anyone ,can you explain?
What is library functions?
In your own knowledge.
It is a function (or a class foor OOP) that is pulled into your program from a collection, available on the system your program runs on. Usually (not always) these collections are physically realised as files, with a given extension (.dll, .so, .jar, .a, .lib..) each containing tens of functions/classes.
Also the way functions are “pulled into” differs: functions may be physically copied into the executable (static linkage) or loaded in memory at run time (called dynamic linkage in some contexts), by way of an OS component (loader) or of the interpreter itself. Some runtimes (e.g. java) can allow you to pull them from remote network repositories (scary).
Most - if not all - modern environments are equipped with so-called “standard libraries”, which are part of the official description of the language (and sometimes referred to as “the runtime”) , which are sometimes very extensive. (e.g the standard C library, C++’s stl - standard template library). In addition, one can avail himself of third-party libraries, or develop his own.