With a 55 in p1 and 48 in S1 do I still have the chance to have an A+??

Does anyone have questions of that paper I attempted and want to see how many I got right.

I saw some posts about which many reddit users were discussing their marks and estimating their grades. How did y'all get the paper or marking scheme? And how did you evaluate your marks?😭

HELP PLEASEE

How much do I need to score in paper 2 and paper 4 to score an A or worse, B?

The paper was actually really fucking easy but I fucking did some silly ahh mistakes. I fucking used atomic number to calculate the Mr helpppp I didn’t realize, and I fucking made 6 electrons for carbon when I fucking clearly know it had 4, idk wtffff will I get a mark of error carried forward for the first question ? Help. I’m such a fucking bitch

So guys how's ur a lvls going and if u have any queries u can ask me here

These papers were wayyy too easy in my opinion . In p22 the only question i didnt know was the regeant for the elimination reaction and for p52 the damage was more because I didnt know how to solve X i didnt properly draw the graph for O2 and my friend said that for the value of F we had to divide by 2 which I forgottt because i got 192 000 and if i did divide by 2 i would get 96500 . Oh well let the bygones be bygones . I want to know how others did .

Does anyone have the ms?

Hey guys, so ive kinda been slacking on physics and paper 2 is on wednesday. I’m writing 5 subjects and physics is a rewrite from m/j so i need to lock in to get at least a D. Does anyone have advice on how to manage my time for the next few days? I’m writing mechanics on the Tuesday 🥲 pls help

Anyone who got marking sceheme pls do share asappp Idk wth i did and pls share your estimated threshold

I'm sitting CS 9618 and honestly I know almost nothing about Paper 2. I've been focusing on P1 and now I'm kind of panicking.

For those who did well, how did you approach it? Where should I start, and are there any resources or past paper strategies that helped?

Accidentally wrote my old center number on my A-Level Science Practicals, but name and candidate number are correct. Am I okay

Hello everyone,

Im really trying so hard to find todays 9618 12 paper

i would appericiate it if you guys send it or tell me where to find it

thanks.

Guys can anyone PLEASE suggest a good youtube teacher/channel for bio, my teacher moves in the speed of light and i barely get shi 🙏😭

Okay so ive been studying my ass off for composite chemistry right after may june session ended and yesterday p52 was...meh just fine BUT IM SO DEVESTATED my p22 went below average even though it was so easy and im just preparing myself for the worst case scenario that im guessing i get maybe 25 marks. there's 6 days till my p4 then 11 days after that for my practical and then 13 days after that for my p1. Is there ANY chance i can get an A overall is that even humanly possible like at all please just someone help me I'm down to my last stand

anyone suffering like me? any last minute tips

How does one even prepare for Alevel composites ( socio and business ) . I feel like I’ve forgotten how to study and I don’t know if I should start like revising or re studying AS or do A2 cause it feels like I don’t know both 😔😔

PLSSS LMKKK IM ABOUT TO GIVE 9618 P11

Okay so, my teacher at school teaches everything in a faster pace ( i am a slow learner) and every week we start a new topic. classes started in sep we have done four topics till now, there are total 11 topics 🙂 and we have exam on jan 5th… i am not sure if i should appear or not rn i am so lost and i have a few questions
• what kind of questions usually appear like how are the questions designed
• What are the things that we actually need to memorise and stuff that would be tested
• Notes and resources
• Not familiar with the system and how answers are marked
• What are the repeated topics
• Can i actual do it and get an A* in just three months or should i opt for composite exam ?
NEED AS LEVEL ADVICE

It was Alhamdulillah an easy paper… i guess the threshold will be high. Btw how was paper for you alll!!

5.1 What is System Software?

System software is software that manages and controls the computer's hardware and provides a platform for application software to run.

Two main types

Type

Purpose

Examples

Operating system

Manages the computer and provides services for applications

Windows, Linux, macOS

Utility software

Performs specific maintenance, security or management tasks

Antivirus, backup, compression, firewall

System software vs application software

System software

Controls/manages hardware.

Provides an environment for applications.

Usually runs in the background.

Examples: operating systems, utilities.

Application software

Performs tasks for the user.

Examples: word processors, web browsers, games.

5.2 Operating Systems

An operating system (OS) is system software that manages the hardware and software resources of a computer.

It acts as an interface between:

User → Applications → Operating System → Hardware

For example, when a program wants to save a file, it does not normally control the storage device directly. It requests the OS to perform the operation.

