is the usage of wildcard and firstword in makefile?

In a Makefile, a wildcard is a special character that matches any number of characters in a filename. The `wildcard` function can be used to find all files that match a particular pattern. For example, the following line will find all files in the current directory that end with ".c":

SOURCES := $(wildcard *.c)

The `firstword` function, on the other hand, is used to extract the first word from a string. This is often used in Makefiles to extract the first word from a list of space-separated values. For example, the following line extracts the first word from the `SOURCES` variable defined above:

FIRST_SOURCE := $(firstword $(SOURCES))

This would set the `FIRST_SOURCE` variable to the name of the first C file in the current directory.