sub Printf_Null() { my($CurrNum,$MaxNum) = @_; if(($CurrNum<$MaxNum))#18-7=11 { for(my $i=0;$i<($MaxNum-$CurrNum);$i++ ) { print FH " "; } } }
时间: 2023-08-13 14:03:25 浏览: 51
这段代码是一个 Perl 子程序,名为 `Printf_Null`,它接受两个参数 `$CurrNum` 和 `$MaxNum`。这个程序的主要作用是在打印一个文本文件时,在每一行的开头打印一些空格,使得该行文本能够按照某种格式对齐。
具体来说,第一行的开头不会打印任何空格。对于第二行及以后的每一行,程序会根据当前行数 `$CurrNum` 和最大行数 `$MaxNum`,计算出需要打印的空格数量,并在每行的开头打印这些空格。程序使用了一个 for 循环来打印空格,循环次数为最大行数减去当前行数。
需要注意的是,该程序中的 `FH` 是一个文件句柄,它指向一个已经打开的文件。在程序中,使用 `print` 语句将空格写入到该文件中。
相关问题
解释sub PAT_Printf_Null() { my($CurrNum,$MaxNum) = @_; if(($CurrNum<$MaxNum))#18-7=11 { for(my $i=0;$i<($MaxNum-$CurrNum);$i++ ) { print FH " "; } } }
这是一个Perl语言的子程序(subroutine),接受两个参数$CurrNum和$MaxNum。它的作用是在输出文本时,在数字$CurrNum和$MaxNum之间插入空格,使得它们对齐。具体来说,如果$CurrNum小于$MaxNum,就在输出前先输出若干个空格,使得两个数字的位数相同。其中,for循环输出了$MaxNum-$CurrNum个空格,使用文件句柄FH来输出空格。
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.
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。
相关推荐
![rar](https://img-home.csdnimg.cn/images/20210720083606.png)
![rar](https://img-home.csdnimg.cn/images/20210720083606.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![zip](https://img-home.csdnimg.cn/images/20210720083736.png)