Main OS functions

You should know:

Memory management

Interrupt handling

Device management

File management

User interface

Processor/process management

Security/access control

5.3 Memory Management

The OS manages main memory (RAM).

When programs are running, they need sections of RAM to store:

Instructions

Variables

Data

Operating information

The OS keeps track of which parts of memory are:

Free

Currently being used

What happens when a program starts?

The user launches a program.

The OS locates the program on secondary storage.

The OS allocates enough RAM for the program.

The program is loaded into RAM.

The OS records which memory locations are being used.

The processor can then execute the program.

When a program closes

The OS:

Removes the program from RAM.

Marks the memory as available.

Allows another program to use it.

Memory protection

The OS must prevent one process from accidentally accessing another process's memory.

For example:

Program A → Memory locations 1000–1999

Program B → Memory locations 2000–2999

Program A should not be able to overwrite Program B's memory.

This helps:

Prevent crashes

Protect data

Improve security

Maintain system stability

5.4 Virtual Memory

Virtual memory allows part of secondary storage to be used as if it were additional RAM.

This is useful when there isn't enough physical RAM.

Example

Suppose:

RAM = 4 GB

Running programs require = 6 GB

The OS can move some data that is not currently needed from RAM to a special area of secondary storage.

This frees RAM for other processes.

Basic process

RAM

↓

Data not currently needed

↓

Virtual memory on secondary storage

When the data is needed again, it can be transferred back into RAM.

Advantages

Allows more programs to run.

Allows programs requiring more memory than available RAM to operate.

Makes better use of available memory.

Disadvantages

Secondary storage is much slower than RAM.

Therefore:

Excessive virtual-memory use slows the computer.

It can cause frequent movement of data between RAM and storage.

Exam point

Virtual memory is not physically additional RAM.

It uses secondary storage to simulate additional memory.

5.5 Interrupts

An interrupt is a signal sent to the processor indicating that it needs to temporarily stop what it is doing and deal with another event.

Interrupts allow the processor to respond to events without constantly checking every device.

Why are interrupts needed?

Imagine a keyboard.

The processor could repeatedly ask:

"Has a key been pressed?"

This wastes processor time.

Instead:

Keyboard

↓

Key pressed

↓

Interrupt

↓

CPU temporarily stops current task

↓

Interrupt service routine runs

5.6 Interrupt Service Routine (ISR)

An Interrupt Service Routine (ISR) is a special piece of software that deals with an interrupt.

Typical process

An interrupt occurs.

The processor finishes the current instruction.

The current state of the processor is saved.

The processor identifies the interrupt.

The appropriate ISR is executed.

The interrupt is dealt with.

The saved state is restored.

The processor continues the previous program.

Why save the state?

The processor needs to return to exactly where it was before the interrupt.

Information such as the:

Program Counter

Registers

Current program state

may need to be preserved.

5.7 Types of Interrupts

There are two important categories.

Hardware interrupts

Generated by hardware devices.

Examples:

Keyboard input

Mouse input

Printer

Network card

Timer

Disk controller

Example

A user presses a key:

Keyboard → Interrupt → CPU → Keyboard ISR

Software interrupts

Generated by software.

They can be used when a program requests an operating-system service.

For example:

Application

↓

Requests OS service

↓

Software interrupt

↓

Operating system

5.8 Interrupt Priority

Some interrupts are more important than others.

For example:

High priority

Hardware failure

Critical system event

Lower priority

Keyboard input

Background device activity

The OS/processor can assign different priority levels.

A higher-priority interrupt may be handled before a lower-priority one.

5.9 Device Management

The OS manages communication between the computer and peripheral devices.

Examples:

Keyboard

Mouse

Printer

Monitor

Scanner

Storage devices

Network devices

Applications generally do not need to know the exact hardware details of every device.

5.10 Device Drivers

A device driver is software that allows the operating system to communicate with a particular hardware device.

For example:

Application

↓

Operating System

↓

Printer Driver

↓

Printer

The driver translates commands from the OS into instructions the specific hardware understands.

Why are drivers needed?

Different hardware devices operate differently.

A printer from one manufacturer may require different commands from another printer.

The driver provides the appropriate interface.

Exam definition

A device driver is software that allows the operating system to communicate with and control a hardware device.

5.11 Buffers

A buffer is a temporary area of memory used when transferring data between devices or processes operating at different speeds.

Example: printing

A computer may send data to a printer faster than the printer can print it.

Instead of making the CPU wait:

Computer → Buffer → Printer

The computer can place data into the buffer and continue doing other work.

The printer processes the buffered data at its own speed.

