C++ on Linux not recognizing commands like exit() and printf()

Specifically for ‘exit’ was not declared in this scope all you need is:

#include <stdlib.h>

In terminal :- when you write man exit :- it will show

   exit - cause normal process termination

SYNOPSIS #include stdlib.h

   void exit(int status);

so you required to define header #include stdlib.h

Recent versions of GCC have gotten stricter in what responsibilities the programmer needs to fulfill. Include the cstdlib, cstdio, etc. header and access these functions from the std namespace.