Delete a file cannot be deleted

Hello every one, I'm happy to here and ask you a question, in other words, let's solve a pazzle.
I downloaded some TV-Shows from the Internet, and I want to convert them to AVI files because that could save a lot of space of hard-disk. But during using the third-party software WinMPG Video Convert, an error occured and showed a message to me telling that the file I selected had no video or audio stream, but it is impossible, because the file can be played normally. Then, I found this software built a zero-size file on my hard-disk, and while I tried to delete this file, Windows had no response soon. Why? I cannot explain that, but it's interesting and unbelievable that when I tried to write some C# codes to delete this file automatily, an exception occured when I debugged it, the message showed me that the file I tried to delete was locked by another process. What? Which one? I don't know. I closed my application and tried to delete again. I'm really hope that it can success, but it does not, the difference is that Windows responsed and showed me the same message. Then, I opened the taskmgr and found a process named conime.exe(calm down man, it does not a virus, on the contrary, it is a normal process that called by my application, because my application is an Console Application, it of course will call the Console IME), I killed it and tried to delete the file once again. SUCCESS! What did my application do? Could you explain the pazzle for me? Thanks lot.
Best Regards,
Wei CHEN
there is a file,use c write a System Requirements: A. To make the program as user-friendly as possible, use the following menu to start. 1. Import grades for a course 2. Delete a course 3. Calculate GPA 4. Export file with GPA 5. Quit User will choose the functions using the index number: 1: ask user to import a file from which the grades will be added to students.txt. a) The program should ask the user to input the course name before input the file name. It is assumed that the length of course name is less than 20. b) If the course name inputted by user exists in students.txt, gives user a warning. User can choose to replace the old grades with new or not. If user choose not to replace, go back to main menu. c) If the course name does not exist in students.txt, ask the user to give the file name to import. d) If it is found that a student ID in this imported file cannot be found in the students.txt, do not import and give the warning. Each ID contains 10 digits. It is assumed that each file has been sorted according to ID in ascending order before it is imported. 2: ask user to input the course name to delete. If the course name does not exist in students.txt, gives a warning. 3: the system will calculate GPA for each student in students.txt and put the GPA in the file too. Keep two decimal points in GPA. 4: when user has this choice, the system will display a sub-menu. 1. Sorted in ID (ascending) 2. Sorted in GPA (descending) 3. Back to main menu In this sub-menu, if user chooses 1 or 2, the system will ask user to input a file name to export to. If user chooses 3, system goes back to main menu. 5: Quit the system.
07-16
下面是根据您提供的需求编写的C程序代码,实现了系统的功能要求: ```c #include <stdio.h> #include <stdlib.h> #include <string.h> #define MAX_COURSE_NAME_LENGTH 20 #define MAX_STUDENT_ID_LENGTH 11 typedef struct { char student_id[MAX_STUDENT_ID_LENGTH]; char course_name[MAX_COURSE_NAME_LENGTH]; float grade; } Student; void import_grades(Student *students, int *num_students); void delete_course(Student *students, int *num_students); void calculate_gpa(Student *students, int num_students); void export_file(Student *students, int num_students); void sort_by_id(Student *students, int num_students); void sort_by_gpa(Student *students, int num_students); int main() { Student students[100]; // 假设最多有100个学生 int num_students = 0; int choice; do { printf("\n=== Main Menu ===\n"); printf("1. Import grades for a course\n"); printf("2. Delete a course\n"); printf("3. Calculate GPA\n"); printf("4. Export file with GPA\n"); printf("5. Quit\n"); printf("Enter your choice: "); scanf("%d", &choice); switch (choice) { case 1: import_grades(students, &num_students); break; case 2: delete_course(students, &num_students); break; case 3: calculate_gpa(students, num_students); break; case 4: export_file(students, num_students); break; case 5: printf("Quitting the system...\n"); break; default: printf("Invalid choice! Please try again.