Computer read only memory

As set out above, certain parts of computer memory are reserved exclusively for the central processor and other parts for driving any peripherals, such as a keyboard. Although this memory can be accessed (read), it cannot be changed, hence its name read-only memory (ROM). The user has... 

Many database producers provide online access to thek databases or distribute thek databases on compact disc read-only-memory (CD-ROM) and so are also considered vendors or producer/vendors. Whereas numerical growth in vendors is indicated (Fig. 1), the success of the database industry is largely a result of the transition of the information industry from paper-based to computer-based services (see Computer technology Informiation RETRIEVAL, Inforitation STORAGE MATERIALS). Thus industry growth can also be measured in terms of the increase in use of computer-readable databases as exemplified by the number of searches. 

Today, dynamic random-access memories (DRAMs) are transistor/capacitor-based semiconductor devices, with access times measured in nanoseconds and very low costs. Core memories were made of magnetic rings not less than a millimetre in diameter, so that a megabyte of memory would have occupied square metres, while a corresponding DRAM would occupy a few square millimetres. Another version of a DRAM is the read-only memory (ROM), essential for the operation of any computer, and unalterable from the day it is manufactured. We see that developments in magnetic memories involved dramatic reductions in cost and... 

Computers contain read-only memory whose contents are permanent (i.e., can only be read and not written to by the user) along with random access memory that can both be read from and written to by the user. The basic computing unit is a bit (b), which stands for binary digit 8 bits comprise a byte (B). Table 3.5 illustrates calculation of computer memory bytes, i.e., the number of locations that can be addressed. 

There are two types of memory used in computers. The main memory is based on integrated circuit chips and all parts can be accessed with great rapidity and with equal ease. In mainframe computers this is known as the main store whilst in smaller computers, including microcomputers, it is called the random access memory (RAM). Some parts of RAM may be reserved for the storage of programs or data which are to be protected from change or accidental erasure. Such a reserved area of memory is called read only memory (ROM). ROM chips, sometimes called firmware, are often used in integrators and microcomputers dedicated to particular tasks. The... 

In the years since the introduction of the first CD, the lasers and other hardware have changed significantly. We now have read-only memory discs (CD-ROMs) for the optical storage of many different kinds of data, CDs for our computers that we can... 

A starting set of permanently "wired" instructions (in read-only memory, or ROM, or "boot block") is used to start the computer, or "boot" it after a power shutdown. These instructions address a few key harware locations (in core, on disk, etc.) in which other start-up data and instructions can be accessed. If this ROM, or the all-important "boot blocks" on a hard disk, are somehow destroyed, the computer cannot be started. 

ROM ROM stands for read-only memory. It is called read-only because it can t be written to. Once the information has been written to the ROM, it can t be changed. ROM is normally used to store the computer s BIOS, because this information normally does not change. The system ROM in the original IBM PC contained the Power-On Self Test (POST), basic input-output system (BIOS), and cassette BASIC. Later IBM computers and compatibles include everything but the cassette BASIC. The system ROM enables the computer to pull itself up by its bootstraps, or boot (start the operating system). 

Most modern computers store their BIOS on an EPROM (Erasable Programmable Read Only Memory). An EPROM can be updated using flash software. In many ways, this method is more dangerous than the old-fashioned method of replacing a chip. Since the flash software overwrites the information on the chip, if you make a mistake, your computer can become unbootable. You will want to follow the instructions very carefully ... 

EEPROM Acronym for Electrically Erasable Programmable Read-Only Memory. A memory chip that maintains its contents without electrical power, and whose contents can be erased and reprogrammed either within the computer or from an external source. EEPROMs are used where the application requires stable storage without power but may have to be reprogrammed. 

ROM (read-only memory) A type of computer memory that retains its data permanently, even when power is removed. Once the data is written to this type of memory, it cannot be changed. 

CAMSEQ/M was developed around a Tektronix 4051 Microcomputer Graphics System. The hardware required includes the basic 4051 microcomputer with a minimum of 16k bytes of memory (32k is recommended), a "joystick" graphical input device, and a matrix function package (in a read-only memory firmware pack). A vastly more versatile system requires the addition of a file manager/ disk system. In order to communicate with the NIH-EPA-CIS or another "host" computer, a communications interface is necessary. The total hardware cost is approximately 17,000. Table II outlines the required hardware. The 4051 utilizes a direct view storage display which does not employ a selective erase feature. Therefore, it is necessary to replot the screen frequently in order to remove unwanted information. This handicap is the price one must pay for low cost, but quite sophisticated computer graphics features, and does not pose any major problems in CAMSEQ/M. 

RAM) and read only memory (ROM). While the processor can read the numbers stored in both kinds of memory, it can only alter the contents of RAM. The contents of ROM cannot be altered. The contents of RAM are volatile , that is, they are lost when the computer is switched off. This is not the case for ROM and so it is used to hold programs and data that the computer will always need, particularly when it is switched on again. 

Data processing. The microprocessor functions according to the program stored in the programmable read-only memory (PROM), a solid-state data-storage device whose contents is virtually indestructible. The main tasks of the 8-bit microprocessor are (a) control of the input multiplexer (b) start and control of the calibration cycle (c) correction of measured values according to the results of the calibration cycle (d) computation of periodic averages (e) calculation of output data (f) output of data and (g) control of peripherals. 

EPROM (Erasable Programable Read Only Memory)—Memory device with information placed into it during manufacture that cannot be altered with the computer. It can be erased and reprogramed with special equipment. 

Figure 1 shows a schema for an ideal distributed chemical information system. Several authors in this book refer to the need for standard interfaces. Ultimately, the personal computer will provide the graphics interface not only to personal computer databases but also to company databases running on the company mainframe, and possibly also through the same network to public hosts, so that the chemist using a personal workstation will be able to create queries which can be addressed to local files, company files and public files. Soon, chemical databases will be available on Compact Disk Read Only Memory (CD-ROM) searchable by both substructure and text. These too fit into the scheme of Figure 1. Databases such as infra-red spectra libraries will have structure-searchable components either on the personal computer or on the laboratory instrument and will also be used through the same graphical interface.

CD-ROM CD read-only memory. A device that is based on the audio compact disk and provides read-oniy access to a large amount of data (up to 640 megabytes) for use on computer systems. The term also refers to the medium in general. A CD-ROM drive must be used with the computer system to read the data from disk the data cannot normally be rewritten. Most drives can also play CD audio disks, but audio disk players can-... 

ROM Read-only memory. A form of computer memory, fabricated from integrated circuits, whose contents are permanently recorded at the time of manu cture. It is thus used to store data that never require modification. (The contents of pn ramma-ble ROM (or PROM) are recorded in a separate process after manutecture.) Like RAM it consists of an array of cells to which there is direct and extremely rapid access. 

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