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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 4/5

A quick recap

  • We are going to look at the Backing Storage and Memory

Backing Storage

Processor

Input Devices

Output

Devices

Memory


Main memory

Nat 4/5

Main 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 4/5

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.


Rom r ead o nly m emory

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

Nat 4/5

Addressability

  • 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 4/5

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

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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