Where rom can be used in the computer?

• Computers. A computer's ROM stores the basic input-output system (BIOS) information.
• Video games. ROM features video game technology in gaming consoles and games for systems that use cartridges.
• Smartphones.
• Digital speed meters.
• Programmable electronics.
• ROM.
• Programmable ROM.
• Mask ROM.

Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing software that is rarely changed during the life of the system, also known as firmware. Software applications (like video games) for programmable devices can be distributed as plug-in cartridges containing ROM.

Strictly speaking, read-only memory refers to memory that is hard-wired, such as diode matrix or a mask ROM integrated circuit (IC), which cannot be electronically[a] changed after manufacture. Although discrete circuits can be altered in principle, through the addition of bodge wires and/or the removal or replacement of components, ICs cannot. Correction of errors, or updates to the software, require new devices to be manufactured and to replace the installed device.

Floating-gate ROM semiconductor memory in the form of erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM) and flash memory can be erased and re-programmed. But usually, this can only be done at relatively slow speeds, may require special equipment to achieve, and is typically only possible a certain number of times.[1]

The term "ROM" is sometimes used to refer to a ROM device containing specific software or a file with software to be stored in a writable ROM device. For example, users modifying or replacing the Android operating system describe files containing a modified or replacement operating system as "custom ROMs" after the type of storage the file used to be written to, and they may distinguish between ROM (where software and data is stored, usually Flash memory) and RAM.

IBM used capacitor read-only storage (CROS) and transformer read-only storage (TROS) to store microcode for the smaller System/360 models, the 360/85, and the initial two System/370 models (370/155 and 370/165). On some models there was also a writeable control store (WCS) for additional diagnostics and emulation support. The Apollo Guidance Computer used core rope memory, programmed by threading wires through magnetic cores.

The simplest type of solid-state ROM is as old as the semiconductor technology itself. Combinational logic gates can be joined manually to map n-bit address input onto arbitrary values of m-bit data output (a look-up table). With the invention of the integrated circuit came mask ROM. Mask ROM consists of a grid of word lines (the address input) and bit lines (the data output), selectively joined together with transistor switches, and can represent an arbitrary look-up table with a regular physical layout and predictable propagation delay. Mask ROM is programmed with photomasks in photolithography during semiconductor manufacturing. The mask defines physical features or structures that will be removed, or added in the ROM chips, and the presence or absence of these features will represent either a 1 or a 0 bit, depending on the ROM design. [2] Thus by design, any attempts to electronically change the data will fail, since the data is defined by the presence or absence of physical features or structures that cannot be electronically changed. For every software program, even for revisions of the same program, the entire mask must be changed, which can be costly.

In mask ROM, the data is physically encoded in the circuit, so it can only be programmed during fabrication. This leads to a number of serious disadvantages:

Subsequent developments have addressed these shortcomings. Programmable read-only memory (PROM), invented by Wen Tsing Chow in 1956,[3][4] allowed users to program its contents exactly once by physically altering its structure with the application of high-voltage pulses. This addressed problems 1 and 2 above, since a company can simply order a large batch of fresh PROM chips and program them with the desired contents at its designers' convenience.

The advent of the metal–oxide–semiconductor field-effect transistor (MOSFET), invented at Bell Labs in 1959,[5] enabled the practical use of metal–oxide–semiconductor (MOS) transistors as memory cell storage elements in semiconductor memory, a function previously served by magnetic cores in computer memory.[6] In 1967, Dawon Kahng and Simon Sze of Bell Labs proposed that the floating gate of a MOS semiconductor device could be used for the cell of a reprogrammable ROM, which led to Dov Frohman of Intel inventing erasable programmable read-only memory (EPROM) in 1971.[7] The 1971 invention of EPROM essentially solved problem 3, since EPROM (unlike PROM) can be repeatedly reset to its unprogrammed state by exposure to strong ultraviolet light.

