Lỗi: ld returned 1 exit status khi code trên Dev C++

[poseidon (duong vui)]

Mình viết một file Sinhvien.h có nội dung như sau:

#include<iostream>
#include<string>
using namespace std;
class Student
{
	private:
		string id,course,bir,hometown;
		float pM,pB,pC,pW;
	public:
		void setPoint(float pointMath,float pointBiology,float pointC,float pointWeb);
		void setInformation(string ID, string classname, string birthday, string hometown);
		float getPM()
		{
			return this->pM;
		}
		float getpB()
		{
			return this->pB;
		}
		float getpC()
		{
			return this->pC;
		}
		float getpW()
		{
			return this->pW;
		}
	void Input();
	float Average(float pM,float pB, float pC, float pW);
	void Classification();
	void Output();
	float Check(float point);
	Student(void);
	~Student(void);
};

và 1 file Sinhvien.cpp có nội dung:

#include "Sinhvien.h"
using namespace std;
void Student::setPoint(float pointMath,float pointBiology,float pointC,float pointWeb)
{
	this->pM=pointMath;
	this->pB=pointBiology;
	this->pC=pointC;
	this->pW=pointWeb;
}
void Student::setInformation(string ID, string classname, string birthday, string hometown)
{
	this->id=ID;
	this->course=classname;
	this->bir=birthday;
	this->hometown=hometown;
}
float Student::Check(float point)
{
	char ch, s1='Y',s2='y';
	while(point <0||point>10)
	{
		cout<<endl<<"Nhap sai.";
		cout<<endl<<"Ban co muon nhap lai";
		cin>>ch;
		if(ch==s1||ch==s2)
		{
		    cout<<endl<<"Nhap diem: ";
		    cin>>point;
		}
		else
		{
			point=0;
			break;
		}
	}
	return point;
}
void Student::Input()
{
	string s1,s2,s3,s4;
	float f1,f2,f3,f4;
	cout<<"Nhap ma sinh vien: ";
	cin>>s1;
	cout<<endl<<"Nhap lop: ";
	cin>>s2;
	cout<<endl<<"Nhap ngay sinh: ";
	cin>>s3;
	cout<<endl<<"Nhap que quan: ";
    cin>>s4;
    setInformation(s1,s2,s3,s4);
	cout<<endl<<"Nhap diem mon toan: ";
	cin>>f1;
	Check(f1);
	cout<<endl<<"Nhap diem mon sinh: ";
	cin>>f2;
	Check(f2);
	cout<<endl<<"Nhap diem mon C: ";
	cin>>f3;
	Check(f3);
	cout<<endl<<"Nhap diem mon web: ";
	cin>>f4;
	Check(f4);
	setPoint(f1,f2,f3,f4);
}
float Student:: Average(float pM,float pB, float pC, float pW)
{
	return (pM+pB+pC+pW)/4;
}
void Student::Classification()
{
	float arg=Average(pM,pB,pC,pW);
	if(arg<5)
			    cout<<endl<<"Xep loai yeu";
			else
			    if(arg<6)
			        cout<<endl<<"Xep loai trung binh";
			    else
			        if(arg<7)
			            cout<<endl<<"Xep loai trung binh kha";
			        else
			            if(arg<8)
			                cout<<endl<<"Xep loai kha";
			            else
			                if(arg<9)
			                cout<<endl<<"Xep loai gioi";
			                else
			                    cout<<endl<<"Xep loai xuat sac";
	}
void Student::Output()
{
	cout<<endl<<"Diem trung binh: "<<Average(pM,pB,pC,pW);
	Classification();
	}
void Student::Student()
{
}
void Student::~Student(void)
{
}

file main.cpp:

#include<iostream>
#include "Sinhvien.h"
using namespace std;
int main()
{
	Student s;
	s.Input();
	s.Output();
}

nhưng không hiểu sao khi chạy thì nó lại thông báo lỗi:

main.cpp:(.text+0x1b): undefined reference to `Student::Student()'
main.cpp:(.text+0x27): undefined reference to `Student::Input()'
main.cpp:(.text+0x33): undefined reference to `Student::Output()'
main.cpp:(.text+0x3f): undefined reference to `Student::~Student()'
main.cpp:(.text+0x55): undefined reference to `Student::~Student()'
[Error] ld returned 1 exit status

[Sherly1001]

Do Dev nó không linker được những file.o đã build đó bạn.
Mình không dùng Dev nên không biết thế nào. Nhưng nếu dùng cmd bạn có thể chạy lần lượt những lệnh sau:

g++ -c Sinhvien.cpp                 // make file Sinhvien.o
g++ -c main.cpp                     // make file main.o
g++ main.o Sinhvien.o -o main.exe   // link file main.o and file Sinhvien.o and export to file main.exe

[poseidon (duong vui)]

cảm ơn bạn, mình fix đc rồi. tại mình chưa include file Sinhvien.cpp vào file main.