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Computer Storage & Memory

Computer Memory and Storage Explained

What is computer memory and data storage?

Computer memory and storage are two internal components of modern computers. They’re responsible for one of the most essential and primary functions in a computer: storing data in digital formats. Advances in computer memory and storage represent some of the most significant breakthroughs in computing over the last 50 years.

What are the differences between memory and storage?

The terms memory and storage are sometimes confused and thus used interchangeably, but they are different components in a computer that serve different functions. Memory, or primary storage, is the component that is directly accessible by the Central Processing Unit (CPU), which is the main “brain” that carries out commands in a computer. The function of memory is to temporarily hold onto certain pieces of data that the CPU is actively using. Whenever a person is using a computer program or looking at a file, that data is contained in the memory for the CPU to access. The CPU accesses the memory by way of a component called a memory bus. In most cases, memory is volatile: when the computer is shut down, whatever data that was stored there is lost. The exception to that is BIOS, which are basic commands the computer uses every time it boots up. That memory is non-volatile and isn’t erased when the computer is shut down. Primary storage is the smaller of the two components in terms of overall storage size.

Data storage, or secondary storage, is a component that is not directly accessible by the CPU. It holds onto data that the CPU is not actively using. When the CPU needs data that is stored on secondary storage, the data must first be transferred to the memory by what are called input/output (I/O) channels. Secondary storage is non-volatile. Secondary storage is stored internally in computers usually in the form of a hard drive: a device that contains spinning platters onto which information is “written” magnetically. There are also external hard drives which can be connected to the computer by cables, as well as USB flash drives which plug directly into a computer’s USB port. Secondary storage is the larger of the two components in terms of overall storage size. Many modern hard drives permit operating systems to use some of the hard drive’s space as if it were memory, a concept called “virtual memory.” This is useful when all of the available memory has been used and CPU needs to access even more data.

The capacities of both memory and hard drives are expressed in bytes. Computers store data using a binary system: information is converted into a string of numbers that either have a value of 0 or 1. Each number is called a bit; eight bits make up a byte. The following chart illustrates the relative size of larger amounts of data:

8 bits = 1 byte

1000 bytes = 1 kilobyte (KB)

1000 kilobytes = 1 megabyte (MB)

1000 Megabytes = 1 Gigabyte (GB)

1000 Gigabytes = 1 Terabyte (TB)

1000 Terabytes = 1 Petabyte (PB)

The history of computer memory

Before the invention of the modern semiconductor, computer memory was stored using different methods, such as punch cards or tape and magnetic drums or cores. Memory as we understand it today (RAM) was invented by the Intel Corporation in 1969. Early chips held about 2 KB of memory, much less than the file size of a normal email. The storage capacity of memory grew steadily over the next few decades. By the mid-1990’s, when Windows operating systems became the leader in PC market share, computer memory was anywhere from 16 to 64 MB, depending on the particular brand and model of the computer. Today, however, even the cheapest of commercially sold computers will have several gigabytes of RAM. As you can see, there has been an exponential leap in the memory capacities of computers.

The history of data storage

Just as memory capacities have grown by leaps and bounds over the last few decades, so have hard drives and other secondary storage options. The earliest computers lacked a true internal hard drive. All non-temporary data had to be stored on external tapes or disks, a technology which continued in use even as internal hard drives became more and more common. IBM in the 1950’s created internal hard drives that stored 4 to 10 MB of data, but on devices that we would not consider personal computers today. Even into the early 1980’s many personal computers lacked an internal hard drive. It wasn’t until the late 1980’s and early 1990’s that hard drives became standard features in personal computers. They could hold a few hundred megabytes. By 1995, gigabyte size hard drives in personal computers were available and by 2000 that number had grown to 10 gigabytes or more. Today you can purchase a hard drive measured in terabytes.