Electrically erasable programmable read-only memory (EEPROM), developed by Yasuo Tarui, Yutaka Hayashi and Kiyoko Naga at the Electrotechnical Laboratory in 1972,[8] went a long way to solving problem 4, since an EEPROM can be programmed in-place if the containing device provides a means to receive the program contents from an external source (for example, a personal computer via a serial cable). Flash memory, invented by Fujio Masuoka at Toshiba in the early 1980s and commercialized in the late 1980s, is a form of EEPROM that makes very efficient use of chip area and can be erased and reprogrammed thousands of times without damage. It permits erasure and programming of only a specific part of the device, instead of the entire device. This can be done at high speed, hence the name "flash".[9][10]

All of these technologies improved the flexibility of ROM, but at a significant cost-per-chip, so that in large quantities mask ROM would remain an economical choice for many years. (Decreasing cost of reprogrammable devices had almost eliminated the market for mask ROM by 2000.) Rewriteable technologies were envisioned as replacements for mask ROM.

The most recent development is NAND flash, also invented at Toshiba. Its designers explicitly broke from past practice, stating plainly that "the aim of NAND flash is to replace hard disks,"[11] rather than the traditional use of ROM as a form of non-volatile primary storage. As of 2021[update], NAND has nearly completely achieved this goal by offering throughput higher than hard disks, lower latency, higher tolerance of physical shock, extreme miniaturization (in the form of USB flash drives and tiny microSD memory cards, for example), and much lower power consumption.

Many stored-program computers use a form of non-volatile storage (that is, storage that retains its data when power is removed) to store the initial program that runs when the computer is powered on or otherwise begins execution (a process known[b] as bootstrapping, often abbreviated to "booting" or "booting up"). Likewise, every non-trivial computer needs some form of mutable memory to record changes in its state as it executes.

Forms of read-only memory were employed as non-volatile storage for programs in most early stored-program computers, such as ENIAC after 1948. (Until then it was not a stored-program computer as every program had to be manually wired into the machine, which could take days to weeks.) Read-only memory was simpler to implement since it needed only a mechanism to read stored values, and not to change them in-place, and thus could be implemented with very crude electromechanical devices (see historical examples below). With the advent of integrated circuits in the 1960s, both ROM and its mutable counterpart static RAM were implemented as arrays of transistors in silicon chips; however, a ROM memory cell could be implemented using fewer transistors than an SRAM memory cell, since the latter needs a latch (comprising 5-20 transistors) to retain its contents, while a ROM cell might consist of the absence (logical 0) or presence (logical 1) of one transistor connecting a bit line to a word line.[12] Consequently, ROM could be implemented at a lower cost-per-bit than RAM for many years.

Most home computers of the 1980s stored a BASIC interpreter or operating system in ROM as other forms of non-volatile storage such as magnetic disk drives were too costly. For example, the Commodore 64 included 64 KB of RAM and 20 KB of ROM containing a BASIC interpreter and the KERNAL operating system. Later home or office computers such as the IBM PC XT often included magnetic disk drives, and larger amounts of RAM, allowing them to load their operating systems from disk into RAM, with only a minimal hardware initialization core and bootloader remaining in ROM (known as the BIOS in IBM-compatible computers). This arrangement allowed for a more complex and easily upgradeable operating system.

In modern PCs, "ROM" is used to store the basic bootstrapping firmware for the processor, as well as the various firmware needed to internally control self-contained devices such as graphic cards, hard disk drives, solid state drives, optical disc drives, TFT screens, etc., in the system. Today, many of these "read-only" memories – especially the BIOS/UEFI – are often replaced with EEPROM or Flash memory (see below), to permit in-place reprogramming should the need for a firmware upgrade arise. However, simple and mature sub-systems (such as the keyboard or some communication controllers in the integrated circuits on the main board, for example) may employ mask ROM or OTP (one-time programmable).

ROM and successor technologies such as flash are prevalent in embedded systems. These are in everything from industrial robots to home appliances and consumer electronics (MP3 players, set-top boxes, etc.) all of which are designed for specific functions, but are based on general-purpose microprocessors. With software usually tightly coupled to hardware, program changes are rarely needed in such devices (which typically lack hard disks for reasons of cost, size, or power consumption). As of 2008, most products use Flash rather than mask ROM, and many provide some means for connecting to a PC for firmware updates; for example, a digital audio player might be updated to support a new file format. Some hobbyists have taken advantage of this flexibility to reprogram consumer products for new purposes; for example, the iPodLinux and OpenWrt projects have enabled users to run full-featured Linux distributions on their MP3 players and wireless routers, respectively.

