Virtual Memory

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Running out of Memory

There are many approaches that we might take when we are running low on memory:

Installing more Random-Access Memory

When we run out of RAM, we can purchase and install more RAM so that we can store more data.
This is not always ideal because:
- RAM can be expensive.
- We may only need more memory on a temporary basis.

Virtual memory

Virtual Memory is a technique where we use secondary storage as if it were RAM.
Virtual memory is not always ideal since:
- Virtual Memory can have negative impacts on performance.
- Virtual Memory can have negative impacts on the health of Solid State Disks (SSDs).
- We might have limited space in secondary storage.

Terminating processes

Each program/process will use a certain amount of memory.
By closing some processes that we are not using, we can free the memory that they are using.
This is not always possible because we may need all the processes.

How Virtual Memory Works

Virtual Memory allows us to access more memory than we have by setting aside some secondary storage space to act as extra memory.

Paging

Memory can be split into sections called 'pages'.
Virtual Memory works by moving these pages between the Random Access Memory (RAM) and the secondary storage.

Move pages to Hard Disk Drive (HDD)

If a page is not being used, then we might want to put it into Virtual Memory.
When a page is moved to the HDD and not being used, it is put into a special file called the pagefile.
Other processes can then use the memory that we just freed in the RAM.

Move pages to RAM

When we want to use a page again, we first need to move it back to the RAM.
We do this by swapping the page that we want with one that is already in the RAM.

1Components of a Computer

1.1Structure & Function of the Processor

1.1.1Structure of the CPU

1.1.2Fetch, Decode, Execute Cycle

1.1.3Factors Affecting CPU Performance

1.1.4CPU Architecture

1.2Types of Processors

1.2.1CISC & RISC

1.2.2Multicore & Parallel Cores

1.3Input, Output & Storage

1.3.1Computer Systems

1.3.2Magnetic Storage

1.3.3Optical Storage

1.3.4Types of Optical Storage

1.3.5Types of Memory

1.3.6Flash Memory

1.3.7Virtual Memory

2Software & Software Development

3Exchanging Data

4Data Types, Data Structures & Algorithms

4.1Data Types

4.1.1Data Types

4.1.2Arrays & Strings

4.1.3Representing Numbers

4.1.4Binary Arithmetic

4.1.5Hexadecimal

4.1.6Converting Binary Numbers

4.1.7Floating Points in Binary

4.1.8Floating Point Arithmetic

4.1.9Bitwise Manipulation

4.1.10Character Sets

4.2Data Structures

4.2.1Arrays, Linked Lists & Queues

4.2.2Graphs, Hash Tables & Stacks

4.2.3Trees

4.3Boolean Algebra

4.3.1Computational Logic

4.3.2Boolean Logic

4.3.3Karnaugh Maps

4.3.4Boolean Identities

4.3.5Flip Flops & Adder Circuits

5Legal, Moral, Cultural & Ethical Issues

5.1Computing Related Legislation

5.1.1Data Protection Act (1998)

5.1.2Computer Misuse Act (1990)

5.1.3Copyright Designs and Patents Act (1988)

5.1.4Regulation of Investigatory Powers Act (2000)

5.2Moral & Ethical Issues

5.2.1Online Activity Tracking

5.2.2Censorship

5.2.3Cultural Issues

5.2.4Environmental Issues

5.2.5Layout, Colour Paradigms & Character Sets

6Elements of Computational Thinking

6.1Thinking Abstractly

6.1.1Abstraction

6.2Thinking Procedurally

6.2.1Decomposition

6.3Thinking Logically

6.3.1Pseudocode & Flow Diagrams

7Problem Solving & Programming

7.1Programming Techniques

7.1.1Programming Fundamentals

7.1.2Modularity

7.2Programming Construction

7.2.1Integrated Development Environments

7.2.2Testing

8Algorithms

8.1Algorithms

8.1.1Interpreting, Correcting & Completing Algorithm

8.1.2Sort Algorithms

8.1.3Insertion & Merge Sort

8.1.4Search Algorithms

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