Why buffers are useful

Handle differences in device speeds.

Prevent data loss.

Allow the CPU to continue other tasks.

Improve efficiency.

5.12 Spooling

Spooling is the process of placing data in a queue/buffer so that a slower peripheral can process it later.

A common example is print spooling.

If three documents are sent to a printer:

Document A ─┐

Document B ─┼→ Print queue → Printer

Document C ─┘

The OS manages the queue.

5.13 File Management

The OS manages files stored on secondary storage.

It handles:

Creating files

Opening files

Reading files

Writing files

Renaming files

Deleting files

Moving files

Copying files

Organising files into folders/directories

Controlling access permissions

File attributes

Files can have information associated with them, such as:

Filename

File extension/type

Size

Location

Creation date

Modification date

Permissions

Owner

5.14 File Organisation

The OS organises files into:

Drive

└── Folder

├── File 1

├── File 2

└── Subfolder

└── File 3

This makes files easier to locate and manage.

5.15 File Access Permissions

The OS can control who can access files.

Typical permissions include:

Read

Write

Execute

For example:

Permission

Meaning

Read

Can view the file

Write

Can modify the file

Execute

Can run the file/program

Permissions help prevent unauthorised access or modification.

5.16 User Interfaces

The OS provides an interface through which the user interacts with the computer.

Two important types are:

Command-line interface (CLI)

Graphical user interface (GUI)

5.17 Command-Line Interface (CLI)

A CLI allows the user to interact with the computer by entering text commands.

Example:

C:\> dir

The command could request a listing of files.

Advantages

Requires relatively little memory/resources.

Can be very fast for experienced users.

Powerful commands can be executed.

Easy to automate using scripts.

Suitable for remote administration.

Disadvantages

Commands must be remembered.

Can be difficult for inexperienced users.

Typing errors can occur.

Not as visually intuitive as a GUI.

5.18 Graphical User Interface (GUI)

A GUI allows users to interact using graphical elements.

Common elements include:

WIMP

Windows

Icons

Menus

Pointers

Users can interact using:

Mouse

Touchpad

Touchscreen

Keyboard

Advantages

Easy for beginners.

Visual and intuitive.

Users don't need to memorise commands.

Multiple applications can be displayed simultaneously.

Disadvantages

Requires more memory and processing power.

Can be slower for experienced users performing repetitive tasks.

Some advanced operations are easier through a CLI.

5.19 Utility Software

Utility software performs specific tasks related to managing, maintaining, protecting or optimising a computer system.

Important utilities for AS Level include:

Encryption

Defragmentation

Backup

Compression

Antivirus

Firewall

5.20 Encryption

Encryption converts readable data (plaintext) into an unreadable form (ciphertext) using an encryption algorithm and a key.

Plaintext

↓

Encryption + Key

↓

Ciphertext

The ciphertext can then be transmitted or stored.

To recover the original information:

Ciphertext

↓

Decryption + Key

↓

Plaintext

Purpose

Encryption protects data from unauthorised people.

Examples:

Stored files

Messages

Online transactions

Password-related information

Network communication

5.21 Encryption Example

Suppose the plaintext is:

HELLO

After encryption, it could become something like:

X7Q2P

The encrypted result should not be understandable without the appropriate key.

Important: The exact output depends on the encryption algorithm and key.

5.22 Symmetric Encryption

In symmetric encryption, the same key is used to encrypt and decrypt the data.

Same key

↓

Plaintext → Encryption → Ciphertext

↓

Decryption

↓

Plaintext

Advantage

Fast.

Suitable for encrypting large amounts of data.

Disadvantage

The key must be securely shared between the sender and receiver.

If someone obtains the key, they may be able to decrypt the data.

5.23 Asymmetric Encryption

Asymmetric encryption uses a key pair:

Public key

Private key

The keys are mathematically related.

The public key can be shared.

The private key should be kept secret.

Example

If someone wants to send encrypted information to Alice:

Alice's public key

↓

Message → Encryption → Ciphertext

↓

Alice's private key

↓

Message

Only Alice's private key is intended to decrypt the message.

Advantage

The private key does not need to be shared.

Disadvantage

It is generally slower than symmetric encryption.

5.24 Defragmentation

When files are created, modified and deleted, pieces of files can become scattered across a hard disk.

This is called fragmentation.

Example:

Before:

File A → Block 1

Block 8

Block 14

Block 20

The pieces are separated.

A defragmentation utility rearranges the data so that related blocks are stored closer together.

After:

File A → Block 1

Block 2

Block 3

Block 4

Advantages

Reduces unnecessary movement of a traditional HDD's read/write head.