ROM is also useful for binary storage of cryptographic data, as it makes them difficult to replace, which may be desirable in order to enhance information security.

Since ROM (at least in hard-wired mask form) cannot be modified, it is only suitable for storing data which is not expected to need modification for the life of the device. To that end, ROM has been used in many computers to store look-up tables for the evaluation of mathematical and logical functions (for example, a floating-point unit might tabulate the sine function in order to facilitate faster computation). This was especially effective when CPUs were slow and ROM was cheap compared to RAM.

Notably, the display adapters of early personal computers stored tables of bitmapped font characters in ROM. This usually meant that the text display font could not be changed interactively. This was the case for both the CGA and MDA adapters available with the IBM PC XT.

The use of ROM to store such small amounts of data has disappeared almost completely in modern general-purpose computers. However, NAND Flash has taken over a new role as a medium for mass storage or secondary storage of files.

Mask ROM is a read-only memory whose contents are programmed by the integrated circuit manufacturer (rather than by the user). The desired memory contents are furnished by the customer to the device manufacturer. The desired data is converted into a custom mask layer for the final metallization of interconnections on the memory chip (hence the name).

Mask ROM can be made in several ways, all of which aim to change the electrical response of a transistor when it is addressed on a grid, such as:

Mask ROM transistors can be arranged in either NOR or NAND configurations and can achieve one of the smallest cell sizes possible as each bit is represented by only one transistor. NAND offers higher storage density than NOR. OR configurations are also possible, but compared to NOR it only connects transistors to Vcc instead of Vss.[13] Mask ROMs used to be the most inexpensive, and are the simplest semiconductor memory devices, with only one metal layer and one polysilicon layer, making it the type of semiconductor memory with the highest manufacturing yield[2] (the highest number of working devices per manufacturing run).

It is common practice to use rewritable non-volatile memory – such as UV-EPROM or EEPROM – for the development phase of a project, and to switch to mask ROM when the code has been finalized. For example, Atmel microcontrollers come in both EEPROM and mask ROM formats.

The main advantage of mask ROM is its cost. Per bit, mask ROM is more compact than any other kind of semiconductor memory. Since the cost of an integrated circuit strongly depends on its size, mask ROM is significantly cheaper than any other kind of semiconductor memory.

However, the one-time masking cost is high and there is a long turn-around time from design to product phase. Design errors are costly: if an error in the data or code is found, the mask ROM is useless and must be replaced in order to change the code or data.[14]

As of 2003[update], four companies produce most such mask ROM chips: Samsung Electronics, NEC Corporation, Oki Electric Industry, and Macronix.[15][needs update]

Some integrated circuits contain only mask ROM. Other integrated circuits contain mask ROM as well as a variety of other devices. In particular, many microprocessors have mask ROM to store their microcode. Some microcontrollers have mask ROM to store the bootloader or all of their firmware.

Classic mask-programmed ROM chips are integrated circuits that physically encode the data to be stored, and thus it is impossible to change their contents after fabrication.

It is also possible to write the contents of a Laser ROM by using a laser to alter the electrical properties of only some diodes on the ROM, or by using a laser to cut only some polysilicon links, instead of using a mask.[16][17][13]

By applying write protection, some types of reprogrammable ROMs may temporarily become read-only memory.

There are other types of non-volatile memory which are not based on solid-state IC technology, including:

Although the relative speed of RAM vs. ROM has varied over time, as of 2007[update] large RAM chips can be read faster than most ROMs. For this reason (and to allow uniform access), ROM content is sometimes copied to RAM or shadowed before its first use, and subsequently read from RAM.

