HARDWARE: The physical components of the system. The things you can see and touch. Hardware includes input, processing, storage and output devices.

Function: An activity or sequence of activities carried out by a device or person. Their purpose being to carry out this function. (Different to the programming language meaning). 

There are essentially five functions performed by hardware devices: 

• Input puts data into the computer in a form ready for processing
• Output takes the processed data and makes it available to people or other systems
• Processing works with the data to achieve the purpose of the system
• Control coordinates the activities of all the components of the computer system
• Storage keeps data for later use by the computer

These five basic hardware functions combine to perform all the actions of all computer systems

In brief, input is received from outside the system and processed into output. This processing may involve reading and/or writing to storage. Control is the function that coordinates the sequencing and timing of the other functions. 

Fig 2.5 illustrates the flow of data between each of these functions. Notice that control is positioned within the processing function. Control is a form of processing that directs every other function. Data is not moved or processed by control functions, rather other functions are instructed to commence their actions.