我正在尝试创建学生记录并将修改学生记录作为选项之一。但是为了更新，我面临一些问题。以下是我提出问题的代码。
void modify_student()
{
char n[6];
int found = 0;
//clrscr();
cout << "\n\n\tMODIFY STUDENT RECORD";
cout << "\n\n\tEnter The admission no. of The student";
cin >> n;
fp.open("student.dat", ios::in | ios::out);
while (fp.read((char*)&st, sizeof(student)) && found == 0)
{
if (stricmp(st.retadmno(), n) == 0)
{
st.show_student();
cout << "\nEnter The New Details of student" << endl;
st.modify_student();
int negIntegral = -1;
// int pos = -1 * sizeof(st);
long pos = negIntegral * sizeof(st);
fp.seekp(pos, ios::cur);
fp.write((char*)&st, sizeof(student));
cout << "\n\n\t Record Updated";
found = 1;
}
}
fp.close();
if (found == 0)
cout << "\n\n Record Not Found ";
// //getch();
}
Previosly文件看起来像＃
123 XYZ运行上面的代码后更新以将XYZ修改为PQR。该 文件显示
1123 PQR ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ and the entr in the file after 1st one is also not properly aligned. I am not really understanding what is happening here. Please help完整代码在这里＃
#include<fstream>
#include<stdio.h>
#include<iostream>
#include<process.h>
#include<string.h>
#include<iomanip>
#include<conio.h>
using namespace std;
class book
{
char bno[6];
char bname[50];
char aname[20];
public:
void create_book()
{
cout << "\nNEW BOOK ENTRY...\n";
cout << "\nEnter The book no.";
cin >> bno;
fflush(stdin);
cout << "\n\nEnter The Name of The Book ";
fgets(bname,1234,stdin);
fflush(stdin);
cout << "\n\nEnter The Author's Name ";
fgets(aname, 1234, stdin);
fflush(stdin);
cout << "\n\n\nBook Created..";
}
void show_book()
{
cout << "\nBook no. : " << bno;
cout << "\nBook Name : ";
puts(bname);
cout << "Author Name : ";
puts(aname);
}
void modify_book()
{
cout << "\nBook no. : " << bno;
fflush(stdin);
cout << "\nModify Book Name : ";
fgets(bname, 1234, stdin);
fflush(stdin);
cout << "\nModify Author's Name of Book : ";
fgets(aname, 1234, stdin);
}
char* retbno()
{
return bno;
}
void report()
{
cout << bno << setw(30) << bname << setw(30) << aname << endl;
}
}; //class ends here
class student
{
char admno[6];
char name[20];
char stbno[6];
int token;
public:
void create_student()
{
cout << "\nNEW STUDENT ENTRY...\n";
cout << "\nEnter The admission no. ";
cin >> admno;
fflush(stdin);
cout << "\n\nEnter The Name of The Student ";
fgets(name, 1234, stdin);
token = 0;
stbno[0] = '/0';
cout << "\n\nStudent Record Created..";
}
void show_student()
{
cout << "\nAdmission no. : " << admno;
cout << "\nStudent Name : ";
puts(name);
cout << "\nNo of Book issued : " << token;
if (token == 1)
cout << "\nBook No " << stbno;
}
void modify_student()
{
cout << "\nAdmission no. : " << admno;
cout << "\nModify Student Name : ";
fgets(name, 1234, stdin);
}
char* retadmno()
{
return admno;
}
char* retstbno()
{
return stbno;
}
int rettoken()
{
return token;
}
void addtoken()
{
token = 1;
}
void resettoken()
{
token = 0;
}
void fgetstbno(char t[])
{
strcpy_s(stbno,256, t);
}
void report()
{
cout << "\t" << admno << setw(20) << name << setw(10) << token << endl;
}
}; //class ends here
fstream fp, fp1;
book bk;
student st;
//***************************************************************
// function to write in file
//****************************************************************
void write_book()
{
char ch;
fp.open("book.dat", ios::out | ios::app);
do
{
//clrscr();
bk.create_book();
fp.write((char*)&bk, sizeof(book));
