When we look at the physical parts of a computer we term it as computer hardware. These include the basic monitor, keyboard, mouse and the Central operating System (CPU) in its simplest form, Computer hardware can be classified into for categories

Input Devices

This are normally those devices that are used to input into the computer. They include keyboard and the mouse. Without these, there will be no way to interact with the computer and give it instructions on what you intend of it to do.
Storage Devices
Storage devices are basically devices that are used to store data. They are further classified in two depending on the location:
Primary Storage Devices: These are mainly those devices that the computer cannot do without when it comes to storage. An example is the hard disk. This type of storage is the first choice storage device in any computer.
Secondary Storage Devices: These are storage devices that normally come as accessories to the computer. They include external hard disk, Compact Disk (CD) Dive and Digital Video Drive (DVD) drive. Normally these devices are attached to the computer and are used to store information that are to be kept in a different location as the computer.

Internal Components

Finally for all computers to function, apart from the hardware that is visible to the eyes, there are internal components that are fundamental to the functioning and are not visible to the eyes. These include components like the RAM, Central Processing Unit.

Conclusion

In conclusion, the computer hardware are the physical components of the machine. It is good to note that these components must function hand in hand with computer software in order to get the most functionality of the computer. Unlike Computer software, Computer Hardware are normally a one off expense and once purchased, they will serve for a long time if while designing applications.