#define uchar unsigned char: Defining an Unsigned Character Data Type

This line of code is a preprocessor directive that defines the data type 'uchar' as an 'unsigned char'. This means that any time 'uchar' is used in the code, it will be interpreted as an 'unsigned char'.

'unsigned' means that the variable can only take on positive values, while 'char' is a data type that represents a single character (such as a letter, number, or symbol) in the ASCII character set. Therefore, 'uchar' can be used to represent a single character value that is positive and does not exceed 255.