{"resolved":true,"match_type":"uuid","source_type":"original_book","book_id":"38270854-596f-4a26-8183-db8c968c6020","title":"编码 隐匿在计算机软硬件背后的语言","author":null,"edition":null,"publisher":null,"year":null,"isbn":"9787121181184","requested_by":"printed_page","book":{"source_type":"original_book","book_id":"38270854-596f-4a26-8183-db8c968c6020","id":"38270854-596f-4a26-8183-db8c968c6020","uuid":"38270854-596f-4a26-8183-db8c968c6020","title":"编码 隐匿在计算机软硬件背后的语言","normalized_title":"编码隐匿在计算机软硬件背后的语言","author":null,"edition":null,"publisher":null,"year":null,"isbn":"9787121181184","isbns":["9787121181184","0123456789","6044921875","3039331000","0000000000","0000000000000"],"parsed":true,"ai_readable":true,"document_type":"book","page_count":438,"navigation_url":"https://workshop.closeclaw.top/ai/book/38270854-596f-4a26-8183-db8c968c6020","title_url":"https://workshop.closeclaw.top/ai/title/%E7%BC%96%E7%A0%81%20%E9%9A%90%E5%8C%BF%E5%9C%A8%E8%AE%A1%E7%AE%97%E6%9C%BA%E8%BD%AF%E7%A1%AC%E4%BB%B6%E8%83%8C%E5%90%8E%E7%9A%84%E8%AF%AD%E8%A8%80","fixed_page_url_template":"https://workshop.closeclaw.top/ai/book/38270854-596f-4a26-8183-db8c968c6020/page/{printed_page}","path_api_url_template":"https://workshop.closeclaw.top/api/ai/book/38270854-596f-4a26-8183-db8c968c6020/page/{printed_page}","read_url":"https://workshop.closeclaw.top/api/ai/read/38270854-596f-4a26-8183-db8c968c6020","page_url":"https://workshop.closeclaw.top/api/ai/books/38270854-596f-4a26-8183-db8c968c6020/page","search_url":"https://workshop.closeclaw.top/api/ai/books/38270854-596f-4a26-8183-db8c968c6020/search"},"page":{"printed_page":82,"pdf_page":98,"physical_index":98,"physical_index_base":0,"printed_page_status":"recognized","page_sha256":"e22632bbdf7589ba179ccec7a1d354cdb8024155fe026457200f29846d4a82ed"},"chapter":"编码隐匿在计算机软硬件背后的语言","content":"照相机中的电路产生一个电流流入方格1，方块1通常是银色的。这支电流有可能流经（也可能未流经）方格2\\~6上的5个触点，这取决于方格是纯银还是涂有颜料的。这样，如果照相机在触点4和触点5上检测到了电流，而在触点2、3和6上却没有检测到，那么这个胶片的速度就是400ASA。这样，照相机就可以据此来调整胶片的曝光时间了。\n\n假设胶片速度是50、100、200或400ASA，那么廉价的相机就只需读取方格2和方格3上的电流。\n\n多数照相机不需要读取或使用方格8\\~12。方格8、9和10被用来对这卷胶卷进行编码，方格11和方格12指出曝光范围（exposurelatitude)，这取决于胶片是用于黑白冲洗、彩色冲洗，还是做彩色幻灯片。\n\n也许最常见的二进制数的表现形式就是无所不在的通用产品代码（UPC，UniversalProduct Code)，这个小条形码出现在差不多我们日常所购买的所有商品的包装上。UPC已经成为计算机逐步进入人们日常生活的标志之一。\n\n尽管UPC经常会使人们瞎猜疑，但是它其实是无辜的。使用它的初衷仅仅是为了实现零售业的结算和存货管理的自动化，而且它在这方面的应用也很成功。当UPC与一个设计精巧的结账系统结合使用时，顾客会得到一张逐项开列的消费清单，这点是传统的现金出纳员所无法做到的。\n\n有趣的是，UPC也是二进制码，尽管乍看起来它并不太像。将UPC解码并看看UPC到底是怎样工作的，就明白了。\n\n在最常见的形式中，UPC是由30条不同宽度的垂直黑色条纹组成的，它们的间隔宽度也不同，条纹下面标有数字。例如，以下是Campbell公司出品的103/4盎司的罐装鸡汁面汤包上的UPC。\n\n编码隐匿在计算机软硬件背后的语言\n\n82","previous_page":81,"next_page":83}