2.2.4.1 Explain types and functions Primary & Secondary Storage

Primary Storage (RAM, ROM)

Primary storage is the main memory in a computer. It stores data and programs that can be accessed directly by the processor. There are two types of primary storage which are RAM (Random-Access Memory) and ROM (Read-Only Memory). RAM is installed inside computers. RAM is also known as a working memory.

RAM:

• The data in RAM can be read (retrieved) or written (stored).

• RAM is volatile (the programs & data in RAM are lost when the computer is powered off).

• Computer uses RAM to hold temporary instructions and data needed to complete tasks. This enables CPU to access instructions and data stored in the memory very quickly.

• RAM stores data during and after processing.

ROM:

• ROM is another type of memory permanently stored inside the computer.

• ROM is non-volatile (holds the programs and data when the computer is powered off).

• Programs in ROM have been pre-recorded by the manufacturer. Once it is done, it cannot be changed.

• Many complex functions, such as start up operating instructions, translators for high-level languages & operating systems are placed in ROM memory.

• All the contents in ROM can be accessed and read but cannot be changed.

Secondary Storage
Secondary storage can be divided into magnetic medium, optical medium and flash memory.
Magnetic Medium
Magnetic medium is a non-volatile. It can be any type of storage medium that utilizes magnetic patterns to represent information. The devices use disks that are coated with magnetically sensitive material. The examples of magnetic storage are:
• magnetic disk such as:
- a floppy disk, used for off-line storage
- hard disk, used for secondary storage
• magnetic tape;
- including video cassette, audio storage reel-to-reel tape & others.
Optical Medium
Optical medium is a non-volatile storage that holds content in digital form that are written and read by a laser. These media include various types of CDs and DVDs.
These following forms are often commonly used :
• CD, CD-ROM, and DVD: Read only storage, used for distribution of digital information such as music, video and computer programs.
• CD-R: Write once storage, the data cannot be erased or written over once it is saved.
• CD-RW, DVD-RW, and DVD-RAM: Slow to write but fast reading storage; it allows data that have been saved to be erased and rewritten.
The disk capacity of optical media is more compared to magnetic media. Durability is another feature of optical media, they are able to last for up to seven times as long as traditional storage media.
Flash Memory
Flash Memory is a solid-state, non-volatile, rewritable memory that functions like RAM and a hard disk drive combined. Flash memory store bits of electronic data in memory cells just like DRAM (Dynamic RAM), It also works like a hard disk drive that when the power is turned off, the data remains in the memory. Flash memory cards and flash memory sticks are examples of flash memory.
Flash memory cards are also used with digital cellular phones, MP3 players, digital video cameras and other portable digital devices.
Flash memory is also called USB drives, thumb drives, pen drives or flash drives, are the up-and-coming players in the portable storage market.
The advantages of flash memory are, it offers fast reading access times (though not as fast as RAM) it is durable and requires low voltage. It is also light and small. The disadvantage is, it is more expensive than the magnetic disk of the same capacity.