OCR J277 Mark Scheme

OCR	GCSE (9-1) Computer Science Mark Scheme J277/01: Unit 1.5.2 Utility Software

Question	Answer	Marks	Guidance
1a	Email large folder: Compression Prevent thieves reading diary: Encryption Loading files slowly: Defragmentation Archive old invoices: Compression	4	1 mark per correct row. If multiple boxes ticked in one row, award 0.
1b	To perform housekeeping or maintenance tasks (1). To keep the computer running smoothly/efficiently (1).	1	Reject: Specific examples (e.g., "To defrag the disk") as the general purpose.
2a	Transmission Speed: The file will upload/download faster because it is smaller (1). Data Usage: It uses less bandwidth/data allowance to send (1). Storage limits: It is more likely to meet the email provider's attachment size limit (1).	2	Max 2 marks.
2b	Accuracy: Lossless compression keeps all original data / restores the file exactly to its original state (1). Consequence: If Lossy were used, text characters or code might be deleted/altered, making the coursework unreadable or the code invalid (1).	2
2ci	It uses an algorithm to remove data that is considered unnecessary or redundant (1). Example: Removing colours that the human eye cannot distinguish / reducing the number of pixels (1).	2
2cii	The quality of the image will be lower (pixelated/blurrier). (1)	1
3a	The software uses an algorithm (or cipher) to scramble (or encode/mix up) the data (1). A key is required to decrypt/unscramble it (1).	3	Must reference algorithm/scrambling and key.
3b	Correction: Encryption does not stop files from being intercepted, stolen, or deleted (1). Achievement: It ensures that if the data is stolen, it is meaningless / unreadable / cannot be understood by the thief (1).	2	Reject: "cannot be read" (it can be read, just not understood). Reject: "uses a lock".
4a	When files are deleted, gaps appear on the disk (1). When new files are saved, if they are larger than the gaps, the OS splits the file up (1) and saves the parts in different available spaces (1).	2
4b	It analyses the disk to find split files (1). It moves the file segments so they are stored contiguously (or consecutively / together) (1). It groups all the free space together (1).	3
4c	The read/write head (1) does not have to move as far physically across the disk surface (1) to read the next part of the file.	2	Do NOT award: "It makes the computer faster" (too vague) or "It creates more space" (incorrect).
4d	SSDs have no moving parts / random access speed is the same regardless of location / it can wear out the SSD (limited read/writes).	1
5	Algorithm Key Original Permanent Separate Contiguous Read/Write Head Space	8	1 mark per correct word.