创建一个c语言程序学生成绩管理系统包括添加学生成绩，查询学生成绩，更新学生成绩，统计学生成绩，输出学生成绩，退出系统

好的，以下是一个简单的 C 语言学生成绩管理系统的代码示例，包括添加学生成绩，查询学生成绩，更新学生成绩，统计学生成绩，输出学生成绩，退出系统等功能。

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

struct student {
    char name[50];
    int roll;
    float marks;
} s;

void addRecord() {
    FILE *fptr;
    fptr = fopen("database.txt", "a");
    printf("Enter name: ");
    scanf("%s", s.name);
    printf("Enter roll number: ");
    scanf("%d", &s.roll);
    printf("Enter marks: ");
    scanf("%f", &s.marks);
    fprintf(fptr, "%s %d %.2f\n", s.name, s.roll, s.marks);
    fclose(fptr);
}

void searchRecord() {
    FILE *fptr;
    int r, flag = 0;
    fptr = fopen("database.txt", "r");
    printf("Enter roll number to search: ");
    scanf("%d", &r);
    while (fscanf(fptr, "%s %d %f\n", s.name, &s.roll, &s.marks) != EOF) {
        if (s.roll == r) {
            printf("Name: %s\nRoll number: %d\nMarks: %.2f\n", s.name, s.roll, s.marks);
            flag = 1;
        }
    }
    fclose(fptr);
    if (flag == 0) {
        printf("Record not found!\n");
    }
}

void updateRecord() {
    FILE *fptr, *fptr2;
    int r, flag = 0;
    fptr = fopen("database.txt", "r");
    fptr2 = fopen("temp.txt", "w");
    printf("Enter roll number to update: ");
    scanf("%d", &r);
    while (fscanf(fptr, "%s %d %f\n", s.name, &s.roll, &s.marks) != EOF) {
        if (s.roll == r) {
            printf("Enter new name: ");
            scanf("%s", s.name);
            printf("Enter new marks: ");
            scanf("%f", &s.marks);
            fprintf(fptr2, "%s %d %.2f\n", s.name, s.roll, s.marks);
            flag = 1;
        }
        else {
            fprintf(fptr2, "%s %d %.2f\n", s.name, s.roll, s.marks);
        }
    }
    fclose(fptr);
    fclose(fptr2);
    remove("database.txt");
    rename("temp.txt", "database.txt");
    if (flag == 0) {
        printf("Record not found!\n");
    }
}

void countRecord() {
    FILE *fptr;
    int count = 0;
    float total = 0, avg;
    fptr = fopen("database.txt", "r");
    while (fscanf(fptr, "%s %d %f\n", s.name, &s.roll, &s.marks) != EOF) {
        count++;
        total += s.marks;
    }
    fclose(fptr);
    avg = total / count;
    printf("Total students: %d\n", count);
    printf("Average marks: %.2f\n", avg);
}

void displayRecord() {
    FILE *fptr;
    fptr = fopen("database.txt", "r");
    printf("Name\tRoll\tMarks\n");
    while (fscanf(fptr, "%s %d %f\n", s.name, &s.roll, &s.marks) != EOF) {
        printf("%s\t%d\t%.2f\n", s.name, s.roll, s.marks);
    }
    fclose(fptr);
}

int main() {
    int ch;
    while (1) {
        printf("\n1. Add record\n");
        printf("2. Search record\n");
        printf("3. Update record\n");
        printf("4. Count record\n");
        printf("5. Display record\n");
        printf("6. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &ch);
        switch (ch) {
            case 1:
                addRecord();
                break;
            case 2:
                searchRecord();
                break;
            case 3:
                updateRecord();
                break;
            case 4:
                countRecord();
                break;
            case 5:
                displayRecord();
                break;
            case 6:
                exit(0);
            default:
                printf("Invalid choice!\n");
        }
    }
    return 0;
}

注意：该程序只是一个简单的示例，实际应用中还需要进行错误处理、数据验证等工作。