要求用C语言编写:1.先编写一个带结构的文件，存入电脑，要求第一行从左到右的内容依次是：序号、姓名、班级、学号，每排每列对齐，没有对齐的地方用空格补齐。2.从电脑中能够读入这个带结构的文件，并进行删增改后，重新存入电脑，3.这个文件要有纵横结构，每横表示一个记录4. 编出来的代码要能够在c的运行界面进行后续的插入、删除和修改

以下是一个简单的实现，用于演示如何实现上述要求。请注意，这只是一个示例，实际应用中可能需要进行更多的错误检查和边界情况处理。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_NAME_LEN 20
#define MAX_CLASS_LEN 10
#define MAX_ID_LEN 20

typedef struct {
    int id;
    char name[MAX_NAME_LEN];
    char class[MAX_CLASS_LEN];
    char student_id[MAX_ID_LEN];
} Record;

void print_record(const Record* record) {
    printf("%-10d%-20s%-10s%-20s\n", record->id, record->name, record->class, record->student_id);
}

void print_header() {
    printf("%-10s%-20s%-10s%-20s\n", "序号", "姓名", "班级", "学号");
}

void read_records(const char* filename, Record** records_ptr, int* num_records_ptr) {
    FILE* fp;
    int num_records = 0;
    Record* records = NULL;
    char line[100];
    char* token;

    fp = fopen(filename, "r");
    if (fp == NULL) {
        printf("Failed to open file %s for reading.\n", filename);
        return;
    }

    fgets(line, sizeof(line), fp); // skip header
    while (fgets(line, sizeof(line), fp)) {
        records = realloc(records, (num_records + 1) * sizeof(Record));
        token = strtok(line, " ");
        records[num_records].id = atoi(token);
        token = strtok(NULL, " ");
        strncpy(records[num_records].name, token, MAX_NAME_LEN);
        records[num_records].name[MAX_NAME_LEN - 1] = '\0';
        token = strtok(NULL, " ");
        strncpy(records[num_records].class, token, MAX_CLASS_LEN);
        records[num_records].class[MAX_CLASS_LEN - 1] = '\0';
        token = strtok(NULL, " ");
        strncpy(records[num_records].student_id, token, MAX_ID_LEN);
        records[num_records].student_id[MAX_ID_LEN - 1] = '\0';
        num_records++;
    }

    fclose(fp);

    *records_ptr = records;
    *num_records_ptr = num_records;
}

void write_records(const char* filename, const Record* records, int num_records) {
    FILE* fp;
    int i;

    fp = fopen(filename, "w");
    if (fp == NULL) {
        printf("Failed to open file %s for writing.\n", filename);
        return;
    }

    print_header();
    for (i = 0; i < num_records; i++) {
        print_record(&records[i]);
        fprintf(fp, "%d %s %s %s\n", records[i].id, records[i].name, records[i].class, records[i].student_id);
    }

    fclose(fp);
}

void add_record(Record** records_ptr, int* num_records_ptr) {
    Record* records = *records_ptr;
    int num_records = *num_records_ptr;
    Record record;
    char buffer[100];

    printf("请输入新记录的信息：\n");

    printf("序号：");
    fgets(buffer, sizeof(buffer), stdin);
    record.id = atoi(buffer);

    printf("姓名：");
    fgets(record.name, MAX_NAME_LEN, stdin);
    record.name[strlen(record.name) - 1] = '\0';

    printf("班级：");
    fgets(record.class, MAX_CLASS_LEN, stdin);
    record.class[strlen(record.class) - 1] = '\0';

    printf("学号：");
    fgets(record.student_id, MAX_ID_LEN, stdin);
    record.student_id[strlen(record.student_id) - 1] = '\0';

    records = realloc(records, (num_records + 1) * sizeof(Record));
    records[num_records] = record;

    *records_ptr = records;
    *num_records_ptr = num_records + 1;
}

void delete_record(Record** records_ptr, int* num_records_ptr) {
    Record* records = *records_ptr;
    int num_records = *num_records_ptr;
    int id;
    int i, j;

    printf("请输入要删除的记录的序号：");
    scanf("%d", &id);

    for (i = 0; i < num_records; i++) {
        if (records[i].id == id) {
            for (j = i; j < num_records - 1; j++) {
                records[j] = records[j + 1];
            }
            *records_ptr = realloc(records, (num_records - 1) * sizeof(Record));
            *num_records_ptr = num_records - 1;
            printf("已删除记录：\n");
            print_header();
            print_record(&records[i]);
            return;
        }
    }

    printf("未找到序号为 %d 的记录。\n", id);
}

void modify_record(Record* records, int num_records) {
    int id;
    int i;

    printf("请输入要修改的记录的序号：");
    scanf("%d", &id);

    for (i = 0; i < num_records; i++) {
        if (records[i].id == id) {
            printf("请输入修改后的信息：\n");

            printf("姓名：");
            fgets(records[i].name, MAX_NAME_LEN, stdin);
            records[i].name[strlen(records[i].name) - 1] = '\0';

            printf("班级：");
            fgets(records[i].class, MAX_CLASS_LEN, stdin);
            records[i].class[strlen(records[i].class) - 1] = '\0';

            printf("学号：");
            fgets(records[i].student_id, MAX_ID_LEN, stdin);
            records[i].student_id[strlen(records[i].student_id) - 1] = '\0';

            printf("已修改记录为：\n");
            print_header();
            print_record(&records[i]);
            return;
        }
    }

    printf("未找到序号为 %d 的记录。\n", id);
}

int main() {
    char filename[] = "records.txt";
    Record* records = NULL;
    int num_records = 0;
    int option;
    char buffer[100];

    read_records(filename, &records, &num_records);

    do {
        printf("\n请选择要进行的操作：\n");
        printf("1. 显示所有记录\n");
        printf("2. 添加记录\n");
        printf("3. 删除记录\n");
        printf("4. 修改记录\n");
        printf("5. 保存并退出\n");
        printf("请选择：");
        fgets(buffer, sizeof(buffer), stdin);
        option = atoi(buffer);

        switch (option) {
            case 1:
                print_header();
                for (int i = 0; i < num_records; i++) {
                    print_record(&records[i]);
                }
                break;
            case 2:
                add_record(&records, &num_records);
                break;
            case 3:
                delete_record(&records, &num_records);
                break;
            case 4:
                modify_record(records, num_records);
                break;
            case 5:
                write_records(filename, records, num_records);
                break;
            default:
                printf("无效的选项，请重新选择。\n");
        }
    } while (option != 5);

    free(records);

    return 0;
}