Levels of Hardware

1. Machine Level: Several hardware levels are presented in machine level. These are the basic elements of computer. They are processer, input/output, main device, axuiliary storage etc. This is top level of hardware in the hardware hierarchy where user can interact with them directly.
2. Micro Progaram Level: A sequence of microinstruction constitutes the micro program. The micro program is permanently stored in Read Only Memory(ROM) and normally cannot be changed. The Program in the permanent storage is called firmwarm. micro program are written for the control unit of the modern microprocesser. each computer instruction as actually accomplished by the execution of the related micro instruction in the micro program level.
3. Digital Logic Level: Almost all basic operation of the machine are provided at this level. The basic element at this level can store, manipulate and transmit data in the form of simple binary representations. These digital logic elements are called gates. A gates is normally constricted from small number of transistors and other electronic components. Many gates are combined together to form computer subsystems like adder, subtracter, multiplexer, decoder etc in a simple IC form or in multiple IC form. The standard digital logic devices are combined together to form computer processer or computer memories.
4. Electrical and Electronic Component Level: Almost all modern computer devices are built from simple electronic components such as diode, transistors, capacitors, registor or other components in integratedcircuits (IC) form. These components rely on suitable power supplies and operating environment.