1．录入几位学生信息（姓名，学号，饭卡余额），并保存到student.txt文件中；2．能够依据学号对饭卡充值，每次充值的金额为10的倍数；3．能够按照学号查询饭卡余额，如果谁的余额少于10元，就给出充值提示。要求：软件至少应具有“输入初始数据”、“饭卡充值”、“查询余额”、“退出”4项菜单。

好的，下面是Python代码实现：

# 定义学生类
class Student:
    def __init__(self, name, id, balance):
        self.name = name
        self.id = id
        self.balance = balance

    # 返回学生信息字符串
    def __str__(self):
        return f"{self.name}\t{self.id}\t{self.balance}\n"

# 读取学生信息文件
def read_students(filename):
    students = []
    with open(filename, "r") as file:
        lines = file.readlines()
        for line in lines:
            name, id, balance = line.strip().split("\t")
            student = Student(name, id, int(balance))
            students.append(student)
    return students

# 保存学生信息文件
def save_students(filename, students):
    with open(filename, "w") as file:
        for student in students:
            file.write(str(student))

# 根据学号查询学生
def find_student(students, id):
    for student in students:
        if student.id == id:
            return student
    return None

# 录入学生信息
def input_students(students):
    name = input("请输入学生姓名：")
    id = input("请输入学生学号：")
    balance = int(input("请输入学生饭卡余额："))
    student = Student(name, id, balance)
    students.append(student)

# 饭卡充值
def recharge_balance(students):
    id = input("请输入学生学号：")
    student = find_student(students, id)
    if student:
        amount = int(input("请输入充值金额（10的倍数）："))
        if amount % 10 == 0:
            student.balance += amount
            print(f"充值成功，当前余额为{student.balance}元。")
        else:
            print("充值金额必须为10的倍数！")
    else:
        print("该学生不存在！")

# 查询余额
def check_balance(students):
    id = input("请输入学生学号：")
    student = find_student(students, id)
    if student:
        print(f"{student.name}的饭卡余额为{student.balance}元。")
        if student.balance < 10:
            print("余额不足，请及时充值！")
    else:
        print("该学生不存在！")

# 主函数
def main():
    filename = "student.txt"
    students = read_students(filename)
    while True:
        print("请选择操作：")
        print("1. 输入初始数据")
        print("2. 饭卡充值")
        print("3. 查询余额")
        print("4. 退出")
        choice = input("请输入序号：")
        if choice == "1":
            input_students(students)
            save_students(filename, students)
        elif choice == "2":
            recharge_balance(students)
            save_students(filename, students)
        elif choice == "3":
            check_balance(students)
        elif choice == "4":
            print("谢谢使用，再见！")
            break
        else:
            print("输入有误，请重新输入！")

# 运行主函数
if __name__ == "__main__":
    main()

在主函数中，首先读取student.txt文件的学生信息，然后进入一个循环，根据用户输入的选择执行相应的操作，最后保存学生信息并退出程序。