ROM RAM and Virtual Memory  Lesson Objective: Understand the difference between ROM, RAM and the purpose of Virtual Memory  Learning Outcome: Define the key words and give a brief explanation for each. Explain the workings of virtual memory Keywords: ROM, RAM, Virtual memory, volatile, non-volatile

What is ROM?  ROM is Read Only Memory  It does not need power to ‘remember’ so it is called non-volatile memory  It cannot change once written  One purpose of ROM in a PC is to store the boot sequence program to start the computer.

So what does ROM look like?? BIOS is an example of ROM in a PC. The program stored in ROM looks like this when it runs If ROM doesn’t need power, why do we have a battery? This is just one example of ROM used in IT. After the data is written it cannot be changed or erased. (Don’t get it mixed up with CD-RW)

(Not needed for the exam!) ROM, BIOS and CMOS Some of the important settings of a computer needs to be changeable and therefore needs to be held in RAM This RAM is what needs the battery to ‘remember’ the settings. It uses a power-efficient memory called CMOS (Complementary Metal Oxide Semiconductor Field Effect Transistor) The internal clock also needs power to hold the time and date (as does any clock!)

What is RAM?  Random Access Memory  It loses it’s memory when it has no Power, therefore it is Volatile memory.  The amount of RAM is important for the speed of a computer. Some applications need more RAM than others.

So what does it look like? RAM can be easily replaced on the motherboard of a computer

How much RAM do you need? Software usually comes with system requirements which specifies the amount of RAM needed as well as other requirements. (Physical Memory = RAM)

How much RAM? (Low, Medium, High, V. High) Text editor e.g. to write a short computer program. Text editor e.g. to write a short computer program. Graphics editor e.g. to edit a 5mb photo Graphics editor e.g. to edit a 5mb photo LOW Medium

How much RAM? (Low, Medium, High, V. High) Computer game with animations Video editor e.g. to edit a 30 min video Video editor e.g. to edit a 30 min video V. High High / V.High

How much RAM? (Low, Medium, High, V. High) DTP software to make a 64 page magazine Database to store the addresses of every dwelling in London High Medium

Word processor to write a letter Low How much RAM? (Low, Medium, High, V. High)

Using RAM

What happens if there isn’t enough RAM to do everything? 0.5 GB 1 GB 1.5 GB 2 GB Word Processor Text editor Video Editor Database Graphic Editor Unused programs and data will move to virtual memory Space is now available for the new program and data RAM Super- fast! Virtual Memory- Setting aside space on a hard disk as RAM “overflow” Virtual Memory (On Hard disk=slow) 10 GB Programs are swapped in and out of VM as needed. If there is not enough RAM for common use VM has to be constantly used and this SLOWS DOWN the performance of the computer.

Workbooks!