help with reading a structure

Code:

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#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>

#define MAX 20

typedef struct
    {
        int    ID;
        char*  firstname;
        char  lastname[MAX];
        float  unit;
        double gradeAvg;
    }INFO;

int main (void)
{
    // Global declarations
      INFO myInfo;
    int i = 0;

    // Statements
        myInfo.firstname = (char*)calloc(20,sizeof(char));
        printf("Enter your first and last name:\n");
    for(i = 0; i < MAX; i++)
    {
            scanf("%s %c", myInfo.firstname, &myInfo.lastname[i]);
    }


    printf("Enter your ID number:\n");
    scanf("%d", &myInfo.ID);
    printf("Enter your total unit completed:\n");
    scanf("%f",&myInfo.unit);
    printf("Enter your grade point average:\n");
    scanf("%lf", &myInfo.gradeAvg);

    i = 0;
    for(i = 0; i < MAX; i++)
    {
      printf("%9s %c\n", *myInfo.firstname, myInfo. lastname[i]);
    }
    printf("%6d\n", myInfo.ID);
    printf("%.1f\n",myInfo.unit);
    printf("%lf\n", myInfo.gradeAvg);

    return 0;
}

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can i get a little help on correctting the loop over scanf
thank you

Whoa! What are you doing in your struct definition? You've got the firstname element defined as a pointer to a character- that only guarantees you've got room for that one character.

You want both firstname and lastname to be strings (ie. arrays of characters) right? Well, declare them in your struct to be that, and then scanf them as strings. You shouldn't need a loop at all.

well my instructor ask to dynamically allocate the firstname though
so shouldn't it be pointer to char ?

Quote:

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Originally Posted by khoavo123

well my instructor ask to dynamically allocate the firstname though
so shouldn't it be pointer to char ?

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Yes. That part is fine though slightly pointless when you're just going to make it 20 characters large anyway. Plus, you need to free what you calloc.

Why exactly are you looping from 0 to MAX? Are you aware that myInfo is not an array?

Yes, you're right. I didn't see the calloc. What that does is make firstname a pointer to a continuous block of memory, the size of twenty chars. It makes it an array of characters and it's no different than if you'd declared it the same way as lastname.

You still shouldn't need a loop for the lastname. You can read that in all in one go, just the same as firstname. What the loop is making me do is type in my entire first name 20 times and then individual characters in my last name. So if my name is Joseph Bloggs I have to do this:

Code:

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Joseph B
Joseph l
Joseph o
Joseph g

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and so on.

so after i make changes to this

Code:

---

#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>

#define MAX 20

typedef struct
    {
        int    ID;
        char*  firstname;
        char  lastname[MAX];
        float  unit;
        double gradeAvg;
    }INFO;

int main (void)
{
    // Global declarations
      INFO myInfo;


    // Statements
    myInfo.firstname = (char*)calloc(20,sizeof(char));

    printf("Enter your first and last name:\n");
    scanf("%s %s", myInfo.firstname, &myInfo.lastname);
    printf("Enter your ID number:\n");
    scanf("%d", &myInfo.ID);
    printf("Enter your total unit completed:\n");
    scanf("%f",&myInfo.unit);
    printf("Enter your grade point average:\n");
    scanf("%lf", &myInfo.gradeAvg);



    printf("%9s %19s\n", *myInfo.firstname, myInfo. lastname);
    printf("%6d\n", myInfo.ID);
    printf("%.1f\n",myInfo.unit);
    printf("%lf\n", myInfo.gradeAvg);

    system("PAUSE");
    return 0;
}

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the program has no problem input data but it cannot printout data

This is wrong:

Code:

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scanf("%s %s", myInfo.firstname, &myInfo.lastname);

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It should be:

Code:

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scanf("%s %s", myInfo.firstname, myInfo.lastname);

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(but then this leaves you vulnerable to buffer overflow)