Vocabulary:

1) Hardware - the mechanical, magnetic, electronic and electrical devices or components of a computer.

2) Software - programs which control the operation of computer hardware and the associated documentation, etc., needed to do so.

Text 3.8 The Types of Memory

Pre-Reading Task:

1. Describe the recent level of technology development.

2. What types of memory do you know?

3. Read the text “The Types of Memory” and make a list of different types of a microcomputer memory.

In all types of computer systems, from a small dedicated microprocessor system to the largest full size computer, memory plays a very essential part. The memory section of the microcomputer system serves the purpose of holding either information, that the computer will need, or information, that the computer has already generated, which will be utilized in the future. In other words, the memory of a microcomputer is used for storing the program and the data. There are two basic types of memory, namely read/write memory whose contents can be altered by writing new information into it and read-only memory (ROM) whose contents are fixed. Read/write memory is usually exclusively referred to as random-access memory (RAM) for historical reasons, although strictly speaking most modern read-only memories can also be accessed in a random order and therefore qualify for such a description. Random means that any one of the different memory locations can be written into or read from with equal ease and that it takes the same amount of time to address any one of the different memory locations within the same device.

The semiconductor RAM memory is of the volatile type. That is, when power is removed, all information previously written in memory is lost.

A problem develops because memory needs to have both non-volatility and read/write capability. At the time of this writing, there is not one RAM chip that has both of these desirable functions. The memory chips are either of the RAM family and have the read/write capability but are volatile or of the ROM family and have only the read capability but are non-volatile. So the read/write feature of the RAM makes it a very versatile memory device. However, its volatility presents a special problem.

Recently, technology has advanced to the stage where nonvolatile RAM's can be made. These do not lose their information when the power in them is interrupted.

The next generation of semiconductor RAM memories has advanced to higher density (more memory cells/chip) and higher operating frequencies.

The essential difference as far as the user is concerned is that ROM retains the information in it even without power, even if a program error or other fault causes the system to try and overwrite the contents of the ROM. It is therefore used mainly for storing fixed programs and constants.

As the term ROM implies, this type of memory can only be read from and not written into by the user.

Since the ROM has the feature of nonvolatility, it lends it self to applications such as dedicated subroutines including mathematical packages, monitor¹ programs, debug² programs and any program that has a fixed structure where there is no need to make changes to the program that resides in the ROM.