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

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

3. A quick recap  We are going to look at the Backing Storage and Memory Nat 4/5 Processor Input Devices OutputDevices Memory Backing Storage

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

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 is loaded into.  RAM is volatile.  This means that it requires power to store data.  When power is lost the contents of RAM are lost. Nat 4/5

6. 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 ( R ead O nly M emory) 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. Nat 4/5

7. Addressability  Your house has a unique address  No two houses have the same address!  This is the same for memory  Each location in the computer’s memory has it’s own unique address (in binary) Nat 4/5

8. 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. Nat 4/5

9. 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 Nat 4/5