<cstdlib>

Question

According to its definition , it is used in dynamic memory and random number generation but in the earlier programs where dynamic memory was included why <cstdlib>as a header was not used ?

Answer 1

You might be talking about the C++ 'new' keyword when you referenced 'dynamic memory'. <cstdlib> provides malloc, calloc, which are used in C for dynamic memory allocation.

http://www.cplusplus.com/reference/cstdlib/malloc/