Thread: Question from a Noobie

This is my first here - i love this website. I have been teaching myself C and have a very beginner question that is probably easily answerable. Why does the following program give me garbage for the "long" type value? Will any other data type besides "float" work? Why not? Thanks in advance.

Code:

#include <stdio.h>
#include <stdlib.h>
int main(void)
{
    int yearsold;
    float floatsecondsold;
    long longsecondsold;
    printf("Please enter how many years old you are!\n");
    scanf("%d", yearsold);
    floatsecondsold=yearsold*3.156e7;
    longsecondsold=yearsold*3.156e7;
    printf("According to float, you are %f seconds old.  According to long, you are %f seconds old.\n", floatsecondsold, longsecondsold);
    return 0;
}

Thank you very much, but I swear something still fishy. See if you can figure out this one:

Code:

#include <stdio.h>
#include <stdlib.h>
int main(void)
{
    int quarts_water;
    int grams_of_water;
    float molecules_of_water;
    long longmolecules;
    printf("Please enter how many quarts of whater you have!\n");
    scanf("%d", &quarts_water);
    grams_of_water=quarts_water*950;
    molecules_of_water=grams_of_water/3e-23;
    longmolecules=grams_of_water/3e-23;
    printf("You have %f molecules of water, and according to long you have %ld molecules.\n", molecules_of_water, longmolecules);
    return 0;
}

When I run this program, I get garbage for the long printout. I'm having a hard time substituting different data types, basically.