By : Reem Hasayen

A storage device is a hardware device capable of storing information. There are two types of storage devices used in computers 1. Primary storage device such as RAM and Cache 2. Secondary storage device such as a computer hard disk drive

 Also known as internal memory and main memory.  primary storage is a storage location that holds memory for short periods of times while the computer is on. For example, computer RAM and Cache.

 RAM 1. Smaller amount (typically 128MB-1 GB) 2. Temporary storage of files and programs. 3. Contents disappear when you turn off power to the computer. 4. Consists of chips ( microprocessors)  Hard Drive 1. Much larger amount (typically 1 GB- 400 GB ) 2. Permanent storage of files and programs. 3. Contents remain when you turn off power to the computer. 4. Consists of hard disks ( platters)

 RAM 5. Contents are stored electronically in bits on the chips, in electronic offs and ones (0’s and 1’s), so RAM needs electrical power to hold information.  Hard Drive 5. Contents are stored magnetically, also in bits which are offs and ones or (0’s,1’s),so the hard drive does not need power to hold information.

 This type of memory has 4 fundamental features: 1. Speed. 2. Capacity. 3. Volatility. 4. Random.

 Information in RAM is stored based on electrical signals….so to change information simply requires sending different electrical signal to the chip. This happened very fast.  Using the hard drive need to move a physical object “ head” that is spinning to the right position, this is very slow

 This mean that data loaded into RAM is only stored temporarily until the PC is turned off

 Advantages : Fast  Disadvantages: 1. “Forgets” when you turn the computer off. 2. more expensive than the hard drive storage.

 This memory is an ultra fast memory that allow the CPU to perform certain operation in very brief period of time.  It takes information from RAM memory and send it directly to the CPU to be executed.

 The hard drive also called “Storage” or “ Disk Space” and its measured by (MB) or (GB)  Hard drive consist of a metal platter which spin very fast.  As it spins the hard drive head moves along the platter and can read and write information.

 Advantages: 1. relatively cheap. 2. can turn off the computer and reload the information later  Disadvantages: since it’s a mechanical device( spinning platter) it can be slow.

 Spindle Rotation Speed  Seek Time

 On each of the platters there is a thin layer of magnetic film.  Data storage on hard disks is very similar to that of a cassette tape.  Data is stored in many 1's and 0's. These binary digits are arranged in different ways to represent different characters.

 DNpQ