The Differences Between RAM, ROM & Secondary Memory

Many times, people seem to find it difficult to differentiate between ROM and secondary memory. In this regard, I've prepared this article to make clarity on what a ROM is and what a secondary memory is.

RAM:

As we all know, RAM stands for "Random Access Memory". It's the primary kind of memory that a computer needs to function. It temporarily stores data, which are basically the operating system, application system and programs that are in use and so is usually small in size. Data on the RAM can be accessed only when the system is on. Once you power off your computer, the data on the RAM is wiped off.

On phones, the common sizes of RAM range from 512Mb to 3Gb, although some smartphones can have up to 6Gb of RAM.  While on PCs, you can have RAMs ranging from 2Gb to 4Gb (being the common ones) but some PCs have upto 8Gb of RAM.

Task manager showing RAM space used by apps currently in use 

ROM:

Read Only Memory (ROM), as the name implies, can only be read. The user can't edit data on the ROM neither can he remove or add data. The ROM stores manufacturers information and other details of the device (or PC) and also stores vital information required for booting the system. All these data/information can only be read and cannot be manipulated. The ROM is usually smaller in size compared to the RAM. A ROM chip stores several megabytes (MB) of data, typically 4 MB or 8 MB per chip.

Note that when I say "size" in this context, I mean data storage size and not physical size.

Secondary Memory:

The secondary memory is a term used to describe a digital storage device that can store data permanently. They usually have larger storage capacities and have the capabilities to store data permanently. They include hard drives, flash drives, floppy disks, CDs, memory cards e.t.c. As stated, they have larger storage capacities ranging from 2Gb to 2Tb (being the common ones). Some secondary storage devices have higher storage capacities.

It should also be noted that the RAM & ROM are internal memories (only found inside the computer system) whereas we have internal and external secondary memory/storage devices.