Hardware refers to the physical components of a computer, the ones you can touch. Examples include the keyboard, the monitor, the printer.
A header file is a file that contains class interface definitions and/or global function declarations. By convention, header files have the extension .h.
The heap is the area of memory where variables of the dynamic storage class store their data.
Hex is an abbreviation for hexadecimal.
A hexadecimal number system 16 digits, 0-9 and a-f.