For those types of ROM that can be electrically modified, writing speed has traditionally been much slower than reading speed, and it may need unusually high voltage, the movement of jumper plugs to apply write-enable signals, and special lock/unlock command codes. Modern NAND Flash achieves the highest write speeds of any rewritable ROM technology, with speeds as high as 10 GB/s. This has been enabled by the increased investment in both consumer and enterprise solid state drives and flash memory products for higher end mobile devices. On a technical level the gains have been achieved by increasing parallelism both in controller design and of storage, the use of large DRAM read/write caches and the implementation of memory cells which can store more than one bit (DLC, TLC and MLC). The latter approach is more failure prone but this has been largely mitigated by overprovisioning (the inclusion of spare capacity in a product which is visible only to the drive controller) and by increasingly sophisticated read/write algorithms in drive firmware.

Because they are written by forcing electrons through a layer of electrical insulation onto a floating transistor gate, rewriteable ROMs can withstand only a limited number of write and erase cycles before the insulation is permanently damaged. In the earliest EPROMs, this might occur after as few as 1,000 write cycles, while in modern Flash EEPROM the endurance may exceed 1,000,000. The limited endurance, as well as the higher cost per bit, means that Flash-based storage is unlikely to completely supplant magnetic disk drives in the near future.[citation needed]

The timespan over which a ROM remains accurately readable is not limited by write cycling. The data retention of EPROM, EAROM, EEPROM, and Flash may be time-limited by charge leaking from the floating gates of the memory cell transistors. Early generation EEPROM's, in the mid 1980's generally cited 5 or 6 year data retention. A review of EEPROM's offered in the year 2020 shows manufacturers citing 100 year data retention. Adverse environments will reduce the retention time (leakage is accelerated by high temperatures or radiation). Masked ROM and fuse/antifuse PROM do not suffer from this effect, as their data retention depends on physical rather than electrical permanence of the integrated circuit, although fuse re-growth was once a problem in some systems.[18]

The contents of ROM chips can be extracted with special hardware devices and relevant controlling software. This practice is common for, as a main example, reading the contents of older video game console cartridges. Another example is making backups of firmware/OS ROMs from older computers or other devices - for archival purposes, as in many cases, the original chips are PROMs and thus at risk of exceeding their usable data lifetime.

The resultant memory dump files are known as ROM images or abbreviated ROMs, and can be used to produce duplicate ROMs - for example to produce new cartridges or as digital files for playing in console emulators. The term ROM image originated when most console games were distributed on cartridges containing ROM chips, but achieved such widespread usage that it is still applied to images of newer games distributed on CD-ROMs or other optical media.

ROM images of commercial games, firmware, etc. usually contain copyrighted software. The unauthorized copying and distribution of copyrighted software is a violation of copyright laws in many jurisdictions, although duplication for backup purposes may be considered fair use depending on location. In any case, there is a thriving community engaged in the distribution and trading of such software and abandonware for preservation/sharing purposes.

However, RAM stores data temporarily while a device is running. Storage disks are similar to ROM in that they don’t lose their data after the device they’re installed in is turned off. Still, neither of those explanations answers the question, “What is ROM?” Luckily, this article will cover everything you need to know about this memory type, its subvariants, and how it all works.

If we want to define ROM, we should say it is a type of computer memory that can’t be modified by the user. It is used to store a device's BIOS (basic input/output system) and other important system files, i.e., a computer’s firmware. ROM is non-volatile, meaning it does not need power to retain its data.

Almost all computers contain a certain amount of ROM. It is used in video games, optical storage, compact discs (CD) such as a CD-ROM, as well as devices such as calculators or laser printers, and many others.

Many people confuse ROM and RAM and often talk about them interchangeably, but they have several key differences. For one, ROM is non-volatile, meaning it does not need power to retain its contents. RAM is volatile, meaning it requires power to keep its data stored. As soon as its home device is turned off, all data stored in the RAM is lost. Additionally, RAM has more extensive memory capabilities.

A small, long-lasting battery inside the computer powers the ROM, which comprises two main parts: the OR logic gates and the decoder. In ROM, input is received by the decoder in a binary form, while the output is its decimal equivalent. The decimal result of the decoder serves as the input for the OR gates in ROM.

There is a grid of columns and rows in ROM chips that can be turned on or off. If they are turned on, the value is 1, and the lines are linked by a diode. However, the lines are not connected if the value is 0. One storage element in the memory chip is represented by each element of the array.

The diodes allow a one-direction flow with a particular threshold called forward break over. This determines the amount of current needed before the diode passes the flow on. The forward break-over voltage is typically 0.6 V in silicon-based hardware.

