OCR J277 Systems Software

Lesson 2: Memory & Multitasking

How the OS keeps track of data and balances multiple apps.

Lesson Progress

0/5
01 Review of Previous Learning

DO NOW: Memory Recap

In Unit 1.2, we looked at RAM and ROM. Recall their roles below to prepare for today's OS focus.

RAM

Temporary storage for the OS, apps, and data currently in use. Volatile.

Secondary Storage

Permanent storage for files and software. Non-volatile (e.g. SSD, HDD).

Critical Connection: Today we learn how the Operating System acts as the traffic warden, moving data between these two locations and the CPU.
02 Introducing the New Objective & KWs

Context & Keywords

Learning Objective

To explain how the Operating System manages memory allocation and data transfer to enable multitasking.

Tier 3 Vocabulary (Click to flip):

Allocation Click to enlarge

The process where the OS assigns specific blocks of RAM to programs when they start up.

Word
OS
Free
Free

"You take Block A, you take Block B."

Click to close
Data Transfer Click to enlarge

Moving instructions and data between RAM and the CPU for processing.

RAM
CPU

Continuous flow of instructions.

Click to close
Multitasking Click to enlarge

The ability to run multiple apps at once by swapping between them so fast they seem to run simultaneously.

App 1
App 2
App 3

Rapid CPU swapping.

Click to close
03 New Learning

How it Works: Memory & Multitasking

1. Memory Protection (Allocation)

When you open an app (e.g. Spotify), the OS assigns it a unique area of RAM. The OS ensures that **App A cannot access the data of App B**. This prevents crashes and keeps data secure.

Excel (2GB)
Chrome (4GB)
Remaining Free RAM

2. The Illusion of Simultaneity

Most CPUs can only do ONE thing at a time. The OS enables multitasking by:

  • Step A

    Allocating time-slices of the CPU to each running process.

  • Step B

    Swapping processes in and out of the processor incredibly quickly.

  • Step C

    The user perceives all programs as running at exactly the same time.

04 Application

Independent Task & Exam Practice

Task 1: The Memory Management Lab

  • Open the Memory_Simulator.html link shared in Google Classroom.
  • Launch the required apps and observe how the OS **allocates** space.
  • Reach a "Stable State" with 4 apps running without a system crash.
  • Screenshot your completed RAM grid and paste it into your Google Doc.

Task 2: Exam Question

In your Google Doc, answer the following 3-mark OCR exam question.

"Explain how an operating system manages memory to allow for multitasking." (3 Marks)
Show Mark Scheme Hint
1 Mark: Mentions memory allocation / assigning space.
1 Mark: Mentions swapping processes in/out of the CPU.
1 Mark: Mentions protecting memory (stopping apps overwriting each other).
05 Consolidation

Plenary: True or False?

"The OS allows two apps to share the exact same memory blocks."

FALSE

"Multitasking works by the OS swapping apps in and out of the CPU quickly."

TRUE

"Allocation is the process of deciding which files are saved to the SSD."

FALSE

Lesson Complete!

You now understand how the OS manages the brain of the computer.

Return to Hub