a number of missions (or even just one) associated with a particular astronaut. If so, I would define the data structures like this
#define MAX_ASTRONAUT_MISSIONS 20
struct mission
{
char missionName[maxAge];
int missionYear;
};
struct astronaut
{
char firstName[maxName];
char lastName[maxName];
char nation[maxNation];
int age;
struct mission missions[MAX_ASTRONAUT_MISSIONS];
};
This will allow you to associate MAX_ASTRONAUT_MISSION missions with each astronaut. Or, more realistically, a single mission could be associated with several astronauts. In that case, you may want data structures more like this
struct mission
{
char missionName[maxAge];
int missionYear;
};
struct astronaut
{
char firstName[maxName];
char lastName[maxName];
char nation[maxNation];
int age;
// using a pointer to missions will allow you to create one mission, and
// all the astronauts on that mission could get a pointer to it,
// designating they were all on that singular mission.
struct mission* missions[MAX_ASTRONAUT_MISSIONS];
};