while loop, really don't understand - c++

Question

hi im trying to do a while loop, im new to programming and reading online i cant really get my head around it, i have used flag to show that the inputted name matches the name in the data file, i want to do this so that after i know it doesnt match it loops it the whole thing again, i have no clue how to implement this,
{
clrscr();
cout << "This Is The Option To Delete A Record\n";
char yesno;
char search;
char name[21];
int flag = 0;
cout << "Enter Employee Name : ";
Input(name,20);
for (int r=0;r<row;r++)
{
if( strnicmp(name, emp[r].first_name, strlen(name) ) == 0 )
{
flag = 1;
clrscr();
cout << "Employee Number - " << emp[r].employee_number << endl;
cout << "Name - " << emp[r].first_name << " " << emp[r].surname << endl;
cout << "Department Number - " << emp[r].department_number << endl;
cout << "Week Ending Date - " << emp[r].weekend << endl;
cout << "Delete This Record (Y/N)? : ";
Input(yesno);
yesno = tolower(yesno);
if ( yesno == 'y' )
{
emp[r].deleted = true;
cout << "Record Has Been Deleted";
}
else if ( yesno == 'n')
{
cout << "Record Hasn't Been Deleted";
}
}
}
if (flag == 0)
{
cout << "There Are No Matching Records" << endl;
}
pressKey();
}

Answer 1

It's pretty simple, so have a bunch of code you want to keep executing it while a flag is zero, so that's just
int flag = 0;
while (flag == 0)
{
// whole bunch of code
}
That's it, just replace 'whole bunch of code' with the code you've written above.

Answer 2

Implementing this in a while loop would look like this:
bool flag=false;
while(!flag){
...
if(<find a match>) flag=true;
}

Answer 3

Assuming you understand the for loop, I think you can understand the while loop quite easily based on the comparison of for and while.
See, you used a for loop:
for (int r=0;r<row;r++){
// do stuff
}
There are 3 key points here.
int r=0 This is your initial condition.
r<row This is your condition which keeps the loop running.
r++ This is what happens at the end of each iteration of loop.
To rephrase the statements above:
Considering r equals zero initially, while r is less than row, increment r.
Now we can easily see how while loop is striking us:) To implement this, consider the following while loop example:
int r=0; //(1)
while(r<row){ //(2)
//do stuff
r++; //(3)
}
See, now the 2 loops do practically the same thing.
If you want to do operations based on a flag, you can also prefer an infinite loop:
while(1==1){
if(some condition)
break;
}
as well as an infinite for loop:
for(;;){
if(if some condition)
break;
}
Again, 2 loops are practically the same.

Answer 4

so basically, you have a file with some data. And also, you accept some data from the user.
And then you perform a comparison between the appropriate fields of the two sets.
Why would you want to do it all over again once the entire comparison (file process) is done?
if you simply want to run an infinite loop, you can do this:
while(true)
{
//your code
}
you can do same with a for loop also. infact for loop and while loop both are same except for the syntax. i.e. an infinite for loop.
for (int r=0;r<row;r++)
{
if(r==row-1)
{
r=0;
}
}
I guess what you want to do is to, once one set of user input doesn't match the file content, you want to take another set and match it again and so on.
so you don't need an infinite or always executing loop for this.
Just make your comparison module a separate function which should accept the set of user inputs. All you do is accept user inputs and show the result. And give the user an option to re-enter inputs.
Below is simple algo for what you want.
int main()
{
char a='a';
while(a != '~')
{
TakeUserInput();
if(PerformComparison())
{
cout << "Success";
break;
}
}
}
inside TakeUserInput() you do all those cin << to set a global array or set of global variable. also, you cin << a, to terminate program at your will.
and inside PerformComparison(), you do what you have posted here in your question.