SUMMARY

Now that you have finished chapter 2, you should be feeling more at ease with digital computers. You should realize by now that they are not so hard to understand, once you have the terminology down. The information that follows summarizes the important points of this chapter.

The CENTRAL PROCESSING UNIT is the brain of the computer. We generally refer to it as the cpu or mainframe.

The CONTROL SECTION directs the flow of traffic (operations) and data, and maintains order within the computer.

The ARITHMETIC-LOGIC SECTION performs all arithmetic operations-adding, subtracting, multiplying, and dividing. It also tests various conditions during processing and takes action based on the result.

INTERNAL STORAGE is sometimes referred to as primary storage, main storage, or main memory (because its functions are similar to our own human memory). It stores the programs and data.

MAGNETIC CORE STORAGE is made up of tiny doughnut-shaped rings made of ferrite (iron) that are strung on a grid of very thin wires.

SEMICONDUCTOR STORAGE consists of hundreds of thousands of tiny electronic circuits etched on a silicon chip.

BUBBLE STORAGE is made of semiconductor material in the form of a very thin crystal.

READ-ONLY MEMORY (ROM) allows us to permanently store programs that will not be lost even when the computer is powered down.

RANDOM-ACCESS MEMORY (RAM) is read/ write memory. It is the working memory, rather like a blackboard, that you can scribble down notes, read them, and rub them out when you are finished with them.

SECONDARY STORAGE is the memory outside the main body of the computer (cpu) where we store programs and data for future use.

MAGNETIC TAPE is a sequential access storage device.

MAGNETIC DISK is a direct access storage device.

INPUT/OUTPUT DEVICES are the means by which the computer communicates with the outside world. These include magnetic tape units, magnetic disk drive units, floppy disk drive units, printers (daisy-wheel, dot-matrix, ink jet, and laser), and display devices (raster scan crt and flat panel).