What are the rules for comparing strings in the C language?

In C programming language, the comparison rule for strings is based on lexicographical order. More specifically, when comparing two strings, the ASCII values of the characters at each position are compared one by one.

The comparison process is as follows:

1. Compare the ASCII values of the first character of two strings. If they are different, the smaller character comes first and the larger character comes later.
2. If the first characters of two strings are the same, then continue comparing the second characters, and so on, until all characters of one of the strings have been compared.
3. If two strings are identical, they are considered equal.
4. If all characters in one string are smaller than those in another string, consider the smaller string to come before the larger string.

It is important to note that the string comparison function strcmp() in the C language can be used to compare the size of two strings. The return value of 0 indicates that the two strings are equal, less than 0 indicates that the first string is less than the second string, and greater than 0 indicates that the first string is greater than the second string.