Thread: if any student is named Jackson, help please

Hi

The code below is incomplete but still you can run it. There is some problem with it. When I have entered student #1's data it cycles through the loop automatically without asking for any data input. Please help me to solve the problem. Thanks.

Code:

// if_any_student_named_jackson_heights.cpp
// check if any student is named Jackson Heights

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <iomanip>

using namespace std;

struct Student {char name[16]; int rollno; string sex; int age; float marks;};

const int N = 5;

Student stud[N];

int main()
{

        int i;

        cout << "enter the students' details below\n\n";

        for (i=0; i<N; i++)
        {
                cout << "enter student #" << (i+1) << "\'s name: ";
                cin.get(stud[i].name, 16);
                cout << "enter roll no.: ";
                cin >> stud[i].rollno;
                cout << "enter sex: ";
                cin >> stud[i].sex;
                cout << "enter age: ";
                cin >> stud[i].age;
                cout << "enter marks: ";
                cin >> stud[i].marks;
        }


        system("pause");
        return 0;

}

Do not use char, and do not use std::cin.get for strings. Use std::string and std::getline.

Thank you, rags_to_riches, Elysia.

@ Elysia: The problem is I have to use C-strings because this is what I'm being taught

Okay. I think I have solved the problem in the code in my first post above. Now I face another problem. Please have a look on the output below. It should be "#2" instead. Where am I going wrong? Please help me. Thanks.

Code:

// if_any_student_named_jackson_heights.cpp
// check if any student is named Jackson Heights

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <iomanip>

using namespace std;

struct Student {char name[16]; int rollno; string sex; int age; float marks;};

const int N = 2;

Student stud[N];

int main()
{

        int i; char name_search[20];

        cout << "enter the students' details below\n\n";

        for (i=0; i<N; i++)
        {
                cout << "\nenter student #" << (i+1) << "\'s name: ";
                cin.get(stud[i].name, 16);
                cout << "enter roll no.: ";
                cin >> stud[i].rollno;
                cout << "enter sex: ";
                cin >> stud[i].sex;
                cout << "enter age: ";
                cin >> stud[i].age;
                cout << "enter marks: ";
                cin >> stud[i].marks;
                cin.ignore();
        }

        cout << "\n\nenter the name to be searched for: ";
        cin.get(name_search, 20);

        for (i=0; i<N; i++)
        {
                if (stud[i].name == name_search)
                {
                        break;
                }
        }

        cout << "the student at #" << (i+1) << " in the record"
             << " matches the entered name\n\n";


        system("pause");
        return 0;

}

OUTPUT

Code:

enter the students' details below


enter student #1's name: jackson
enter roll no.: 1
enter sex: male
enter age: 18
enter marks: 99

enter student #2's name: heights
enter roll no.: 2
enter sex: male
enter age: 19
enter marks: 100


enter the name to be searched for: heights

the student at #3 in the record matches the entered name

Press any key to continue . . .

You have to use strcmp to compare c strings. I would recommend you use c++ strings. Even if your teacher doesn't accept them, it's still good training.

Originally Posted by Elysia

You have to use strcmp to compare c strings. I would reccomend you use c++ strings. Even if your teacher doesn't accept them, it's still good training.

Thanks for the reply.

If the teacher doesn't like then he will simply cross it!

Isn't this possible to correct that "#3" issue without using strcomp function? I don't understand why the code generates, for example, "#3" instead of "#2". Please help me.

Originally Posted by jackson6612

If the teacher doesn't like then he will simply cross it!

Well, like I said, it never hurts to try. And even if the teacher doesn't like it, you can make two versions, if only to familiarize yourself with C++ strings. You don't need to turn it in.

Isn't this possible to correct that "#3" issue without using strcomp function? I don't understand why the code generates, for example, "#3" instead of "#2". Please help me.

No. You are comparing two pointers, which would return equal iff the two were the exact same pointer. But you can have, for example, two strings not in the same memory location but with exactly the same contents.

Originally Posted by jackson6612

Isn't this possible to correct that "#3" issue without using strcomp function?

You could write your own function that does the same thing. Otherwise, no. And the function is called strcmp().

Thanks a lot, everyone.

I have modified the original to make it work. But there is a point I couldn't understand.

Code:

if (strcmp(stud[i].name,name_search)==0)

The if block is executed when the condition is evaluated to be true, that is "1" and "0" for false (the condition expression inside the parentheses is converted to bool type). So, why is "0" used above in the if condition expression for strcmp? Please let me know. Thanks.

This has nothing to do with true or false. strcmp returns one of three different values: < 0, 0 and > 0. Check the manual for strcmp.

Originally Posted by Elysia

This has nothing to do with true or false. strcmp returns one of three different values: < 0, 0 and > 0. Check the manual for strcmp.

Thank, Elysia.

I believe when it returns 0 it means the compared strings are the the same. What do other values, < 0 and > 0, mean? Please let me know. Thanks.

Did you read the documentation?

Nope. Sorry.

I have a class in next 5 mins and there is still so much to do!

You should always consult the documentation for something you don't understand.
If you don't understand the documentation, then that is understandable, and then you have every right to ask a question about what you don't understand.
But until then, I suggest you read the documentation. It's good training, and an essential skill.