Be able to reduce file sizes for storage or transmission where necessary using file compression including .zip, .rar

Published by Patrick Mutisya · 14 days ago

Cambridge IGCSE ICT 0417 – File Management: Reducing File Sizes with Compression

File Management – Reducing File Sizes for Storage or Transmission

Why Reduce File Sizes?

Large files can cause several problems:

  • Limited storage space on devices or servers.

  • Longer upload and download times, especially on slow connections.

  • Higher costs for data transfer and cloud storage.

  • Potential incompatibility with email attachment size limits.

What Is File Compression?

File compression is the process of encoding information using fewer bits than the original representation. The result is a smaller file that can be stored or transmitted more efficiently. Compression can be:

  • Lossless – original data can be restored exactly (e.g., ZIP, RAR).

  • Lossy – some data is permanently discarded to achieve higher reduction (e.g., JPEG, MP3). For document and program files, lossless compression is required.

Common Compression Formats

The two most widely used lossless archive formats in ICT examinations are .zip and .rar.

Comparing .zip and .rar

Feature.zip.rar
Typical compression ratioModerate (≈ 2‑3 : 1)Higher (≈ 3‑5 : 1)
Native support in operating systemsBuilt‑in (Windows, macOS)Requires third‑party software (e.g., WinRAR, 7‑Zip)
Ability to split archivesLimitedFull support for multi‑volume archives
EncryptionBasic password protection (ZIP‑Crypto)Strong AES‑256 encryption
Recovery recordsNoYes – can repair damaged archives

How to Create a .zip Archive (Windows)

  1. Select the files or folders you wish to compress.

  2. Right‑click the selection and choose Send to → Compressed (zipped) folder.

  3. A new file with the .zip extension appears in the same location.

  4. Rename the archive if required.

How to Create a .rar Archive (Using WinRAR)

  1. Install WinRAR (or a compatible program).

  2. Select the files/folders to compress.

  3. Right‑click and choose Add to archive….

  4. In the dialog box:

    • Set Archive format to RAR.

    • Choose a Compression level (e.g., Best).

    • Optionally set a password for encryption.

    • If the archive is large, enable Split to volumes and specify a size.

  5. Click OK to create the .rar file.

Extracting Files from an Archive

Both Windows and most archive utilities allow you to extract files:

  • For .zip: double‑click the archive and drag the contents out, or right‑click → Extract All….

  • For .rar: open with WinRAR and click Extract To, or use a compatible free tool such as 7‑Zip.

Best Practices for Using Compression in ICT Projects

  1. Use lossless compression for documents, spreadsheets, presentations, and program files.

  2. Choose .zip when you need maximum compatibility across different computers.

  3. Choose .rar when you need higher compression, password protection, or the ability to split large archives.

  4. Always keep an original copy of important files before compressing, in case the archive becomes corrupted.

  5. Test the archive after creation by extracting a few files to ensure integrity.

Common Pitfalls

  • Attempting to compress already compressed files (e.g., JPEG images, MP3 audio) yields little size reduction.

  • Forcing a high compression level can increase processing time without significant benefit.

  • Relying on a single archive format may cause compatibility issues when sharing with users on different platforms.

Suggested diagram: Flowchart showing the steps from selecting files → choosing compression format → setting options → creating archive → testing extraction.

Summary Checklist

  • Identify files that need size reduction.

  • Decide between .zip (compatibility) and .rar (higher compression, security).

  • Use the appropriate software to create the archive.

  • Verify the archive by extracting a sample.

  • Store the original files safely and keep a backup of the archive.