Names should be formed from the 26 upper and lower case letters (A .. Z, a .. z), the 10 digits (0 .. 9), and _ (underbar).

变量名应由26个大小写字母(A..Z,a..z),10个数字(0..9),和_(下划线)组成。

youdao

Swash capitals are often used with italic lower case letters.

花饰大写，通常配合斜体小写使用。

youdao

You may assume that each word will contain only lower case letters.

你可以假设每一个单词只包含小写字母。

youdao

Now, once you know each of those, you can now do 25 more upper case letters and 25 more lower case letters then there are some other stuff like punctuation and things you see on the keyboard.

一旦你知道两者中的任何一个，你就知道了另外25个,大写字母和小写字母,标点和在键盘上的,各种符号也有ASCII码。

哈佛公开课 - 计算机科学课程节选

Passwords for all accounts should be 10 characters long and include upper and lower case letters, numbers, and special characters.

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She writes it confidently and proudly, lower case letters and all.

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One of their biggest decisions, which caused upset among conservative commentators at the time, was to opt for a combination of upper and lower case letters.

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