use of undeclared identifier "CLK_TCK"

The identifier "CLK_TCK" is a constant that represents the number of clock ticks per second. It is a legacy identifier that was used in older versions of C and is no longer part of the standard C library.

If you are using "CLK_TCK" in your code and getting an error message that says "use of undeclared identifier," it means that the compiler does not recognize the identifier. To resolve this issue, you can define "CLK_TCK" yourself as follows:

#define CLK_TCK CLOCKS_PER_SEC

This will define "CLK_TCK" as the number of clock ticks per second, which is equivalent to the "CLOCKS_PER_SEC" constant provided by the standard library.