cout << "\n\nDo you want to add more record..(y/n?)";
cin >> ch;
} while (ch == 'y' || ch == 'Y');
fp.close();
}
void write_student()
{
char ch;
fp.open("student.dat", ios::out | ios::app);
do
{
st.create_student();
fp.write((char*)&st, sizeof(student));
cout << "\n\ndo you want to add more record..(y/n?)";
cin >> ch;
} while (ch == 'y' || ch == 'Y');
fp.close();
}
//***************************************************************
// function to read specific record from file
//****************************************************************
void display_spb(char n[])
{
cout << "\nBOOK DETAILS\n";
int flag = 0;
fp.open("book.dat", ios::in);
while (fp.read((char*)&bk, sizeof(book)))
{
if (strcmpid(bk.retbno(), n) == 0)
{
bk.show_book();
flag = 1;
}
}
fp.close();
if (flag == 0)
cout << "\n\nBook does not exist";
// //getch();
}
void display_sps(char n[])
{
cout << "\nSTUDENT DETAILS\n";
int flag = 0;
fp.open("student.dat", ios::in);
while (fp.read((char*)&st, sizeof(student)))
{
if ((strcmpi(st.retadmno(), n) == 0))
{
st.show_student();
flag = 1;
}
}
fp.close();
if (flag == 0)
cout << "\n\nStudent does not exist";
// //getch();
}
//***************************************************************
// function to modify record of file
//****************************************************************
void modify_book()
{
char n[6];
int found = 0;
//clrscr();
cout << "\n\n\tMODIFY BOOK REOCORD.... ";
cout << "\n\n\tEnter The book no. of The book";
cin >> n;
fp.open("book.dat", ios::in | ios::out);
while (fp.read((char*)&bk, sizeof(book)) && found == 0)
{
if (strcmpid(bk.retbno(), n) == 0)
{
bk.show_book();
cout << "\nEnter The New Details of book" << endl;
bk.modify_book();
int negIntegral = -1;
//int pos = -1 * sizeof(bk);
long pos = negIntegral * sizeof(bk);
fp.seekp(pos, ios::cur);
fp.write((char*)&bk, sizeof(book));
cout << "\n\n\t Record Updated";
found = 1;
}
}
fp.close();
if (found == 0)
cout << "\n\n Record Not Found ";
// //getch();
}
void modify_student()
{
char n[6];
int found = 0;
//clrscr();
cout << "\n\n\tMODIFY STUDENT RECORD... ";
cout << "\n\n\tEnter The admission no. of The student";
cin >> n;
fp.open("student.dat", ios::in | ios::out);
while (fp.read((char*)&st, sizeof(student)) && found == 0)
{
if (strcmpid(st.retadmno(), n) == 0)
{
st.show_student();
cout << "\nEnter The New Details of student" << endl;
st.modify_student();
int negIntegral = -1;
// int pos = -1 * sizeof(st);
long pos = negIntegral * sizeof(st);
fp.seekp(pos, ios::cur);
fp.write((char*)&st, sizeof(student));
cout << "\n\n\t Record Updated";
found = 1;
}
}
fp.close();
if (found == 0)
cout << "\n\n Record Not Found ";
// //getch();
}
//***************************************************************
// function to delete record of file
//****************************************************************
void delete_student()
{
char n[6];
int flag = 0;
//clrscr();
cout << "\n\n\n\tDELETE STUDENT...";
cout << "\n\nEnter The admission no. of the Student You Want To Delete : ";
cin >> n;
fp.open("student.dat", ios::in | ios::out);
fstream fp2;
fp2.open("Temp.dat", ios::out);
fp.seekg(0, ios::beg);
while (fp.read((char*)&st, sizeof(student)))
{
if (strcmpid(st.retadmno(), n) != 0)
fp2.write((char*)&st, sizeof(student));
else
flag = 1;
}
fp2.close();
fp.close();
remove("student.dat");
rename("Temp.dat", "student.dat");
