Computer Systems Nat 4/5 Computing Science Section 2 Computer Structure: Lesson 2 : Memory

Lesson Aims By the end of this lesson: Pupils will be able to: Describe the difference between main memory and backing storage Describe some of the features and uses of RAM and ROM Describe what is meant by a memory address

Nat 4/5 A quick recap Memory Processor Input Devices Output Devices Backing Storage ROM RAM We are going to look at the Backing Storage and Memory

Main Memory Main memory falls into two types: RAM RAM ROM Nat 4/5 Main Memory Main Memory Main memory falls into two types: RAM Random Access Memory ROM Read Only Memory RAM ROM

RAM – Random Access Memory Nat 4/5 RAM – Random Access Memory Nothing to do with male sheep! RAM is the computers short term memory. If a machine is quoted as having 2GB of Ram then it has 2GB into which programs and the operating system are loaded into. RAM is volatile. This means that it requires power to store data. When power is lost the contents of RAM are lost.

ROM – Read Only Memory There is a problem with just having RAM. Nat 4/5 ROM – Read Only Memory There is a problem with just having RAM. If the contents of RAM are lost then the power is Iost how does the computer know what to do when it switches on? ROM (Read Only Memory) is memory that will always retain its contents even when power is lost. This concept can be used by mobile phones to store their operating systems.

Addressability Your house has a unique address Nat 4/5 Addressability Your house has a unique address No two houses have the same address! This is the same for memory Each location has a unique address

Nat 4/5 Backing Storage Backing storage are devices used to store permanent copies of our files. Examples are such as: Hard Disk Drives USB Flash Drives Magnetic Tapes CD/DVD R/RW At this point in the course knowing their purpose is sufficient. More on these later!

Summary RAM (Random Access Memory) ROM (Read Only Memory) Nat 4/5 Summary RAM (Random Access Memory) Is used to store programs and the operating system Is volatile, it loses contents when there is no power ROM (Read Only Memory) Contents cannot be changed and does not require power to hold data Backing Storage devices are used to store permanent copies of our files and data