C++ Programming, Cannot understand errors - c++

Question

I am a beginner at c++ programming, and this is only my second program. I am getting a consistent error of "expected unqualified-id before..." idk what it means and cannot solve it. This is on lines 21,27,29,33,35,38,40,43,45.48,54,56,59,61,64,66,70.
#include <cstdlib>
#include <iostream>
#include <fstream>
#include <math.h>
using namespace std;
int main ();
int a, b, c, x,y;
int discriminant;
double x1, x2;
int countdataisinvalid=0;
int countdataisvalid=0;
int countnolastterm=0;
int countonexvalue=0;
int countnomiddleterm=0;
int counttwoxterms=0;
while(!cin.eof)
{
a*x*x+b*x+c;
}
if (a==0),
countdataisinvalid++;
{
cout << "A is 0, data invalid." << endl;
}
else if, (discriminant < 0),
countdataisinvalid++;
{
cout << "The square is a negative number, data invalid." << endl;
}
else,
countdataisvalid++;
{
cout << " Data set is valid." << endl;
}
if (c==0),
countnolastterm++;
{
cout << "C is 0, there is no last term." << endl;
}
{
x1 = (-b + sqrt(b*b-4*a*c))/(2*a);
x2 = (-b - sqrt(b*b-4*a*c))/(2*a);
cout.precision(3);
}
if (x1==x2),
countonexvalue++;
{
cout << "Only one x value." << endl;
}
else, if (x1==-x2),
countnomiddleterm++;
{
cout << "There is no middle term." << endl;
}
else
counttwoxterms++;
{
cout << "There are two x values." << endl;
}
{
y = a*x1*x1+b*x1+c
y = a*x2*x2+b*x2+c
cout << "When x is " << x << "y is " << y << endl;
}

Answer 1

Your code contains too many errors. You should learn C++ again with writing simple programs.
At least this code compiles.
#include <cstdlib>
#include <iostream>
#include <fstream>
#include <math.h>
using namespace std;
int main ()
{ // use { to begin definition of function, not ;
// initialize ariables for in case the reading fails
int a = 0, b = 0, c = 0, x = 0, y = 0;
int discriminant = 0;
double x1 = 0, x2 = 0;
int countdataisinvalid=0;
int countdataisvalid=0;
int countnolastterm=0;
int countonexvalue=0;
int countnomiddleterm=0;
int counttwoxterms=0;
// you should read numbers instead of writing possibly infinite loop and meaningless statement
cin >> a >> b >> c >> x >> discriminant >> x1 >> x2;
if (a==0) // remove extra comma
{
countdataisinvalid++; // move this statement to right position
cout << "A is 0, data invalid." << endl;
}
else if (discriminant < 0) // remove extra commas
{
countdataisinvalid++; // move this statement to right position
cout << "The square is a negative number, data invalid." << endl;
}
else // remove extra comma
{
countdataisvalid++; // move this statement to right position
cout << " Data set is valid." << endl;
}
if (c==0) // remove extra comma
{
countnolastterm++; // move this statement to right position
cout << "C is 0, there is no last term." << endl;
}
{
x1 = (-b + sqrt(b*b-4*a*c))/(2*a);
x2 = (-b - sqrt(b*b-4*a*c))/(2*a);
cout.precision(3);
}
if (x1==x2) // remove extra comma
{
countonexvalue++; // move this statement to right position
cout << "Only one x value." << endl;
}
else if (x1==-x2) // remove extra commas
{
countnomiddleterm++; // move this statement to right position
cout << "There is no middle term." << endl;
}
else
{
counttwoxterms++; // move this statement to right position
cout << "There are two x values." << endl;
}
{
y = a*x2*x2+b*x2+c; // add semicolon and remove useless statement
cout << "When x is " << x << "y is " << y << endl;
}
return 0; // add a statement to return some value
} // add this as end of definition of function