用c语言实现定义一个包含学生信息（学号，成绩）的链表，使其具有如下功能： (1) 逐个输入学生信息； (2) 逐个显示学生表中所有学生的相关信息； (3) 对数据表进行插入操作； (4) 对数据表进行删除操作。

代码如下：

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

struct student {
    int num;
    int score;
    struct student *next;
};

struct student *create() {
    struct student *head, *p, *q;
    int num, score;

    head = (struct student *)malloc(sizeof(struct student));
    head->next = NULL;
    q = head;

    printf("Please input student's number and score (input -1 to quit):\n");
    scanf("%d%d", &num, &score);
    while (num != -1 && score != -1) {
        p = (struct student *)malloc(sizeof(struct student));
        p->num = num;
        p->score = score;
        p->next = NULL;
        q->next = p;
        q = p;

        printf("Please input student's number and score (input -1 to quit):\n");
        scanf("%d%d", &num, &score);
    }

    return head;
}

void display(struct student *head) {
    struct student *p;

    p = head->next;
    printf("Number\tScore\n");
    while (p != NULL) {
        printf("%d\t%d\n", p->num, p->score);
        p = p->next;
    }
}

void insert(struct student *head) {
    struct student *p, *q;
    int num, score;

    printf("Please input student's number and score to insert:\n");
    scanf("%d%d", &num, &score);

    p = (struct student *)malloc(sizeof(struct student));
    p->num = num;
    p->score = score;
    p->next = NULL;

    q = head;
    while (q->next != NULL && q->next->num < num) {
        q = q->next;
    }

    p->next = q->next;
    q->next = p;
}

void delete(struct student *head) {
    struct student *p, *q;
    int num;

    printf("Please input student's number to delete:\n");
    scanf("%d", &num);

    p = head;
    while (p->next != NULL && p->next->num != num) {
        p = p->next;
    }

    if (p->next == NULL) {
        printf("Not found.\n");
    } else {
        q = p->next;
        p->next = q->next;
        free(q);
    }
}

int main() {
    struct student *head;
    int choice;

    head = create();

    while (1) {
        printf("Please choose an option:\n");
        printf("1. Display all students.\n");
        printf("2. Insert a student.\n");
        printf("3. Delete a student.\n");
        printf("4. Quit.\n");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                display(head);
                break;
            case 2:
                insert(head);
                break;
            case 3:
                delete(head);
                break;
            case 4:
                exit(0);
            default:
                printf("Invalid choice.\n");
        }
    }

    return 0;
}

这个程序中，我们定义了一个结构体 `student`，包含了学号和成绩两个信息，还有一个指向下一个学生结构体的指针。我们使用 `create()` 函数来创建一个链表，使用 `display()` 函数来显示所有学生的信息，使用 `insert()` 函数在链表中插入一个学生的信息，使用 `delete()` 函数在链表中删除一个学生的信息。最后，我们在 `main()` 函数中使用一个无限循环来让用户选择要执行的操作。当用户选择退出程序时，我们使用 `exit()` 函数来终止程序的运行。