black screen

i am a beginner. when i compile the source code, it shows no error. but, when run, only black screen appeared. hope anyone could help me.

  #include<iostream> 
#include<fstream> 
#include<iomanip>
#include<stdlib.h>
#include<conio.h>
#include<windows.h>

using namespace std;

class student 
{ 
	int rollno; 
	char name[50]; 
	int pmarks, cmarks, mmarks, emarks, cs_marks; 
	double per; 
	char grade; 
	void calculate(); //function to calculate grade 

	public: void getdata(); //function to accept data from user 
	void showdata() const; //function to show data on screen 
	void showtabular() const; 
	int retrollno() const; 
}; //class ends here

void student::calculate() 
{ 
	per=(pmarks+cmarks+mmarks+emarks+cs_marks)/5.0; 
	if (per>=60) 
		grade='A';
		
	else if(per>=50) 
		grade='B'; 
		
	else if(per>=33) 
		grade='C'; 
		
	else grade='F'; 
}

void student::getdata() 
{ 
	cout<<"\nEnter The roll number of student "; 
	cin>>rollno; 
	cout<<"\n\nEnter The Name of student "; 
	cin.ignore(); 
	cin.getline(name,50); 
	cout<<"\nEnter The marks in physics out of 100 : "; 
	cin>>pmarks; 
	cout<<"\nEnter The marks in chemistry out of 100 : "; 
	cin>>cmarks; 
	cout<<"\nEnter The marks in maths out of 100 : "; 
	cin>>mmarks; 
	cout<<"\nEnter The marks in english out of 100 : "; 
	cin>>emarks; 
	cout<<"\nEnter The marks in computer science out of 100 : "; 
	cin>>cs_marks; 
	calculate(); 
}

void student::showdata() const 
{ 
	cout<<"\nRoll number of student : "<<rollno; 
	cout<<"\nName of student : "<<name; 
	cout<<"\nMarks in Physics : "<<pmarks; 
	cout<<"\nMarks in Chemistry : "<<cmarks; 
	cout<<"\nMarks in Maths : "<<mmarks; 
	cout<<"\nMarks in English : "<<emarks; 
	cout<<"\nMarks in Computer Science :"<<cs_marks; 
	cout<<"\nPercentage of student is :"<<per; 
	cout<<"\nGrade of student is :"<<grade; 
}

void student::showtabular() const 
{ 
	cout<<rollno<<setw(6)<<" "<<name<<setw(10)<<pmarks<<setw(4)<<cmarks<<setw(4)<<mmarks<<setw(4) <<emarks<<setw(4)<<cs_marks<<setw(8)<<per<<setw(6)<<grade<<endl; 
}

int student::retrollno() const 
{ 
	return rollno; 
}

void writestudent(); 
void displayall();  
void displaysp(int); 
void modifystudent(int); 
void deletestudent(int); 
void classresult();  
void result(); 
void intro();  
void entrymenu();

int main() 
{ 
	char ch; 
	cout.setf(ios::fixed|ios::showpoint); 
	cout<<ch; 
	
	switch(ch) 
	{ 
		case '1': result(); 
		break; 
		
		case '2': entrymenu(); 
		break; 
		
		case '3': break; 
		default :cout<<"\a"; 
	} 

	while(ch!='3'); 
	return 0; 
}

void writestudent() 
{ 
	student st; 
	ofstream outFile; 
	outFile.open("student.dat",ios::binary|ios::app); 
	st.getdata(); 
	outFile.write(reinterpret_cast <char *> (&st), sizeof(student)); 
	outFile.close(); 
	cout<<"\n\nStudent record Has Been Created "; 
	cin.ignore(); 
	cin.get(); 
}

void displayall() 
{ 
	student st; 
	ifstream inFile; 
	inFile.open("student.dat",ios::binary); 
	
	if(!inFile) 
	{ 
		cout<<"File could not be open !! Press any Key..."; 
		cin.ignore(); 
		cin.get(); 
		return; 
	} 
	
