An essential component of a computer is the memory which it uses to hold data currently being used by the processor. This is the random access memory (RAM), the computer's working memory in which programs and data are stored so that they can be accessed very quickly by the processor. The processor stores data in RAM and retrieves data from it as it carries out its manipulations. The more RAM a computer has, the faster the computer programs will run. RAM memory is used and reused and any data held in RAM is normally lost when the computer is turned off.
To ensure that essential data is not lost when the computer is switched off, all personal computers have a hard disk (sometimes called a hard drive) which can store data permanently. Part of the starting-up process of a computer is to copy start-up programs and data from the hard disk into the RAM, and all important data in the RAM is copied to the hard disk during the closing-down process. I'll discuss hard disks in more detail in Section 12.
There are other important components needed to make a modern computer work effectively, but the ones I've mentioned will suffice to illustrate the main ICT processes involved in a computing system.