How a process is created?

Difficulty: unrated

Answer

The OS is reading program's code and any additional relevant data
Program's code is loaded into the memory or more specifically, into the address space of the process.
Memory is allocated for program's stack (aka run-time stack). The stack also initialized by the OS with data like argv, argc and parameters to main()
Memory is allocated for program's heap which is required for dynamically allocated data like the data structures linked lists and hash tables
I/O initialization tasks are performed, like in Unix/Linux based systems, where each process has 3 file descriptors (input, output and error)
OS is running the program, starting from main()