C++ Char array not working - c++

Question

I'm trying to get this program working, but get odd output. I know a char buffer is not ideal here, but it's for an assignment and not of my own design. Here's my code:
#include <iostream>
#include <string>
#include <cstring>
using namespace std;
//Place your class definition here
class student {
public:
void inputData(int a, char s[20], float e, float m, float sci);
void printData();
private:
int admno;
char sname[20];
float eng;
float math;
float science;
float total;
float ctotal();
};
int main () //This is your main driver. Do NOT make any changes to it
{
student obj ;
int a;
char s[20];
float e, m, sci;
cin >> a;
cin.getline(s,20);
cin.clear();
cin.ignore(10,'\n');
cin >> e;
cin >> m;
cin >> sci;
obj.inputData(a, s, e, m, sci);
obj.printData();
return 0;
}
//Place your class member function definitions here
void student::inputData(int a, char s[], float e, float m, float sci) {
admno = a;
*sname = *s;
eng = e;
math = m;
science = sci;
total = ctotal();
}
void student::printData() {
cout << "Admission number: " << admno << endl << "Student name: ";
for (int i = 0; i < 20; i++)
cout << sname[i];
cout << endl << "English: " << eng << endl << "Math: " << science << endl << "Science: " << science << endl << "Total: " << total;
}
float student::ctotal() {
return (eng + math + science);
}
Here's my input:
98745
Kyle Smith
98
78
62
Here's the expected output:
Admission number: 98745
Student name: Kyle Smith
English: 98
Math: 78
Science: 62
Total: 238
Here's the actual output:
Admission number: 98745
Student name:  m ╩`uÄM■Å■   ║k`u
English: 98
Math: 62
Science: 62
Total: 238
Please give advice on how to fix. I have to stick with that char buffer, but don't know why I'm getting this corruption.
Thanks!

Answer 1

*sname = *s;
This copies one character, not the entire string. If you want to copy the entire string, you need to use std::strcpy
std::strcpy(sname, s);
or a loop
char* src = s;
char* dst = sname;
while (src) {
*dst = *src;
++src;
++dst;
}
Of course, you could do away with all of this manual string handling and use std::string instead:
//Place your class definition here
class student {
public:
void inputData(int a, std::string s, float e, float m, float sci);
void printData();
private:
int admno;
std::string sname;
float eng;
float math;
float science;
float total;
float ctotal();
};
void student::inputData(int a, std::string s, float e, float m, float sci) {
admno = a;
sname = std::move(s);
eng = e;
math = m;
science = sci;
total = ctotal();
}

Answer 2

Here is what happening:
cin >> a;
cin.getline(s,20);
cin.clear(); // never mind this, doesn't do anything in this context
cin.ignore(10,'\n');
Your int is read and stored in a
cin now contains \n left over after you pressed Enter
getline immediately attempts to read it into s but it discards it, s is now empty, but getline operation is complete.
Why does it still wait for the input of the name? Because cin.ignore is waiting for \n or at least 10 chars to be entered, but the stream buffer is now empty.
You enter your name and press Enter, ignore at least gets its \n and is now complete but your entered string is not stored anywhere. It is just ignored. If it wasn't ignored you would have gotten the 1st char of this string in the output, but you haven't.
Long story short, your input is broken. You should clear that \n after you entered the first number before getline. Only then, after you have your name stored in s you can attempt to pass it to the function, there is no point in passing a pointer to empty array and expecting it to work.