{"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":340,"pdf_page":356,"physical_index":356,"physical_index_base":0,"printed_page_status":"recognized","page_sha256":"e3db5121f005b5585828d871d9f7b3bac802d3fced0597c8266c261d67e3c33c"},"chapter":"编码隐匿在计算机软硬件背后的语言","content":"计算机的键盘有100多个按键，但类似于打字机的键盘可能只有48个按键。\n\n如果要让连接到计算机上的键盘能正常工作的话，就需要配备一些硬件来为每个按键提供唯一的代码，以便区分哪一个按键被按下了。假定这个代码就是按键的ASCI码，这样可行吗？你的答案或许是肯定的，但要设计出能识别ASCI码的硬件却是不切实际的。举例来说，键盘上的按键A对应的ASCI码可能是41h，也可能是61h，具体是哪个，还取决于用户是否按下了Shift键；另外，现在计算机键盘上有很多的按键并没有ASCII码与之对应。我们称键盘硬件提供的代码为扫描码（scan code)。当按下键盘上的某个按键时，一小段计算机程序就会计算出这个按键对应的ASCI码（如果有的话）。\n\n这里为了避免键盘硬件的电路图太复杂，假设键盘上只有16个按键。任何一个按键被按下，键盘硬件就会产生一个4位的代码，二进制数值范围是0000到1111。\n\n键盘硬件包含了一些前面曾讲过的部件，如下图所示。\n\n编码隐匿在计算机软硬件背后的语言\n\n340","previous_page":339,"next_page":341}