Program or a set of programs is known as Software. Now, What is program? Program is a instruction or set of instructions. So, we can say Computer Programs, namely, the list of instructions to be executed by a computer are known as the software of a computer. The electronic circuits used in building the computer that executes the software is known as hardware of a computer. It refers to the physical devices of a computer system, such as Input devices, storage devices, processing unit, control unit , and output devices. A hardware is linked together with software to form a effective working unit that is a computer system. To take analogy, a home television set bought from a shop is hardware; the various entertainment programs transmitted from the television station are its software. It is immediately evident that hardware is necessary but software is vital. What is the use of a home television set if the programs not transmitted by television station. Another important point brought out by this analogy is that software production is difficult and expensive. Hardware is one-time expense whereas software is a recurring expense.
Thus, there is a special relationship between hardware and software. Both are complementary to each other. Hardware is nothing without software and vice-versa. By very simple example, these two can be described as both a notebook and a pen are hardware and the written material on notebook is software.