How to add more than one user input to an array?

Question

How can I add more than one string or user input to an array? I am trying to create a contact book that requires the user to add up to 10 contacts. I am trying to store them an an array or a txt file and then later I want to be able to use this input.

Here is my code. If what I'm trying to say is not clear, running the code will help.

#include <cstdlib>
#include <iostream>
#include <fstream>

using namespace std;

int main(int argc, char *argv[])
{
    // declare two variables;
    char name[20];
    int age;
string ans;
do {    
    // get user to input these;
    cout << "What is your name: ";
    cin >> name;
    cout << "What is your age : ";
    cin >> age;
    cout<<"continue ";cin>>ans;
  }while((ans == "y" || ans=="yes"));  
    // create output stream object for new file and call it fout
    // use this to output data to the file "test.txt"
    char filename[] = "test.txt";
    ofstream fout(filename);
    fout << name << "," << age << "\n";    // name, age to file
    fout.close();   // close file

    // output name and age : as originally entered
    cout << "\n--------------------------------------------------------"
         << "\n name and age data as entered";
    cout << "\n    Your name is: " << name;
    cout << "\n    and your age is: " << age;     

    // output name and age : as taken from file           

    // first display the header
    cout << "\n--------------------------------------------------------"
         << "\n name and age data from file"
         << "\n--------------------------------------------------------";   

      ifstream fin(filename);

       char line[50];               
    fin.getline(line, 50);      


    char fname[20];     
    int count = 0;       
    do
    {
        fname[count] = line[count];       
        count++;
    }
    while (line[count] != ',');        
    fname[count] = '\0';              


    count++;
    char fage_ch[10];    
    int fage_count = 0;   
    do
    {
        fage_ch[fage_count] = line[count];   
        fage_count++; count++;               
    }
    while (line[count] != '\0');             
    fage_ch[fage_count] = '\0';


    int fage_int = 0;        
    int total = 0;           
    char temp;               

    for (int i = 0; i < (fage_count); i++)
    {
        temp = fage_ch[i];
        total = 10*total + atoi(&temp);
    }

    fage_int = total;

    // display data
    cout << "\n\n    Your name is: " << fname;
    cout << "\n    and your age is: " << fage_int;
    cout << "\n\n--------------------------------------------------------";    

      cout <<endl;

    return EXIT_SUCCESS;
}

Is there a reason to use a file? Or it's just the way you tried? I try to understand what you want to do. — George Kastrinis
– George Kastrinis, Commented Oct 21, 2011 at 23:16

Terhands · Accepted Answer · 2011-10-21 22:11:09Z

You would probably be better off using an array of structs instead of two seperate arrays to store the name & age for each entry. Then you can just loop through using strcpy to copy the input string from name into your struct's name. If you aren't comfortable with structs you could also use a couple of 2 dimensional arrays.

This looks like a homework assignment so I'm not going to post code, but for a basic algorithm to get you started (and hopefully simplify what you've got):

#define MAX_CONTACTS 10
#define MAX_NAME_LENGTH 20

// 2D array to store up to 10 names of max 20 character length
char nameVar[MAX_CONTACTS][MAX_NAME_LENGTH]
int ageVar[MAX_CONTACTS]

do until end of user input
    read name into nameVar[index]
    read age into ageVar[index]
    index += 1
end loop

while contactCounter < index
    ouput nameVar[contactCounter]
    output age[contactCounter]
    // you could also write to file in this loop if thats what you're trying to do
    // using the fprintf function to write to an opened file
    contactCounter += 1
end loop

Also, I'm not sure what you're trying to do with that atoi call, but it looks like it shouldn't be necessary. How atoi works is that it looks at the first character it is passed and it converts all of the digits until it encounters a non-digit character in the array. So if you have the char array c="123h" atoi would return 123. If you pass atoi "1h2" it will return 1.

Also you can use fprintf to print out both a char array and an int to a file.

So if you've got int i and char s[10] = "hello" and file stream you could print to stream like:

fprintf(stream, "my text to display: %s %i", s,i)

I hope that helps.

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