When software is installed onto a modern day personal computer (most commonly from a CD-ROM, though other media or downloading from the internet is also common), code comprising the program and any associated files is stored on the hard drive. This code comprises of a sequence of instructions for performing designated tasks, and data associated with these instructions. The code remains there until the user chooses to execute the program in question, on which point sections of the code are loaded into the computer’s memory.
The CPU then executes the program from memory, processing every instruction in turn. Certainly, in order to execute the instructions, it is necessary for the CPU to understand what the instruction is telling it to do. Consequently, recognition for instructions that could be encountered requires to be programmed into the processor. The instructions that can be recognized by a processor are referred to as an ''instruction set'',
Once the instruction has been recognized, and the actions that should be carried out are decided upon, the actions are then performed before the CPU continues on to the next instruction in memory. This process is called the ''instruction execution cycle'',
Results can then be accumulated back in the memory, and later saved to the hard drive and perhaps backed up onto removal media or in separate locations