Input Unit–the “receiving” section. It obtains info from input devices & places it at the disposal of the other units for processing.
Output Unit–the “shipping” section takes information that the computer has processed & places it on various output devices to make it available for use outside the computer. (i.e.–displayed on screens, printed on paper, played on audio devices, or used to control other devices. Can also be output to networks, such as the Internet.
Memory Unit–this rapid-access, relatively low-capacity “warehouse” section retains info that has been entered through the input unit, making it immediately available for processing when needed. Also retains processed info until it can be placed on output devices by the output unit. Info in the memory is VOLATILE, it’s typically lost when the computer’s power is turned off. Often called either “memory” or “primary memory”.
Arithmetic & Logic Unit (ALU)–this “manufacturing” performs calculations, such as addition, subtraction, multiplication, & division. It contains the decision mechanisms that allow the computer to compare two items from the memory unit to determine whether they’re equal. In today’s systems, the ALU is usually implemented as part of the next logical unit, the CPU.
Central Processing Unit (CPU)–this “administrative” section coordinates & supervises the operation of the other sections. The CPU tells the input unit when info should be read into the memory unit, tells the ALU when info from the memory unit should be used in calculations & tells the output unit when to send info from the memory unit to certain output devices. Many of today’s computers have multiple CPU’s & hence, can perform many operations simultaneously–called multiprocessors. A multi-core processor implements multiprocessing on a single integrated circuit chip. ex. Dual-core has 2 CPU’s and quadcore has 4 CPUs.
Secondary Storage Unit–this is the long-term, high-capacity “warehousing” section (hard drive). Programs or data not actively being used are placed here, until they’re again needed, possibly hours, days, months or even years later. Info stored on secondary storage devices is said to be persistent (that is, it is preserved even when the computer’s power is turned off). Ex: CD’s, DVD’s, & flash drives
