C language, type descriptor array name [constant expression] I saw it in Tan Haoqiang's book. If you have any questions, please come in.

The constant expression here simply means that you must specify the length of the array. This length must be constant at compile time.

The current C99 standard has allowed the existence of variable-length arrays, that is, the length does not need to be constant. Yes, Baidu, look at the variable-length array.