Difference between Primary Memory and Secondary Memory

Primary Memory: Primary memory holds the programs and data required by the CPU for carrying out its operations.
Types of Primary Memory:
A. Random – Access Memory (RAM): RAM has become the synonym for main memory. RAM is very fast, the access time is in Nano seconds. RAM is volatile that is the contents of RAM are lost when the power supply to the RAM is discontinued. RAM is further divided into two types of memories-
a. Dynamic Random Access Memory (DRAM): In this type of memory the data is stored in cell of transistors and capacitors and the data has to be refreshed every few milliseconds.
b. Static Random Access Memory (SRAM): This does not require periodical refresh. SRAM is faster than DRAM but it is more expensive as compared to DRAM.
B. Read Only Memory (ROM): A part of computer storage is ROM that cannot be erased or changed. ROM is nonvolatile i.e. its contents are not lost when power is switched off. ROM is also divided into two types of memory:
a. Programmed Read Only Memory (PROM): This is used for storing some specialized application by the computer designers instead of chip designers. PROM can be written only once.
b. Erasable Programmed Read Only Memory (EPROM): This can be erased and programmed many times.
Secondary Memory: The secondary memory is non-volatile and has larger capacity. The most common form of secondary storage devices are magnetic tapes and magnetic disks.