if (flag == 1)
cout << "\n\n\tRecord Deleted ..";
else
cout << "\n\nRecord not found";
// //getch();
}
void delete_book()
{
char n[6];
//clrscr();
cout << "\n\n\n\tDELETE BOOK ...";
cout << "\n\nEnter The Book no. of the Book You Want To Delete : ";
cin >> n;
fp.open("book.dat", ios::in | ios::out);
fstream fp2;
fp2.open("Temp.dat", ios::out);
fp.seekg(0, ios::beg);
while (fp.read((char*)&bk, sizeof(book)))
{
if (strcmpid(bk.retbno(), n) != 0)
{
fp2.write((char*)&bk, sizeof(book));
}
}
fp2.close();
fp.close();
remove("book.dat");
rename("Temp.dat", "book.dat");
cout << "\n\n\tRecord Deleted ..";
// //getch();
}
//***************************************************************
// function to display all students list
//****************************************************************
void display_alls()
{
//clrscr();
fp.open("student.dat", ios::in);
if (!fp)
{
cout << "ERROR!!! FILE COULD NOT BE OPEN ";
// //getch();
return;
}
cout << "\n\n\t\tSTUDENT LIST\n\n";
cout << "==================================================================\n";
cout << "\tAdmission No." << setw(10) << "Name" << setw(20) << "Book Issued\n";
cout << "==================================================================\n";
while (fp.read((char*)&st, sizeof(student)))
{
st.report();
}
fp.close();
// //getch();
}
//***************************************************************
// function to display Books list
//****************************************************************
void display_allb()
{
//clrscr();
fp.open("book.dat", ios::in);
if (!fp)
{
cout << "ERROR!!! FILE COULD NOT BE OPEN ";
//getch();
return;
}
cout << "\n\n\t\tBook LIST\n\n";
cout << "=========================================================================\n";
cout << "Book Number" << setw(20) << "Book Name" << setw(25) << "Author\n";
cout << "=========================================================================\n";
while (fp.read((char*)&bk, sizeof(book)))
{
bk.report();
}
fp.close();
//getch();
}
//***************************************************************
// function to issue book
//****************************************************************
void book_issue()
{
char sn[6], bn[6];
int found = 0, flag = 0;
//clrscr();
cout << "\n\nBOOK ISSUE ...";
cout << "\n\n\tEnter The student's admission no.";
cin >> sn;
fp.open("student.dat", ios::in | ios::out);
fp1.open("book.dat", ios::in | ios::out);
while (fp.read((char*)&st, sizeof(student)) && found == 0)
{
if (strcmpid(st.retadmno(), sn) == 0)
{
found = 1;
if (st.rettoken() == 0)
{
cout << "\n\n\tEnter the book no. ";
cin >> bn;
while (fp1.read((char*)&bk, sizeof(book)) && flag == 0)
{
if (strcmpid(bk.retbno(), bn) == 0)
{
bk.show_book();
flag = 1;
st.addtoken();
st.fgetstbno(bk.retbno());
int negIntegral = -1;
long pos = negIntegral * sizeof(st);
fp.seekp(pos, ios::cur);
fp.write((char*)&st, sizeof(student));
cout << "\n\n\t Book issued successfully\n\nPlease Note: Write current date \
in backside of book and submit within 15 days fine Rs. 1 for each day \
after 15 days period";
}
}
if (flag == 0)
cout << "Book no does not exist";
}
else
cout << "You have not returned the last book ";
}
}
if (found == 0)
cout << "Student record not exist...";
//getch();
fp.close();
fp1.close();
}
void book_deposit()
{
char sn[6], bn[6];
int found = 0, flag = 0, day, fine;
//clrscr();
