{"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":319,"pdf_page":335,"physical_index":335,"physical_index_base":0,"printed_page_status":"recognized","page_sha256":"af2778b50b5f9b259a0faccb938b0a4254f58580f842197d4a80929c9ca32e80"},"chapter":"编码隐匿在计算机软硬件背后的语言","content":"一个EBCDIC字符码由8位比特组成，进一步可以细分为高半字节（4比特）与低半字节。低半字节是BCD码，与字符的数字穿孔保持一致，高半字节与区域穿孔的编码保持一致（而且与区域穿孔一一对应)。回忆一下第19章的BCD编码原理，其本质是采用二进制数对十进制数进行编码（binary-coded decimal)—其中数字0\\~9都利用不同的4位二进制数进行编码。\n\n数字0\\~9并不需要区域穿孔进行额外表示，它们的EBCDIC编码的高半字节是1111，代表了区域穿孔不起作用，而0\\~9的EBCDIC编码的低半字节是数字穿孔的BCD码，如下所示。\n\n大写字母有一些有趣的规律，如果区域穿孔只出现在第12行，则高半字节标识为1100；如果只出现在第11行，则高半字节标识为1101；如果出现在第0行，则高半字节标识1110。下表给出了大写字母及其对应的EBCDIC编码。\n\n20 ASCII 码和字符转换\n\n319","previous_page":318,"next_page":320}