	cout<<"\n\n\n\t\tDISPLAY ALL RECORD !!!\n\n"; 
	
	while(inFile.read(reinterpret_cast <char *> (&st), sizeof(student))) 
	{ 
		st.showdata(); 
		cout<<"\n\n====================================\n"; 
	} 
	
	inFile.close(); 
	cin.ignore(); 
	cin.get(); 
}

void displaysp(int n) 
{ 
	student st; 
	ifstream inFile; 
	inFile.open("student.dat",ios::binary); 
	
	if(!inFile) 
	{ 
		cout<<"File could not be open !! Press any Key..."; 
		cin.ignore(); 
		cin.get(); 
		return; 
	} 
	
	bool flag=false; 
	
	while(inFile.read(reinterpret_cast<char *> (&st), sizeof(student))) 
	{ 
		if(st.retrollno()==n) 
		{ 
			st.showdata(); 
			flag=true; 
		} 
	} 
	
	inFile.close(); 
	
	if(flag==false) 
		cout<<"\n\nrecord not exist"; 
		cin.ignore(); 
		cin.get(); 
}

void modifystudent(int n) 
{ 
	bool found=false; 
	student st; 
	fstream File; 
	File.open("student.dat",ios::binary|ios::in|ios::out); 
	
	if(!File) 
	{ 
		cout<<"File could not be open !! Press any Key..."; 
		cin.ignore(); 
		cin.get(); 
		return; 
	} 
	
	while(!File.eof() && found==false) 
	{
		File.read(reinterpret_cast<char *> (&st), sizeof(student)); 
		
		if(st.retrollno()==n) 
		{ 
			st.showdata(); 
			cout<<"\n\nPlease Enter The New Details of student"<<endl; 
			st.getdata(); 
			int pos=(-1)*static_cast<int>(sizeof(st)); 
			File.seekp(pos,ios::cur); 
			File.write(reinterpret_cast<char *> (&st), sizeof(student)); 
			cout<<"\n\n\t Record Updated"; 
			found=true; 
		} 
	} 
	
	File.close(); 
	if(found==false) 
		cout<<"\n\n Record Not Found "; 
		cin.ignore(); 
		cin.get();
}

void deletestudent(int n) 
{ 
	student st; 
	ifstream inFile; 
	inFile.open("student.dat",ios::binary); 
	
	if(!inFile) 
	{ 
		cout<<"File could not be open !! Press any Key..."; 
		cin.ignore(); 
		cin.get(); 
		return; 
	} 
	ofstream outFile; 
	outFile.open("Temp.dat",ios::out); 
	inFile.seekg(0,ios::beg); 
	
	while(inFile.read(reinterpret_cast <char *> (&st), sizeof(student))) 
	{ 
		if(st.retrollno()!=n) 
		{ 
			outFile.write(reinterpret_cast <char *> (&st), sizeof(student)); 
		} 
	} 
	outFile.close(); 
	inFile.close(); 
	remove("student.dat"); 
	rename("Temp.dat","student.dat"); 
	cout<<"\n\n\tRecord Deleted .."; 
	cin.ignore(); 
	cin.get(); 
}

void classresult() 
{ 
	student st; 
	ifstream inFile; 
	inFile.open("student.dat",ios::binary); 
	
	if(!inFile) 
	{ 
		cout<<"File could not be open !! Press any Key..."; 
		cin.ignore(); 
		cin.get(); 
		return; 
	} 
	cout<<"\n\n\t\tALL STUDENTS RESULT \n\n"; 
	cout<<"==========================================================\n"; 
	cout<<"R.No Name P C M E CS %age Grade"<<endl; 
	cout<<"==========================================================\n"; 
	
	while(inFile.read(reinterpret_cast <char *> (&st), sizeof(student))) 
	{ 
		st.showtabular(); 
	} 
	cin.ignore(); 
	cin.get(); 
	inFile.close(); 
}

