Keyboard: An input device on which characters are represented as discrete keys. When a key is pressed, the associated character is input to the computer system.
键盘：一种输入设备，它上面的字符是用一些相分离的键表示的，当一个键按下时，相应的字符就被送入到计算机系统中。
The more different the character set size and the input device capability are, the more complicated the input method becomes.
字符集的大小和输入设备的能力之间差别越大，输入法就需要变得越复杂。
The character image from the input device must be preprocessed to filter noises and enhance useful information.
为了滤除噪声，增强有用信息，经输入设备输入的字符图像一般需做预处理。
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