The C++ standard library provides all the standard, generic and fundamental functions, classes and storage containers that you need in order to write non-trivial code. You could "roll your own" functions, classes and storage containers (often a useful exercise for new programmers to learn how the standard library actually works), but for experienced programmers they are an enormous time-saver and the implementations are extremely efficient.
goo bah tazzy!
With platform-dependent libraries.
To find math.h, simply include it ... #include <math.h> ... The compiler knows where the standard libraries are. This is a function of where the compiler is installed, and varies from system to system. By using the carets (< and >) you are telling the compiler to look in the "standard" places.
The header, io.h, is part of the standard C library and contains declarations for file handling and I/O functions. The file has no practical purpose in C++; it is only included because it was required prior to C++ standardisation. However, it can be used when writing C-style programs and libraries in C++.
I assume you mean using lower case letters. By convention, C and C++ standard libraries use lower-case naming conventions. This makes it easy to identify functions and types that belong to the standard library. When defining your own types, a leading capital is preferred. All capitals typically denotes a macro definition.
Platform-dependent, GUI is not part of the standard C libraries.
This will depend upon whether the applications written in C or C++ have the correct runtime libraries on the target machine. The languages themselves make no difference.
No predefined 'header' function in the standard C libraries. There are header files, if that's what you mean.
platform-dependent
That should be all you need :)
If it's a part of the standard package it has to be in visual C/Borland folder. Use search to find out exact location. In newer package standard libraries are archived, and it might tricky to find. The best way is to check the software (Microsoft, Borland, and so) producer website.
Use the C++ getline() function from the standard library.