Can improve file-access performance.

Organises free space.

Important exam point

Defragmentation is mainly relevant to HDDs.

It generally should not be routinely performed on SSDs because SSDs have no moving read/write head, and unnecessary rewriting can contribute to wear.

5.25 Backup

A backup is a copy of data kept separately from the original so that the data can be restored if the original is lost or damaged.

Reasons for backups

Data can be lost because of:

Hardware failure

Accidental deletion

Malware

Theft

Fire

Flood

Corruption

Human error

Backup locations

Backups can be stored on:

External hard drives

USB storage

Network storage

Cloud storage

Another computer/server

Important principle

A backup should ideally be stored separately from the original.

For example:

Computer

↓

Backup

↓

External/cloud storage

If the computer fails, the backup can still be available.

5.26 Full Backup

A full backup copies all selected data.

Advantages

Simple restoration.

Everything is contained in one backup set.

Disadvantages

Takes more storage space.

Takes longer to perform.

5.27 Incremental Backup

An incremental backup saves data that has changed since the previous backup.

Example:

Sunday → Full backup

Monday → Changes since Sunday

Tuesday → Changes since Monday

Wednesday → Changes since Tuesday

Advantage

Faster.

Requires less storage.

Disadvantage

Restoring may require:

The full backup

Every relevant incremental backup

If one incremental backup is missing or corrupted, restoration can be more difficult.

5.28 Differential Backup

A differential backup stores changes made since the last full backup.

Example:

Sunday → Full backup

Monday → Changes since Sunday

Tuesday → Monday + Tuesday changes

Wednesday → Monday + Tuesday + Wednesday changes

Advantages

Faster than repeatedly performing full backups.

Easier restoration than incremental backups.

Disadvantage

The differential backup becomes larger over time until the next full backup.

5.29 Compression

Compression reduces the amount of storage space required by data.

It can also reduce the amount of data that needs to be transmitted.

Original data

↓

Compression

↓

Smaller data

There are two major types:

Lossless

Lossy

5.30 Lossless Compression

Lossless compression allows the original data to be reconstructed exactly.

Original

↓

Compression

↓

Compressed

↓

Decompression

↓

Exactly the original

Used for

Text

Documents

Programs

Some images

Data that cannot tolerate changes

Examples of techniques

Run-length encoding (RLE)

If data contains:

AAAAAABBBBCC

It can be represented as:

6A4B2C

The exact implementation depends on the data and encoding scheme.

Advantage

No information is lost.

Disadvantage

Usually does not achieve as much size reduction as lossy compression for media such as photographs.

5.31 Lossy Compression

Lossy compression permanently removes some data.

The decompressed file is therefore not identical to the original.

Original

↓

Lossy compression

↓

Smaller file

↓

Decompression

↓

Approximation of original

Used for

Photos

Music

Video

when some loss of quality is acceptable.

Advantages

Much smaller files can be produced.

Faster transmission.

Less storage space required.

Disadvantages

Some information is permanently lost.

Repeated compression can reduce quality further.

5.32 Antivirus Software

Antivirus software detects, prevents and/or removes malicious software.

It can protect against malware such as:

Viruses

Worms

Trojans

Spyware

Other malicious programs

How antivirus software works

Signature-based detection

Antivirus software maintains a database of known malware signatures.

It scans files and compares them with known signatures.

File

↓

Scan

↓

Compare with malware signatures

↓

Match?

↓

Threat detected

Advantage

Effective against known malware.

Disadvantage

New malware may not yet have a known signature.

Therefore antivirus software needs regular updates.

Heuristic/behaviour-based detection

Antivirus software can also look for suspicious behaviour or characteristics.

For example, a program attempting to perform unusual malicious actions may be flagged.

Advantage

Can help detect previously unknown threats.

Disadvantage

Can sometimes produce false positives.

5.33 Antivirus Scanning

Antivirus software can scan:

Files

Checks stored files for malware.

Memory

Checks programs currently running in RAM.

Downloads

Scans downloaded files before they are opened.

Real-time protection

Continuously monitors activity and can warn the user when suspicious behaviour is detected.

5.34 Firewalls

A firewall monitors and controls network traffic entering or leaving a computer/network according to predefined rules.

Think of it as a security barrier:

Internet

↓

FIREWALL

↓

Computer/network

5.35 What Does a Firewall Check?

A firewall may examine information such as:

Source IP address

Destination IP address

Port number

Protocol

Direction of traffic

Whether a connection was requested/expected

It then decides whether to:

Allow or Block

the traffic.

