1.1 Secondary memory or storage

Secondary Memory is used to store information that must later be transferred to the main memory.

It's the place where all of the programs are kept when they are not in use.

Secondary Storage is on media external to the computer and commonly consists of hard disk, or CD-ROMs.

Each Secondary Memory device has unique features and satisfies certain computer storage needs.

1) speed and access time;

2) Cost/removable versus non-removable;

3) Capacity;

4) Type of access;

*The speed of a device is sometimes referred to as its Access Time; the access time of a storage device is either (read time) or (write time).

*Cost is another way to characterize secondary storage devices.

In many secondary storage devices the actual place where the binary information is stored is removable.

The first part is the cost of the actual medium used to store the bits.

The second cost is the price of the drive unit that accesses data on the medium.

*The capacity: the hard drive capacities range from hundreds of megabytes to several gigabytes.

*Type of access: there are two types of access:

1) Random Access: To storage allows information to be obtained directly rather than by sifting through other information to reach it. example (Hard Disk).

2)Sequential Access: Storage allows the desired information to be obtained by starting at the beginning of a list of information and the proceeding item by item until it is reached. example (Magnetic tape)

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