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Computer Systems. Nat 4/5 Computing Science Section 2 Computer Structure: Lesson 6: Memory. 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 .

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computer systems

Computer Systems

Nat 4/5 Computing Science

Section 2 Computer Structure:

Lesson 6: Memory

lesson aims
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
a quick recap
Nat 4/5A quick recap
  • We are going to look at the Backing Storage and Memory

Backing Storage

Processor

Input Devices

Output

Devices

Memory

main memory
Nat 4/5Main Memory

Main Memory

  • Main memory falls into two types:
  • RAM
    • Random Access Memory
  • ROM
    • Read Only Memory

RAM

ROM

ram r andom a ccess m emory
Nat 4/5RAM – 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.
rom r ead o nly m emory
Nat 4/5ROM – 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
Nat 4/5Addressability
  • Your house has a unique address, made up of street, town and postcode.
    • No two houses have the same address!
  • This is the same for memory in the computer
    • Memory is made up of thousands of millions of storage locations
    • Each storage location in memory has it’s own unique address so that the processor can locate it
    • This address is a binary value
      • e.g 1110100100101001
backing storage
Nat 4/5Backing 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
Summary

RAM (Random Access Memory)

  • Is used to store programs and the operating system
  • Is volatile, which means it loses its 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

questions
Questions
  • How can the processor identify each location in memory?
  • What type of memory stores the programs that the user is currently using?
  • What type of memory stores essential programs that make the computer work?
  • What type of memory is volatile?
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