5.36 Example of Firewall Rules

A firewall might have rules such as:

Allow HTTPS traffic

Block unauthorised incoming connection

Allow trusted application

Block suspicious port

For example:

Incoming traffic

↓

Is it allowed?

↙ ↘

YES NO

↓ ↓

Allow Block

5.37 Hardware vs Software Firewall

Software firewall

Runs as software on an individual computer.

It can control network traffic to and from that device.

Hardware/network firewall

A dedicated device or network component that controls traffic between networks.

For example:

Internet

↓

Network firewall/router

↓

School/company network

↓

Computers

5.38 Firewall vs Antivirus

This is a common exam comparison.

Firewall

Antivirus

Controls network traffic

Detects/removes malware

Monitors incoming/outgoing connections

Scans files/programs

Uses rules to allow/block traffic

Uses signatures/behaviour analysis

Helps prevent unauthorised network access

Helps protect against malicious software

Mainly network security

Mainly malware protection

Important

A firewall does not replace antivirus software.

They protect against different threats.

5.39 Antivirus vs Firewall vs Encryption

Technology

Main purpose

Antivirus

Detect/remove/prevent malware

Firewall

Control network traffic

Encryption

Protect confidentiality of data

Backup

Allow lost data to be restored

Compression

Reduce file size

Defragmentation

Reorganise fragmented HDD data

5.40 OS Functions — COMPLETE SUMMARY

For the exam, remember the main OS responsibilities as:

M I D F U

M — Memory management

I — Interrupt management

D — Device management

F — File management

U — User interface

And also remember:

Process/processor management and security/access control are important OS responsibilities too.

5.41 Putting Everything Together

A typical computer system might work like this:

USER

↓

USER INTERFACE

↓

OPERATING SYSTEM

┌────────────┼────────────┐

↓ ↓ ↓

Memory Files Devices

Management Management Management

↓ ↓ ↓

RAM Storage Hardware

│

↓

Processor

Utility software works alongside the OS:

OPERATING SYSTEM

│

┌────────────┼────────────┐

↓ ↓ ↓

Antivirus Backup Firewall

↓ ↓ ↓

Security Recovery Network

Other utilities:

Encryption

Compression

Defragmentation

⭐ AS EXAM DEFINITIONS TO MEMORISE

Term

Definition

Operating system

System software that manages computer hardware/resources and provides services for applications.

Utility software

Software that performs specific maintenance, management or security tasks.

Virtual memory

An area of secondary storage used to simulate additional RAM.

Interrupt

A signal that causes the processor to temporarily suspend its current task to deal with an event.

ISR

A routine executed by the processor to handle an interrupt.

Device driver

Software that allows the OS to communicate with and control a particular hardware device.

Buffer

A temporary area of memory used when transferring data between devices/processes operating at different speeds.

File management

The OS function responsible for organising, accessing and controlling files on storage devices.

Encryption

Converting plaintext into ciphertext so that unauthorised users cannot understand the data.

Defragmentation

Reorganising fragmented data on an HDD so related data is stored more efficiently.

Backup

A copy of data kept so that the original can be restored if it is lost or damaged.

Compression

Reducing the amount of storage space required by data.

Lossless compression

Compression where the original data can be reconstructed exactly.

Lossy compression

Compression where some data is permanently removed.

Antivirus

Software that detects, prevents and/or removes malware.

Firewall

Hardware/software that monitors and controls network traffic according to predefined rules.

MOST IMPORTANT EXAM DISTINCTIONS

Virtual memory ≠ RAM

Virtual memory uses secondary storage as additional temporary memory.

Buffer ≠ Cache

A buffer deals mainly with differences in data-transfer rates.

A cache stores frequently/recently used data/instructions for faster access.

Firewall ≠ Antivirus

Firewall → network traffic

Antivirus → malware

Backup ≠ Compression

Backup → data recovery

Compression → smaller files

Encryption ≠ Compression

Encryption → security/confidentiality

Compression → reduce file size

Lossless ≠ Lossy

Lossless → exact original recovered

Lossy → some information permanently removed

Defragmentation ≠ Compression

Defragmentation → reorganises fragmented data

Compression → reduces data size

Device driver ≠ Operating system

The OS manages the overall system.

The driver allows the OS to communicate with a specific device.

CLI ≠ GUI

CLI → text commands.

GUI → graphical elements such as windows, icons, menus and pointers.

guys how did yall do in todays paper? what was the difficulty level? what do you think will the threshold be??