ROM chips sometimes send a charge that goes above the forward break over to the column with a selected row that’s grounded to a particular cell. In cases when a diode is at the cell, the charge converts to the binary system, and the cell will be “on” at a value of 1.

1. PROM stands for programmable read-only memory. This type of ROM is a form of digital memory whose bits - basic units of data whose value can be either 1 or 0 - are locked by an anti-fuse or a fuse.A fuse begins with low resistance, and its job is to break the electrically conductive path when the current goes over a particular value. An anti-fuse works in the opposite direction  - it begins at high resistance and creates a conductive path in situations when the voltage goes over a specific value.

2. MROM is another type of read-only memory whose contents were programmed by the circuit manufacturer instead of the user. It got its name “masked read-only memory” because its chips are masked in the process of photolithography. When we talk about this type of ROM, we refer to a specific kind of ROM chip and not the entire memory category.

The current is sent from the ROM chip through input-output pathways. The locations of the fuses determine these pathways. The only way for the current to travel is through a fuse-enabled path, and the only way to go back is via the output chosen by the manufacturer. You cannot modify or rewire these ROM chips.

3. EPROM or erasable programmable read-only memory is sometimes referred to as ROM that can be reprogrammed. You’ll need to shine an intense UV light through a window inside the chip to perform erasure. Ordinary lighting is not strong enough for erasure, but bright sunlight could do the trick. In most cases, you’ll be able to perform about 1,000 erasures before the chips wear out.

4. EEPROM is another modifiable type of ROM. However, it’s much more convenient than others, as you can rewrite it without special equipment or removing it from the machine. If you want to make one edit, there’s no need to change everything.

ROM makes communication between hardware components possible. Also, it doesn’t need any refreshing due to its static nature. The ROM’s contents can always be verified, and it’s less expensive than RAM. Moreover, it’s more reliable than RAM because it’s non-volatile and way easier to test.

In fact, the read-only nature of this memory is simultaneously its biggest advantage and disadvantage. ROM memory can only display data and can’t be changed, which means that, if you want to overwrite, modify, or delete something, that won’t be possible. However, this also means your data won’t go missing, which turns it one of the most significant advantages of this type of memory.

There’s a variety of ROM applications in all sorts of electronic devices. The most common applications include:

It is hard to imagine what living in the 21st century would have looked like if computer gadgets weren’t in existence. From portable mobile phones to complex robotic machines used in manufacturing plants and industries, these computer gadgets contribute to make our lives easier in no small way.

Every electronic device depends on programs for their operations. These programs come in ones and zeros which is also known as machine language, and they are stored in the storage center of the computer.

The computer system comprises two major types of memory: the ROM and the RAM Memory. in case you are coming across ROM for the first time and you are wondering what the acronym could mean, ROM stands for Read-only memory. RAM stands for Random access memory and is called as such because the information stored in it is usually temporary in nature.

RAM memory is what most people are familiar with because it is removable and replaceable. Some typical examples of the RAM memory are the SSD cards used in a mobile phone and HDD cards that are commonly found inside computers and external hard drives.

So, what is the difference between a ROM chip and a RAM chip? ROM stands for “read-only memory” because any information that gets stored in this type of memory can only be read afterward, in other words, the information that is recorded into it cannot be rewritten all over again. This is why only important information that is repeatedly utilized by the computer or about it is usually stored in the ROM. Some of the important information includes the boot files and key program files. The first Semiconductor Diode Read-only memory chip was produced in 1965, and different types have been developed since then.

The information a ROM holds can both be referred to as permanent or semi-permanent (this is because a special operation may be required before the information stored in it can be modified). This is why it is possible for a computer system to go off and all the important information would still remain intact, unlike in a RAM where all operations done while a computer is going off will be immediately lost.

The ROM chip is therefore the most common memory chip because most electronic gadgets used for everyday activity perform repetitive tasks and do not require a constant change of programming aside from the one that has been built in by the manufacturer. The program files responsible for the operation are usually stored in a ROM Chip. A few examples of ROM chip-controlled devices that are used daily include printers, televisions, calculators, electric bells, game consoles, etc.