\n"); } } while (choice != 5); return 0; } void import_grades(Student *students, int *num_students) { char course[MAX_COURSE_NAME_LENGTH]; char file_name[100]; printf("Enter the course name: "); scanf("%s", course); // Check if the course already exists for (int i = 0; i < *num_students; i++) { if (strcmp(students[i].course_name, course) == 0) { printf("Warning: Course already exists.\n"); printf("Do you want to replace the old grades? (y/n): "); char replace_choice; scanf(" %c", &replace_choice); if (replace_choice == 'n' || replace_choice == 'N') { return; } } } printf("Enter the file name to import: "); scanf("%s", file_name); FILE *file = fopen(file_name, "r"); if (file == NULL) { printf("Error opening file.\n"); return; } char student_id[MAX_STUDENT_ID_LENGTH]; float grade; while (fscanf(file, "%s %f", student_id, &grade) == 2) { if (strlen(student_id) != MAX_STUDENT_ID_LENGTH - 1) { printf("Warning: Invalid student ID.\n"); continue; } // Check if student ID already exists int existing_student_index = -1; for (int i = 0; i < *num_students; i++) { if (strcmp(students[i].student_id, student_id) == 0) { existing_student_index = i; break; } } if (existing_student_index != -1) { // Update existing student's grade students[existing_student_index].grade = grade; strcpy(students[existing_student_index].course_name, course); } else { // Add new student strcpy(students[*num_students].student_id, student_id); strcpy(students[*num_students].course_name, course); students[*num_students].grade = grade; (*num_students)++; } } fclose(file); } void delete_course(Student *students, int *num_students) { char course[MAX_COURSE_NAME_LENGTH]; printf("Enter the course name to delete: "); scanf("%s", course); int deleted = 0; for (int i = 0; i < *num_students; i++) { if (strcmp(students[i].course_name, course) == 0) { // Shift remaining elements to fill the gap for (int j = i; j < (*num_students - 1); j++) { strcpy(students[j].student_id, students[j+1].student_id); strcpy(students[j].course_name, students[j+1].course_name); students[j].grade = students[j+1].grade; } (*num_students)--; deleted = 1; } } if (!deleted) { printf("Warning: Course does not exist.\n"); } } void calculate_gpa(Student *students, int num_students) { for (int i = 0; i < num_students; i++) { printf("Student ID: %s\n", students[i].student_id); printf("Course Name: %s\n", students[i].course_name); printf("Grade: %.2f\n", students[i].grade); // Calculate GPA float gpa = students[i].grade / 20.0; // Assuming grade is out of 100 printf("GPA: %.2f\n", gpa); // Update GPA in the structure students[i].grade = gpa; } } void export_file(Student *students, int num_students) { int sub_choice; do { printf("\n=== Export Menu ===\n"); printf("1. Sorted in ID (ascending)\n"); printf("2. Sorted in GPA (descending)\n"); printf("3. Back to main menu\n"); printf("Enter your choice: "); scanf("%d", &sub_choice); switch (sub_choice) { case 1: sort_by_id(students, num_students); break; case 2: sort_by_gpa(students, num_students); break; case 3: printf("Returning to main menu...\n"); break; default: printf("Invalid choice! Please try again.\n"); } } while (sub_choice != 3); } void sort_by_id(Student *students, int num_students) { // Use bubble sort algorithm to sort by student ID in ascending order for (int i = 0; i < num_students - 1; i++) { for (int j = 0; j < num_students - i - 1; j++) { if (strcmp(students[j].student_id, students[j+1].student_id) > 0) { // Swap students Student temp = students[j]; students[j] = students[j+1]; students[j+1] = temp; } } } char file_name[100]; printf("Enter the file name to export: "); scanf("%s", file_name); FILE *file = fopen(file_name, "w"); if (file == NULL) { printf("Error opening file.\n"); return; } for (int i = 0; i < num_students; i++) { fprintf(file, "%s %s %.2f\n", students[i].student_id, students[i].course_name, students[i].grade); } fclose(file); printf("Export successful.\n"); } void sort_by_gpa(Student *students, int num_students) { // Use bubble sort algorithm to sort by GPA in descending order for (int i = 0; i < num_students - 1; i++) { for (int j = 0; j < num_students - i - 1; j++) { if (students[j].grade < students[j+1].grade) { // Swap students Student temp = students[j]; students[j] = students[j+1]; students[j+1] = temp; } } } char file_name[100]; printf("Enter the file name to export: "); scanf("%s", file_name); FILE *file = fopen(file_name, "w"); if (file == NULL) { printf("Error opening file.\n"); return; } for (int i = 0; i < num_students; i++) { fprintf(file, "%s %s %.2f\n", students[i].student_id, students[i].course_name, students[i].grade); } fclose(file); printf("Export successful.\n"); } ``` 这是一个简单的示例,实现了您所描述的系统要求。您可以根据需要进行修改和扩展。请注意,此代码仅满足基本功能,可能需要根据实际需求进行进一步的错误处理和输入验证。
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