COAL Lesson 3

Memory

is used for the information in physical systems which are fast (i.e. RAM).

Computer Memory

a physical device that is used to store data, information and program in a computer.

Types of Computer Memory

Primary memory; Secondary memory

Primary memory

includes ROM and RAM, and is located close to the CPU on the computer motherboard, enabling the CPU to read data from primary memory very quickly indeed. It is used to store data that the CPU needs imminently so that it does not have to wait for it to be delivered.

Primary Memory Types

RAM, or random access memory; ROM, or read-only memory

RAM

random access memory

ROM

read-only memory

RAM Computer Memory

_______ memory is very fast, it can be written to as well as read, it is volatile (so all data stored in______ memory is lost when it loses power) and, finally, it is very expensive compared to all types of secondary memory in terms of cost per gigabyte

DRAM

it is the most common type of RAM used in computers. The oldest type is known as single data rate (SDR) DRAM, but newer computers use faster dual data rate (DDR) DRAM.

SDR

single data rate

DDR

dual data rate

SRAM

particular type of RAM which is faster than DRAM, but more expensive and bulker, having six transistors in each cell.

PROM

stands for Programmable Read-Only Memory, and it is different from true ROM in that while a ROM is programmed (i.e. has data written to it) during the manufacturing process,.

EPROM

stands for Erasable Programmable Read-Only Memory, and as the name suggests, data stored in an EPROM can be erased and the EPROM reprogrammed. Erasing an EPROM involves removing it from the computer and exposing it to ultraviolet light before re-burning it.

EEPROM

stands for Electrically Erasable Programmable Read-Only Memory, and the distinction between EPROM and EEPROM is that the latter can be erased and written to by the computer system it is installed in. In that sense EEPROM is not strictly read-only. However in many cases the write process is slow, so it is normally only done to update program code such as firmware or BIOS code on an occasional basis

Secondary memory

is usually physically located within a separate storage device, such as a hard disk drive or solid state drive (SSD), which is connected to the computer system either directly or over a network. The cost per gigabyte of secondary memory is much lower, but the read and write speeds are significantly slower.

Secondary memory

a non-volatile, persistent and not immediately accessible by a computer or processor. It allows users to store data and information that can be retrieved, transmitted, and used by apps and services quickly and easily.

Secondary Memory Types

hard disk drives; solid state drives (SSDs); Optical (CD or DVD) drives; Tape drives