Now that you know the difference between the RAM and ROM and you can identify the several types that are available, you will now learn how to identify it anytime you come across one. To see a ROM, the computer device has to be dismantled as it is usually attached to the motherboard.

The process of dismantling a computer motherboard is quite different from computer to computer. For a desktop device, the board can be found after dismantling the CPU case while in a laptop, the motherboard will be found after dismantling the frame of the laptop. Once you have found the motherboard, you will be able to locate the ROM Chip by careful examination.

You must kindly note that there is no particular location on the board where the ROM must be found because this is subject to different variables such as the size of the board and a manufacturer may simply decide to place it anywhere they like. However, it is very common for manufacturers to install the ROM chip around the south bridge and peripheral card slots.

By close examination, the ROM chip can be identified by the text that is printed on it and the connection pins that attach it to the board. Most connection pins on ROM chips are often 28 or 30 in number, although there are a few instances where they are more than that. The manufacturer is at liberty to determine the number of pins they want to use. At the top of a ROM chip (which is often black in color), the manufacturer’s name is boldly written on it. Sometimes, the word BIOS is used instead of the manufacturer’s name with some coded numbers written beside it.

There are several small components like the ROM Chip that are products of several years of research and hard work. They are all put together to contribute to the overall working of these wonderful computer gadgets that make our living fun, interesting, and simple. Their operation seems magical, but the science behind their operation may sometime be very simple.

These beautiful gadgets that make our life so fun and easy are empowered to perform their respective tasks due to the information that has been programmed into them by their manufacturers. The programs are stored on the day the device was manufactured and will keep running until the device is no longer in use. The component where these important programs are stored for the entire lifespan of the device is what we have been discussing – the ROM chip.

The RAM and ROM are both important memory storage chips in a computer and they share a few similarities. However, they are different in terms of appearance, function, and operation. Below are the common differences between them, apart from the apparent difference that can be seen in the names:

* Any information that is stored in the ROM Chip comes directly from the manufacturer whereas; the RAM can be written and rewritten at any time by any user.

* Any information that is stored in a ROM Chip becomes permanently imprinted in it while the information that is stored on a RAM Chip is often temporary.

* The ROM is often referred to as a non-volatile memory because a sudden power outage doesn’t affect the information that is contained in it while the RAM is referred to as volatile memory because of the information stored in it can get lost once the computer system is turned off.

* The amount of information that can be stored in a ROM chip is usually smaller in size than the amount of information that a RAM can accommodate.

* The size of a computer RAM can be reduced or increased by replacing with another while the size of a ROM cannot be adjusted as it is only installed by the board manufacturer.

* The ROM chip plays the primary role in starting up a computer while RAM only becomes active when the computer is at work.

The importance of a ROM in the computer cannot be overemphasized as it is the most used storage. Due to recent advancements in computer engineering, several types of ROM have been developed for different purposes. There are currently four types of ROM: ROM chip, PROM chip, EPROM chip, and EEPROM chip.

This is the first type of Read-only memory chip to be developed, and most of what has been discussed earlier in this article are peculiar to it. As was discussed earlier, this type of memory can only support the writing of a file only once, and the file can only be read after that.

The downside of this memory is the cost involved in producing them in small quantities. This is because whoever is producing them has to program them from scratch, an activity that could be wasteful in case there is a problem with the program written into it. Furthermore, most manufacturers do not have the capacity to produce their own ROM and have to outsource the task to a third-party producer. Therefore, they cannot make modifications to whatever was produced for them.

Like any other technology, further research was carried out in order to develop better systems that are a modification to the ROM with the aim of addressing the downsides. This is the story behind the development of the other types of ROM that are given below.

PROM was developed in order to save the cost involved in ROM manufacturing. PROM is an acronym for Programmable read-only memory. As the name implies, the PROM Chip is a type of ROM chip that can be bought with nothing written on it by the producer and can be programmed by the computer manufacturer with the aid of a programmer.

This, therefore, eliminates the common issues that are associated with the ROM as the programmable read-only memory is much cheaper to produce than ROM. However, it is more fragile and less durable than ROM.

