在一个方形图像内至多可编码约4,000个字母数字符号，它们刚刚好可以替代那种窄的收据条。

Able to encode a maximum of about 4,000 alphanumeric characters in a square image, they lend themselves nicely to placement on a narrow receipt slip.

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在这种测试内，您给出的是一个代表某种数字符号的图像，用户必须读懂并在表单字段内输入这些符号。

In this test you present an image representing some alphanumeric characters that the user must read and type into a form field.

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