数据存储 Storage

Grade 2 ( 5-7岁 ) 要掌握的程度

Computers store data that can be retrieved later. Identical copies of data can be made and stored in multiple locations for a variety of reasons, such as to protect against loss.

For example, pictures can be stored on a cell phone and viewed later, or progress in a game can be saved and continued later. The advantage of recording data digitally, such as in images or a spreadsheet, versus on a physical space, such as a whiteboard, is that old data (states of data collected over time) can be easily retrieved, copied, and stored in multiple places. This is why personal information put online can persist for a long time. Understanding local versus online storage is not expected at this level.

Crosscutting Concepts: System Relationships; Privacy and Security Connections Within Framework: K–2.Impacts of Computing.Social Interactions; K–2.Algorithms and Programming.Variables

计算机存储数据, 是为了方便之后调用. 比如说, 图片存储在手机上, 以后就可以调用查看. 比如游戏进度被保存下来后, 下次就不用从头开始.

之所以要在多个地方备份同一个文件, 有多种考虑, 一种是为了防止数据意外丢失.

相对于在物理硬件上保存数据(比如在白板上书写), 以电子数字的方式保存数据(比如电子图片或者电子表格)的好处是, 旧的数据可以很容易地被检索、复制、并拷贝存储在多个地方. 这就是为什么放在网上的个人信息可以保存很长时间的原因.

对于这个阶段的学生, 不需要理解本地存储和在线存储的细节.

Grade 5 ( 8-11岁 ) 要掌握的程度

Different software tools used to access data may store the data differently. The type of data being stored and the level of detail represented by that data affect the storage requirements.

Music, images, video, and text require different amounts of storage. Video will often require more storage than music or images alone because video combines both. For example, two pictures of the same object can require different amounts of storage based upon their resolution. Different software tools used to access and store data may add additional data about the data (metadata), which results in different storage requirements. An image file is a designed representation of a real-world image and can be opened by either an image editor or a text editor, but the text editor does not know how to translate the data into the image. Understanding binary or 8-bit versus 16-bit representations is not expected at this level.

Crosscutting Concept: System Relationships Connections Within Framework: 3–5.Computing Systems.Hardware and Software; 3–5.Algorithms and Programming.Variables

不同的软件工具可能以不同的方式存储数据. 被存储的数据类型和该数据所代表的详细程度会反过来影响存储要求.

音乐文件、图像文件、视频文件、文本文件需要不同的存储空间. 视频通常需要比音乐和图像更多的存储空间, 因为视频同时结合了音乐和图像. 比如同一物体的两张图片, 根据其分辨率需要不同的存储空间.

访问和存储数据的软件工具可能会额外添加一些数据(元数据), 从而带来不同的存储要求. 比如说, 图像文件是现实世界图像表示, 尽管可以用图像编辑器或者文本编辑器打开, 但是文本编辑器无法将数据转化为图像.

这个阶段的学生不需要理解二进制、八进制、十六进制的表示方法.

Grade 8 ( 11-14岁 ) 要掌握的程度

Applications store data as a representation. Representations occur at multiple levels, from the arrangement of information into organized formats (such as tables in software) to the physical storage of bits. The software tools used to access information translate the low-level representation of bits into a form understandable by people.

Computers can represent a variety of data using discrete values at many different levels, such as characters, numbers, and bits. Text is represented using character encoding standards like UNICODE, which represent text as numbers. All numbers and other types of data are encoded and stored as bits on a physical medium. Lossy and lossless data formats are used to store different levels of detail, but whenever digital data is used to represent analog measurements, such as temperature or sound, information is lost. Representations, or file formats, can contain metadata that is not always visible to the average user. There are privacy implications when files contain metadata, such as the location where a photograph was taken.

Crosscutting Concept: Abstraction Connections Within Framework: 6–8.Algorithms and Programming.Variables; 6–8.Networks and the Internet.Network Communication and Organization

应用程序将数据存储为特定的形式, 这种形式包括有组织的格式(比如表格)到比特^[1]的物理存储. 软件工具将抽象的比特信息转化成人们可以理解的形式.

计算机使用不同层次的离散值来表示各种数据, 包括字符、数字、比特. 文本用Unicode这样的字符编码来表示, 它将文本转化为数字. 所有数据类型都被编码并作为比特存储在物理介质上.

有损和无损的数据格式被用来存储不同级别的数据细节, 但是只要使用数字信号表示模拟信号(比如温度、声音), 信息就必然会有丢失.

文件格式可能包含一些元数据, 这些元数据对于普通用户来说通常是不可见的. 文件的元数据会带来隐私安全问题, 比如说照片文件的元数据中会泄漏拍摄的地点.

Grade 12 ( 14-18岁 ) 要掌握的程度

Data can be composed of multiple data elements that relate to one another. For example, population data may contain information about age, gender, and height. People make choices about how data elements are organized and where data is stored. These choices affect cost, speed, reliability, accessibility, privacy, and integrity.

A data model combines data elements and describes the relationships among the elements. Data models represent choices made about which data elements are available and feasible to collect. Storing data locally may increase security but decrease accessibility. Storing data on a cloud-based, redundant storage system may increase accessibility but reduce security, as it can be accessed online easily, even by unauthorized users. Data redundancies and backups are useful for restoring data when integrity is compromised.

Crosscutting Concepts: System Relationships; Privacy and Security; Communication and Coordination Connection Within Framework: 9–12.Algorithms and Programming.Algorithms

数据可以由相互关联的多个数据元素组成. 比如说, 人口数据可能包含年龄、性别、身高的信息.

人们需要对数据元素的组织方式和数据的存储位置做出选择, 这些选择会影响成本、速度、可靠性、可访问性、隐私、完整性.

一个数据模型结合了数据元素并描述了元素之间的关系. 不同的数据模型代表不同的选择 -- 选择哪些数据元素是可用的、可收集的. 在本地存储数据可能会提高安全性, 但是会降低可访问性. 在云端存储数据可能会提高可访问性, 但是会降低安全性, 因为它可以轻易地被在线访问, 甚至是被未经授权的用户访问. 对数据进行冗余备份, 对于防范数据丢失是很有用的.

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1. "比特"是英语“bit”的音译, “bit”是“binary digit“的意思, 即”二进制数字“. 1个比特就表示1位二进制数字 ↩︎