void result() 
{ 
	char ch; 
	int rno; 
	system("cls"); 
	cout<<"\n\n\n\tRESULT MENU"; 
	cout<<"\n\n\n\t1. Class Result"; 
	cout<<"\n\n\t2. Student Report Card"; 
	cout<<"\n\n\t3. Back to Main Menu"; 
	cout<<"\n\n\n\tEnter Choice (1/2/3)? "; 
	cin>>ch; 
	system("cls"); 
	
	switch(ch) 
	{ 
		case '1' : classresult(); 
			break; 
		
		case '2' : cout<<"\n\n\tEnter Roll Number Of Student : "; 
			cin>>rno; 
			displaysp(rno); 
			break; 
			
		case '3' : break; 
			default: cout<<"\a"; 
	} 
}

void intro() 
{ 
	cout<<"\n\n\n\t\t STUDENT"; 
	cout<<"\n\n\t\tREPORT CARD"; 
	cout<<"\n\n\t\t PROJECT"; 
	cout<<"\n\n\n\tMADE BY : SULABH AGRAWAL"; 
	cout<<"\n\tSCHOOL : CAMBRIDGE SCHOOL"; 
	cin.get(); 
}

void entrymenu() 
{ 
	char ch; 
	int num; 
	system("cls"); 
	cout<<"\n\n\n\tENTRY MENU"; 
	cout<<"\n\n\t1.CREATE STUDENT RECORD"; 
	cout<<"\n\n\t2.DISPLAY ALL STUDENTS RECORDS"; 
	cout<<"\n\n\t3.SEARCH STUDENT RECORD "; 
	cout<<"\n\n\t4.MODIFY STUDENT RECORD"; 
	cout<<"\n\n\t5.DELETE STUDENT RECORD"; 
	cout<<"\n\n\t6.BACK TO MAIN MENU"; 
	cout<<"\n\n\tPlease Enter Your Choice (1-6) "; 
	cin>>ch; system("cls"); 
	
	switch(ch) 
	{ 
		case '1': writestudent(); 
			break; 
			
		case '2': displayall(); 
			break; 
		
		case '3': cout<<"\n\n\tPlease Enter The roll number "; 
			cin>>num; displaysp(num); 
			break; 
			
		case '4': cout<<"\n\n\tPlease Enter The roll number "; 
			cin>>num; modifystudent(num);
			break; 
			
		case '5': cout<<"\n\n\tPlease Enter The roll number "; 
			cin>>num; 
			deletestudent(num);
			break; 
			
		case '6': break; 
			default: cout<<"\a"; 
			entrymenu(); 
	} 
}

coder777 (8439)

Line 97: I guess you want a cin there. And there should be a cout for the user what to do (i.e. "enter 1/2/3").

Line 111: It runs either not at all or infinitely.

lastchance (6980)

Did you write all that, @RTsuNa08?

Start at int main() and step through it line by line, explaining to yourself what you wrote on each line and what each one does ... and with what values. You will soon find your mistake.

Enoizat (1342)

lastchance wrote:
Did you write all that, @RTsuNa08?

Good instinct.
http://www.cppforschool.com/project/student-report-card-project.html

lastchance (6980)

Thanks @Enoizat. I notice that there are a few slightly different variants at various websites.

@RTsuNa08, if you go to the ANSI C++ tab on the link that @Enoizat gave, you will find that you have missed some rather crucial lines out of main().

RTsuNa08 (4)

it is not me who right this, it is my lecturer who give this as an assignment, but it is still incomplete, i have repaired this source code until it has not any error but it show a black screen, before i repaired it, there are a lot of error,

keskiverto (10363)

Even in that case there were two possible cases:
1. The program was incomplete and your task is to add missing pieces.
2. The program was incorrect and your task is to change code.

Either way, you need to understand what is in the code and what should be in the code.

As said above, the function main() has obvious logical errors. Your assignment is to figure them out.

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