QR codes are 2-D images designed to carry alphanumeric and other information.
QR 码是一些 2-D 图像，用来携带字母数字和其他信息。
The first element of simplicity found in Twitter is the amount of information you are able to enter as data, which is limited to 140 alphanumeric characters.
Twitter中的第一个简单性元素就是您能够作为数据输入的信息的数量，该数量被限制为最多140个混合数字和字母的字符。
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