Memory and storage

All computers require storage space and memory to run programs and store files. There are different types of memory and storage, and each has its own purpose. Most people use a combination of the following storage devices.

Hard disk drives

Every computer has one or more disk drives—devices that store information on metal or plastic disks. Hard disks can store a vast amount of information, including photos, videos, music, documents, programs and more. Your computer's hard disk drive stores information even when your computer is turned off. For more information about hard disk drives, see Parts of a computer and Install or remove a hard disk drive.

Picture of a hard disk drive
Hard disk drive


Random access memory (RAM) is temporary storage space that your computer uses to run Windows and other programs. RAM isn’t used for storage when your computer is turned off. It’s different from disk space, which is the amount of storage space available on your computer's hard disk.

Different computers and programs have different RAM requirements. To learn more about RAM, see What is virtual memory? and Find out how much RAM your computer has. To learn how to install more RAM, check the information that came with your computer or go to the manufacturer's website.

External hard disks

The simplest way to add more hard disk space to your PC is to plug in an external hard disk. An external hard disk is a great way to store more digital photos, videos, music, and other large files. It can supplement the storage space on your computer’s internal hard disk, especially if your internal hard disk is running low on space. An external hard disk is also a great way to store a backup copy of important files.

To install an external hard disk, plug it into your computer and connect the power cord. Most of these hard disks plug into a USB port. Note that you might need to install software that came with the hard disk. To do this, follow the instructions from the manufacturer. You can read more about external hard disks at What is Enhanced Storage? and Install or remove a hard disk drive.

USB flash drives

A USB (universal serial bus) flash drive is a small, portable device that plugs into a computer's USB port. Like a hard disk, a USB flash drive stores information, but usually a lot less than most hard drives. USB flash drives vary in size and shape and can hold gigabytes of information. They’re sometimes called thumb drives because they’re about the size and shape of a person’s thumb. They can be carried around easily, which makes them a good choice for transferring information from one computer to another. USB flash drives are also called pen drives, key chain drives, key drives, or memory sticks.

Illustration of a USB flash drive
USB flash drive

CD and DVD drives

Nearly all computers today include a CD or DVD drive, usually located on the front of the system unit. CD drives use lasers to read (retrieve) data from a CD; many CD drives can also write (record) data onto CDs. If you have a recordable disk drive, you can store copies of your files on blank CDs. You can also use a CD drive to play music CDs on your computer.

DVD drives can do everything that CD drives can, plus read DVDs. If you have a DVD drive, you can watch movies on your computer or play music CDs. Many DVD drives can record data onto blank DVDs.

Memory cards

Flash memory cards store computer information such as text, pictures, and music. You can erase and reuse memory cards over and over. Most digital cameras store pictures and video on a CompactFlash memory card or a Secure Digital (SD) card.

Illustration of flash memory cards
Memory cards

You can use a USB cable to move pictures from your camera to your computer, or you can use a memory card reader.

Illustration of a memory card reader
Memory card reader

When you insert your memory card into a compatible card reader attached to your computer, you can copy your pictures from the memory card to your computer without draining your camera’s battery, dealing with connection cables, or installing additional software. Some computers and laptops have a built-in memory card reader. Other card readers plug into a USB port on a computer. For more information, see How do I get pictures from my camera to my computer? and Working with digital pictures.

Backing up your files

Always be sure to save a copy of your important files to a second location, no matter what method you use for the original storage. Then, if your hard disk ever fails, you won't lose your data. You can use an external disk drive, CD or DVD disk, USB flash drive, or another storage device to back up your files. For more information about backing up files, see Where should I save my backup?