File reading and writing in c++

Question

#include<iostream> #include<fstream> using namespace std; int main() { ofstream fout("student",ios::out); char name[30],ch; float marks=0.0; for(int i=0;i<5;i++) { cout<<"Stud"<<(i+1)<<":\tName"; cin.get(name,30); cout<<"\tMarks"; cin>>marks; cin.get(ch); fout<<name<<'\n'<<marks<<'\n'; } fout.close(); ifstream fin("student",ios::in); fin.seekg(0); cout<<"\n"; for(int i=0;i<5;i++) { fin.get(name,30); fin.get(ch); fin>>marks; fin.get(ch); cout<<name<<marks; } fin.close(); }

Now, there are two things I don't understand..why do you need cin.get(ch) while writing to the file(My textbook says to clear the input buffer). How does it help in doing so? I don't have much knowledge about the clearing of a buffer and How does it affect the following iterations?

Further, what if I don't separate the name and marks while writing to the file with a '\n'? And, while reading I read it like

fin>>get(name,30); fin>>marks;

Upon running the program I noticed that only the first iteration's values are being repeated 5 times. Why is this so?

VolAnd · Accepted Answer · 2015-12-25 07:58:23Z

Let's consider the following two lines

 cin >> marks; cin.get(ch);

In the condition when marks is a char. Because input from cin with >>operator requires pressing Enter from user, code of Enter-key ('\n') will be also in the input buffer.

If you do not remove this '\n' from input buffer, at the next iteration of your loop cin.get(name,30); will read this single character to name.

It was an example for cases when marks is a char.

In case of incorrect input, e.g. user inputs

 4vv6s5

as a mark (and marks variable is of float type) 4 will be taken to marks, and "vv6s5" to name of next student.

So a better way for cleaning input buffer after input can be as follows:

cin >> marks; do{ cin.get(ch); } while(ch != '\n');

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