{"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":80,"pdf_page":96,"physical_index":96,"physical_index_base":0,"printed_page_status":"recognized","page_sha256":"3bfb295a11b260f032b1750a72a1123c12eff2f390efc7f9f1988136a32ef922"},"chapter":"编码隐匿在计算机软硬件背后的语言","content":"比特通常无法从日常观察中找到，它深藏于电子设备中。我们看不到压缩磁盘(CD)、数字手表或计算机中被编码的比特，但有时比特也会清晰地呈现在我们眼前。\n\n下面就是一个例子。如果你有一台相机是使用35毫米胶片的，观察一下它的卷轴。这样拿住胶卷：\n\n你可以看到像国际象棋棋盘那样银黑交错排列的方格，这些方格在图中已经用数字1\\~12进行了标注。这叫做DX编码，这12个方格实际上是12个比特位。一个银色的方格代表值为1的比特，一个黑色的方格代表值为0的比特。方格1和方格7通常是银色的（代表1)。\n\n这些比特代表什么意思呢？你可能会知道，有些胶片比其他胶片对光更敏感些。这种对光的敏感程度称做胶片速度。人们会说某种对光非常敏感的胶片“很快”，那是因为这种胶片的曝光速度极快。胶片的曝光速度是由美国标准协会 ASA（American StandardsAssociation）来制定等级的。最常用的等级有100、200和400。ASA等级不仅以十进制数字的形式印在胶卷的外包装和暗盒上，它还以比特的形式进行了编码。\n\n胶卷总共有24个ASA等级，它们是：\n\n编码—隐匿在计算机软硬件背后的语言\n\n80","previous_page":79,"next_page":81}