Therefore, PROM is more suitable for prototype testing where the manufacturer can test run the working of the computer system before requesting for mass production of the ROM from third-party producers. Similar to ROM, the PROM can only be programmed once and nothing else can be written on it nor modified once it is coded. This downside also led to further research that brought about the creation of other types of PROM.

The Erasable Programmable read-only memory, also known as EPROM, is an advanced type of PROM which was created to checkmate the drawback associated with the PROM. Since PROM can only be programmed once, an erasable variant of it was developed. Any file that is written on an EPROM can be erased and reprogrammed multiple times times. This is a great improvement from the ROM and PROM.

Erasing a program on an EPROM means that the entire program must be erased before a new one can be written in case an error was made during programming. This is a drawback because the EPROM doesn’t give a provision for partial erasures in situations where the correction that needs to be made is small. The act of erasing of an EPROM Chip is usually done with the help of a tool that uses ultraviolet light.

EEPROM is the fourth type of ROM, and the acronym stands for Electrically erasable programmable read-only memory. This type of ROM was created to eliminate the disadvantages associated with using EPROM that was discussed earlier. In EEPROM, a portion of a program can be erased electronically and replaced without affecting the other parts of the program.

Due to the way the EEPROM is designed to work, it is very slow in performance and therefore cannot be used in a computer system where the speed of operation is paramount. This is why a faster EEPROM was developed which is known as Flash memory.

This article is a very easy and descriptive guideline on a famous type of memory known as ROM (Read-Only Memory). ROM is one of the storage memories that can store the data permanently, this is why it lies in the category of non-volatile memory devices. Let’s find out more about ROMs.

Read-Only Memory is abbreviated as ROM. As it is obvious from the name, the contents of this type of memory can only be read but it is not true to some extent because there are types of ROM that can be re-written again and again. ROMs are non-volatile in nature meaning that the contents of these memories are not erased when the battery or power supply is disconnected.

All computers, laptops, and devices that have operating systems have an IC chip installed in their PCB (Printed Circuit Board) known as BIOS. BIOS stands for Basic Input/Output System. BIOS not only initializes the computer hardware but also it provides services to operating systems such as Windows and macOS etc.

All mobile phones have a ROM installed on them. These ROMs store the different functionalities of your cell phone. For example, the keypads in the cell phones use ROM for dialing numbers and codes while in the smartphones the ROMs control the touch screen drivers. ROMs are also used for storing the operating systems and built-in apps and services in mobile phones that’s why even after the factory reset you can find these apps on your phone.

ROMs are not only used as firmware but also as a tool to update the firmware. Firmware are program codes written on the ROMs permanently for performing some functionalities throughout the life of a device. These are present in the webcams, printers and scanners, digital televisions, USB flash drives, etc.

Microcontrollers or MCU are programmable intelligent circuits that have a small processor on them. MCU (Microcontroller Units) have ROMs embedded on their PCBs (Printed Circuit Board) for storing the program instructions. All types of Arduino, Atmega328p, AVR, PIC, and 8051 are examples of Microcontrollers.

VCRs (Video Cassette Recorders), CD and DVD Drives, Digital Cameras, Digital Watches, Computer Modems, Graphic Cards, Computer Processors, LCD and LED Monitors, etc have ROMs installed on them. Nearly all digital devices have ROMs for performing various built-in and iterative operations.

Nowadays, digital electronic instruments are used instead of old analog meters with needles. These instruments not only give us error-free results but they also provide us readings with more precision and accuracy. This is all possible due to the ROMs installed in these scientific instruments.

ROM is a type of memory that is programmed only once and whose contents can only be read again and again by a device or a user. Most of the ROMs are not updatable and most don’t even allow you to copy their contents. This prominent property of ROMs makes them Read-Only Memories.

ROMs are non-volatile meaning you can disconnect the device with ROM installed in it from a power source or battery and the ROM will still retain its belongings without any problems. Because of this feature ROMs are used in almost every kind of digital device as we shut down or disconnect most of the devices when we don’t intend to use them.

If memory is easily programmable, you can program it according to your project or product needs. Thankfully, ROM is a programmable memory chip. You can purchase a ROM from the market and program it according to your project needs but make sure that it allows you to modify your code multiple times. There are a variety of programmable circuit boards available in the shops as well that contain ROMs.