cout << "\n\nBOOK DEPOSIT ...";
cout << "\n\n\tEnter The student’s admission no.";
cin >> sn;
fp.open("student.dat", ios::in | ios::out);
fp1.open("book.dat", ios::in | ios::out);
while (fp.read((char*)&st, sizeof(student)) && found == 0)
{
if (strcmpid(st.retadmno(), sn) == 0)
{
found = 1;
if (st.rettoken() == 1)
{
while (fp1.read((char*)&bk, sizeof(book)) && flag == 0)
{
if (strcmpid(bk.retbno(), st.retstbno()) == 0)
{
bk.show_book();
flag = 1;
cout << "\n\nBook deposited in no. of days";
cin >> day;
if (day>15)
{
fine = (day - 15) * 1;
cout << "\n\nFine has to deposited Rs. " << fine;
}
st.resettoken();
int negIntegral = -1;
int pos = negIntegral * sizeof(st);
fp.seekp(pos, ios::cur);
fp.write((char*)&st, sizeof(student));
cout << "\n\n\t Book deposited successfully";
}
}
if (flag == 0)
cout << "Book no does not exist";
}
else
cout << "No book is issued..please check!!";
}
}
if (found == 0)
cout << "Student record not exist...";
fp.close();
fp1.close();
}
//***************************************************************
// INTRODUCTION FUNCTION
//****************************************************************
void intro()
{
//clrscr();
//gotoxy(35,11);
cout << "LIBRARY";
//gotoxy(35,14);
cout << "MANAGEMENT";
//gotoxy(35,17);
cout << "SYSTEM";
}
//***************************************************************
// ADMINISTRATOR MENU FUNCTION
//****************************************************************
void admin_menu()
{
//clrscr();
int ch2;
cout << "\n\n\n\tADMINISTRATOR MENU";
cout << "\n\n\t1.CREATE STUDENT RECORD";
cout << "\n\n\t2.DISPLAY ALL STUDENTS RECORD";
cout << "\n\n\t3.DISPLAY SPECIFIC STUDENT RECORD ";
cout << "\n\n\t4.MODIFY STUDENT RECORD";
cout << "\n\n\t5.DELETE STUDENT RECORD";
cout << "\n\n\t6.CREATE BOOK ";
cout << "\n\n\t7.DISPLAY ALL BOOKS ";
cout << "\n\n\t8.DISPLAY SPECIFIC BOOK ";
cout << "\n\n\t9.MODIFY BOOK ";
cout << "\n\n\t10.DELETE BOOK ";
cout << "\n\n\t11.BACK TO MAIN MENU";
cout << "\n\n\tPlease Enter Your Choice (1-11) ";
cin >> ch2;
switch (ch2)
{
case 1: //clrscr();
write_student(); break;
case 2: display_alls(); break;
case 3:
char num[6];
//clrscr();
cout << "\n\n\tPlease Enter The Admission No. ";
cin >> num;
display_sps(num);
break;
case 4: modify_student(); break;
case 5: delete_student(); break;
case 6: //clrscr();
write_book(); break;
case 7: display_allb(); break;
case 8: {
char num[6];
//clrscr();
cout << "\n\n\tPlease Enter The book No. ";
cin >> num;
display_spb(num);
break;
}
case 9: modify_book(); break;
case 10: delete_book(); break;
case 11: return;
default:cout << "\a";
}
admin_menu();
}
//***************************************************************
// THE MAIN FUNCTION OF PROGRAM
//****************************************************************
void main()
{
char ch;
intro();
do
{
//clrscr();
cout << "\n\n\n\tMAIN MENU";
cout << "\n\n\t01. BOOK ISSUE";
cout << "\n\n\t02. BOOK DEPOSIT";
cout << "\n\n\t03. ADMINISTRATOR MENU";
cout << "\n\n\t04. EXIT";
cout << "\n\n\tPlease Select Your Option (1-4) ";
//ch = getche();
ch = std::cin.get();
switch (ch)
{
case '1'://clrscr();
book_issue();
break;
case '2':book_deposit();
break;
case '3':admin_menu();
break;
case '4':exit(0);
default:cout << "\a";
}
} while (ch != '4');
system("pause");
}
答案 0 :(得分：0)
由于并未显示所有代码，因此无法100％确定，但我怀疑st是包含非平凡对象的类实例。
例如，如果学生类包含std::string对象，则不能fread或fwrite直接指向磁盘文件。