Document page
Computer Science IGCSEPDF 8
142 pagesrevision 46930
PDF 8
Page image rendered from the stored file at 110 dpi; it sharpens as you zoom. Outlines are placed from each region’s stored position on the page (612 × 792 pt).
readable
Source of this text: embedded text layer. The better of the embedded text and OCR is kept.
Lossy Compression
Removes data permanently to reduce file size.
Key Terms Summary
1.6 File Management
File management organizes and maintains files within storage systems.
1.5 Data Compression
Purpose: To reduce file size for faster transfer and storage.
Lossless Compression
No data lost; file can be perfectly restored.
Run Length Encoding (RLE)
Replaces repeated data with count + value.
Used for text, spreadsheets, software, PNG, ZIP, FLAC.
Used in JPEG, MP3, MP4.
Methods: cropping, reducing colour depth, reducing sample rate/bit depth.
Lossy is irreversible but achieves much smaller file sizes.
-Operating System manages files and permissions.
-File naming includes extensions (.txt, .jpg, .docx).
-Hierarchical structure: root → folders → subfolders → files.
-Paths: absolute or relative.
-Metadata: file size, type, creation date, author, permissions.
Note: File management is no longer in Chapter 1, but covered in Chapter 4.
Example: AAAAA → 5A
Used for text (repeated letters), images (pixels), and sound (silent samples).