Dawon Kahng and Simon Sze discovered ROM (Read-Only Memory) in 1967 at Bell Labs. These genius engineers belonged to Korea and China respectively. They proposed that FGMOS transistors can be used as a memory that will have the capabilities of getting reprogrammed and now there is hardly a digital device on this earth that does not have a ROM installed in it.

There are two essential components of ROM, OR logic gates and Decoder. Decoders are responsible for converting high-level code into low-level binary language and vice versa. The OR gates receive the inputs from the decoder and perform the functions accordingly. The logic gates in a ROM are used in a manner that they can permanently store the instruction code or data.

By providing the address as an input to a ROM it gives out the data and instructions stored in it. This happens frequently when a user uses a digital device.

MROM is an abbreviation of Masked Read-Only Memory. Mask is a photograph of the template of the circuit that engineers want to make a ROM of. This circuit has all the functionalities that will become the built-in functions of a ROM. But this template must be provided to the manufacturers of MROMs.

MROMs were old technology and only manufacturers could build and program them in bulk quantities. The method of writing the contents into a Masked ROM is known as Mask Programming. The contents of MROM cannot be changed and are written permanently on them.

Due to these limitations, MROMs could not become famous as the scientists and programmers want something they can program and modify by themselves.

PROM means Programmable Read-Only Memory. This memory was made for the programmers so they can write their own code without having to go to a manufacturer and pay high prices. There is a special device that is used to write data into PROM called PROM Programmer. Writing code using this device is a very difficult and burdensome process.

The program written in a PROM can never be changed afterward. Hence, an error that is causing the ROM not to work correctly cannot be removed. As a result, the ROM becomes completely useless.

A genius from Intel, Dov Frohman, invented Erasable Programmable Read-Only Memory (EPROM) in 1971. This memory was created to overcome the limitation of PROM. The contents of a PROM could not be erased but the code and data of an EPROM can be easily erased. This allows a programmer to reprogram the chip instead of throwing it into a recycle bin.

As we described, EPROM can be reprogrammed after putting it in a device called EPROM Eraser. This eraser has UV light compartments in it and exposure to Ultraviolet Light erases the data of an EPROM. Because of this feature, the EPROMs are used for making projects that need modifications during development.

The contents of an Electrically Erasable Programmable ROM can be erased electrically using a signal. This is why this is the most popular type of ROM. This property allows the programmers to modify the code multiple times without having to wait for UV light to erase the contents.

In most cases, there is no need to remove the EEPROM from the socket when reprogramming it. Because of these features, EEPROMs are used in most of the latest digital devices whose software can be updated and reinstalled in case of getting corrupted. The devices with EEPROM have a greater life span.

Flash is a very fast memory that is used in the latest devices. The basic component of Flash Memory is FGMOS (Floating Gate Metal-Oxide-Semiconductor Field-Effect Transistor). The ROM made up of Flash Memory is known as Flash ROM. It is used in industrial applications and consumer devices such as computers, mobile phones, digital televisions, etc.

ROM stands for Read-only Memory and it is a non-volatile memory present in the form of programmable IC chips. ROM is used as firmware in digital electronic devices for providing built-in functionalities such as computers, laptops, mobile phones, digital televisions, etc. Read-Only Memory not only initializes the hardware but also loads the operating system in the RAM.

RAM stands for Random-Access Memory and it is used in fewer devices than ROM. RAM is a volatile memory meaning it cannot retain its contents when the power is disconnected. RAM is the only way to communicate with processors. Running apps and data being processed resides in the RAM. It also gives space to the processing results. Learn more about what is RAM.

This article is a very simple and easy guideline on ROM (Read-Only Memory). By reading this article, you will learn about the basics of ROM and the category in which this memory lies. Along with the working of ROM, you are also guided on the different types of ROM such as MROM, PROM, EPROM, EEPROM, etc.

ROM (read-only memory) is a non-volatile memory type. This means it receives data and permanently writes it on a chip, and it lasts even after you turn off your computer. The data is coded to not be overwritten, so it's used for things like your printer software or your startup programs.