A Bit About Memory – ROM & RAM

The differences between volatile and non-volatile memory.

As I mentioned in a previous post about the various components of a computer system, computer memory provides a temporary workspace for the CPU to be able to carry out the various tasks required of it.

Following on from that brief introduction, it’s worth taking a look at memory in more detail, specifically the two different types and what they are able to offer the computer system.

Volatile versus Non-Volatile Memory
Before we get right down to the specifics of the types of memory used within a computer system, it’s important to note that computer memory is broadly considered to be either volatile or non-volatile.

As the names might suggest, one of these memory types is much more unstable than the other and requires some form of input to keep it.  In this case, volatile memory requires a power source in order for the information contained on it to be kept.  If the power source is removed, then the memory is ‘wiped’ and the information lost.

Alternatively, Non-volatile memory is able to retain the information contained on it, regardless of whether or not there is a power supply present.

The two different types of such memory used within a computer system are Random Access Memory (RAM) and Read Only Memory (ROM).  These alternative types of memory, unsurprisingly, work differently and are utilised in different ways by the CPU.

Random Access Memory (RAM) is a method of storing information and acts as the computers main ‘short term memory’ or ‘workspace’ as I previously described it.  RAM needs a constant power supply in order to retain and access the information it contains and if the power supply to RAM is lost, then the information contained within it will also be lost.

The CPU is able to access any piece (or byte) of information stored in the RAM without disrupting any other information also stored there.  Likewise, the CPU is also able to write to the RAM without deleting any other information that is still needed by any running processes.

Note:  When a computer process is stopped (e.g. closing a program), the associated information within the RAM is then disposable and can be written over by the CPU.

Read Only Memory (ROM) is a form of non-volatile memory that retains it’s information regardless of whether there is a power supply present to it or not.  Information contained in ROM is easily readable by the CPU but is very difficult for the system to modify.

At this point, you might be wondering why such types of memory have any relevance in a computer system and why unchangeable information is of any use.  It’s actually fundamental to the operation of a computer system and, without it, your computer would be little more use than a paper weight.

ROM contains such information as required by the CPU to initiate and run at start up. Data stored on ROM informs the CPU of the parameters to initiate within the start up sequence and enable the computer to run prior to the Operating System (OS) starting up.



  • Is a form of volatile memory and only retains it’s information while power is present
  • Is easily accessible for reading from AND writing to by the CPU
  • can be read from or written to without disturbing any other information stored on it
  • contains information that is considered to be temporary by the computer system
  • Is a form of non-volatile memory and retains it’s information regardless of whether power is present.
  • Is easily accessible for reading from by the CPU
  • can be read from without disturbing information contained on it but cannot be written to very easily.
  • contains information that is not considered temporary by the computer system
Study Reference Disclaimer. 

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