Large System

It is impossible to know how minicomputers and mainframes are related to one another. The difference lies in their processing ability and the capacity of their primary storage. Microcomputers are the smallest, with a primary storage range of 4 to 64 K bytes, as well as the slowest, while minicomputers have a primary storage range 16 to 512 K bytes and greater processing speed. Mainframes are the fastest and can have over 1 M bytes in primary storage. They are commonly used in time sharing systems.

In a time sharing system, many companies log on to the same computer via telephone lines. To do this, a modem should be installed. A modem enables a computer to transmit data over telephone lines. A telephone line used only for data communication is called distributed data processing. The opposite concept – a centrally located computer system – is called centralized data processing.

With distributed data processing, the branch communities with the CPU via a terminal. A terminal located away from the CPU is referred to as a remote device. It can be a visual display or hard copy terminal connected by telephone lines; but it can also be a secondary storage device or even a card reader, that is an input device that transfers data from punched cards to primary storage.

In this case, punch cards are coded in Hollerith code and contain 80 columns in which holes can be punched. There are twelve rows in each column. The pattern of holes in the column determines the character being represented. The holes are punched with a key punch which has a keyboard similar to that of a typewriter. However, only 80 characters can be recorded in a card reader. Of course it is very slow process of input devices; however, for batch processing, it is considered a very useful method of input.

In this respect, supermarkets often use a similar method with which a Universal Product Code (CPU) is printed on a label. The CPU includes information, such as the product, the manufacturer and the price. All of that information from the label. It is in fact a terminal which can be used to keep inventory.

Answer the following questions based on the text above!
1. What is the primary storage range of microcomputers?
2. What is commonly used in time sharing systems?
3. What can a modem do?
4. What is meant by dedicated line?
5. What is the difference between “distributed data processing” and centrally located computer system?
6. How are punched cards coded?
7. Why can only 80 characters be recorded on a punched card?
8. What is CPU?