1. Computer Memory/Storage Device
Process of storing information in computer is called storage. The devices used to store data are called storage devices.
Types of storage device.
Primary storage devices (Also Internal Memory )
Secondary storage devices ( Also External Memory )

2. INTERNAL MEMORY /PRIMARY MEMORY
Storage devices which are installed at the mother board are called primary storage device. It is called also memory.
ROM
Read Only Memory (ROM) is "built-in" computer memory containing data that normally can only be read, not written to The ROM is non-volatile memory; it retains stored information even if the power is turned off. There are some more types of ROM such as (PROM , EPROM, EEPROM) .

3. INTERNAL MEMORY /PRIMARY MEMORY
RAM
Random Access Memory (RAM) The physical memory that is installed in a computer system is referred to as random access memory. RAM is volatile, which means it needs power from the computer in order to store data. Once the system is turned off the data is lost. Here we can read , write and modify of data.

4. External Memory/ Secondary StorageDevice
1) Magnetic Tap. 2) Magnetic Disk 3) Optical Disk
External memory is a type of data storage device for a computer that is kept outside of the computer in its own casing. The hard disks, floppy disk, USB flash disk, optical disk (CD/DVD) Compact disk and digital versatile disc are example of external storage device