Types of computer memory

Computer memory today is referred to as RAM: Random Access Memory. There are two main types of RAM: Static and Dynamic. Static RAM (SRAM) does not have to be “refreshed” with continuous surges of electricity to hold onto the data. As long as the computer remains on, the data remains there. Dynamic RAM (DRAM), however, has to be refreshed thousands of times per second or it loses its data. In terms of speed, SRAM is superior, but it also requires more transistors and capacitors per bit, making it bulkier and more expensive. As a result, DRAM is the most common type of RAM found in personal computers. It comes in three main types today:

  • Synchronous DRAM (SDRAM): This type of DRAM synchronizes with the internal clock that is found on the CPU. Because it’s “in time” with the CPU, it runs at much higher speeds than earlier forms of DRAM.
  • Rambus DRAM (RDRAM): A proprietary type of SDRAM licensed by the Rambus Corporation that uses double data rate transfer. All CPU’s have an internal clock that is synchronized by the rising and falling of a signal wave. In double data rate transfer, information is moved around at both the top and bottom of the clock signal. This in effect doubles the speed at which the CPU can access information from the DRAM.
  • Double Data Rate SDRAM (DDR SDRAM): a class of non-proprietary SDRAM that also utilizes double data rate transfer. It largely won out against RDRAM because it was cheaper and the RDRAM did not offer superior enough performance rates. This is the most common RAM used today, already in its fourth generation of production (DDR4 SDRAM).

Types of data storage

The main types of secondary storage are internal hard drives, external hard drives, USB flash drives, CD/DVD drives, and cloud storage.

  • Internal hard drives today come in up to 3 terabyte sizes. They can be installed directly into the housing of a computer. They range in price from $50 to $250.
  • External hard drives are sold individually or grouped together in what are called arrays. Individually, they are similar in size to internal hard drives. In array form, they can hold up to 10 terabytes of data. They range in price from $50 (for single drives) to $1500 (for a high-end array).
  • USB flash drives, also known as thumb drives due to their size, connect into a computer’s universal serial bus (USB) port. These drives have no moving parts and draw their power directly from the computer itself. They come in sizes up to 256 gigabytes.
  • CD and DVD drives are optical drives that use laser technology to read and write data onto compact discs and digital video discs. While most computers still incorporate these drives, they are more used for media consumption than storage. Individual CD’s and DVD’s do not hold enough data compared to other data storage options.
  • Cloud storage is the storing of data online by external third-party servers. This model of data storage is becoming increasingly popular for a few reasons. One, cloud storage, in practice, offers unlimited storage capacity. Two, the data can be accessed anywhere from the world with an internet connected computer, not just locally. Three, the data is stored on multiple, redundant servers, so it’s nearly impossible to have the data lost or erased. If one server is down, the data can be accessed from one of the other servers it’s hosted on.


Upgrading computer memory

Because there are many different types of memory, always check which particular type your computer uses before upgrading. In some cases, there is an empty slot for you to simply add another memory chip to your existing memory. In other cases, you need to swap out the old memory for a new memory chip. Memory chips also have a specific number of little metal pins that secure the memory chip in place. If the number of pins in a chip does not match the number of pin holes in the computer, it will not work. Whenever you are in doubt, consult a professional. Simply by telling them the make and model of your computer they should be able to tell you what your memory needs are. If all else fails, simply bring in the computer itself.

If improving the speed or performance of your computer is your goal, the best bang for your buck is memory. Increasing the secondary storage will not improve speed. A useful analogy to think of is pools and pipes. A hard drive is like a pool of data: it holds a lot of it. Memory, however, is like a pipe: it also holds data, but less of it. But the bigger the pipe, the more data that can flow through it to the CPU, just like water in a pipe. Increasing your memory will allow more data to flow to the CPU at any given moment, regardless of the hard drive capacity.

Upgrading data storage

If speed is not an issue, but permanent file storage is, consider upgrading your secondary storage capacity. Internal drives need to be compatible with the motherboard of your computer and have to be installed manually, so check with a professional before upgrading. External drives and USB flash drives use cables or plug directly into a computer, so there is no need to check for compatibility, nor installation. They will be ready to work out of the box. If you are considering cloud storage, you will need to find a provider of cloud services. Conduct some research online and comparison shop. Since servers work all over the world, there is no need to purchase services from a local company.