SECONDARY MEMORY.docx

**SECONDARY MEMORY** This is the permanent, non-volatile memory that is not directly accessed by the computer/processor. Before the content of the secondary memory can be used by the computer, it must be copied into the RAM. It has the capacity to store huge amount of data. The secondary storage is...

**SECONDARY MEMORY** This is the permanent, non-volatile memory that is not directly accessed by the computer/processor. Before the content of the secondary memory can be used by the computer, it must be copied into the RAM. It has the capacity to store huge amount of data. The secondary storage is the slowest and cheapest form of memory. Examples of secondary storage include Hard Disk (Local Disk), Optical disk (CD, DVD), Floppy Disk, USB flash drive, memory card etc. **Differences between primary and secondary memory** **Primary** **Secondary** ---------------------------------------------- ------------------------------------------------- It is the internal memory It is the external memory It is under the direct control of the CPU It is not directly under the control of the CPU It cannot be used for massive data storage It can be used for massive data storage It is faster than the secondary storage It is slower than the primary storage It does not supplement the secondary storage It supplements the primary storage **Unit of storage** The storage capacity is the amount of space available for the storage of data in a particular storage media. The storage unit includes: ·         Bits: a bit is a contraction of the word "binary digit" and is denoted with either 1 or 0. A bit is the simplest unit of data storage. ·         Nibble: a nibble is a collection of 4 bits ·         Byte: a byte is a collection of 8 bits ·         Word: a word is 2 bytes ·         Kilobyte: a kilobyte is 1024 bytes (1000 bytes approximately) ·         Megabyte: a megabyte is 1048576 bytes i.e. 1024^2^bytes (1 million bytes approximately) ·         Gigabyte: a gigabyte is 1073741824bytes i.e. 1024^3^bytes (1 billion bytes approximately) ·         Terabyte: a terabyte is 1099511627776 bytes i.e. 1024^4^bytes (1 trillion bytes approximately) **Conversion from one unit of storage to another** 1.      Convert 64 bits to byte Solution:          8 bits make 1 byte                                     1 bit makes 1/8 byte 64 bits make 1/8 x 64 = 8 bytes 2.      Convert 16384 bits to byte and kilobyte Solution:          **a**. 8 bits = 1 byte                         1 bit     = 1/8 byte                         16384 bits = 1/8 x 16384                                     = 2048 bytes                         **b.** 1024 bytes = 1 KB                         1 byte = 1/1024 KB                         2048 bytes = 1/1024 x 2048                                     = 2KB