Edexcel GCSE Computer Science (1CP2) Exam Questions

Award up to two marks for a linked description such as:

• It keeps a record of which memory addresses/areas belong to each program and to the operating system (1) so it knows which addresses a program is allowed to use (1)
• Each program is given its own area of main memory (1) so a program cannot write to the addresses used by another program or by the operating system (1)
• The memory used by the operating system is marked as protected/reserved (1) so a program that tries to write to it is blocked/causes an error (1)
• The address a program writes to is checked against the record of its allocated area (1) and the write is stopped if the address is outside that area (1)

Allow the memory being protected to be that of the operating system or of another program.

For both marks, the expansion must follow/associate with the statement.

Do not award generic answers such as 'the operating system manages memory' or 'the operating system keeps track of memory'.

Do not award responses about stopping programs using too much memory or allocating memory, as these are not about protecting memory being overwritten.

Do not award responses about virtual memory, paging or moving processes to secondary storage.

Do not award responses about firewalls, antivirus software or passwords.

Award up to two marks for a linked description such as:

• Allocates memory/RAM to the process (1) so its instructions and data can be stored (1)
• Loads/moves the program instructions into RAM (1) so the process is ready to run (1)
• Adds the process to the ready queue (1) so it can be scheduled onto the CPU (1)
• Gives the process a process ID (PID)/identifier (1) so the operating system can track/manage it (1)

For both marks, the development must follow/be linked to the point.

Only award one of the first two bullets in any one response; allocating memory and loading into RAM are the same stage.

Accept 'memory' for 'RAM' and vice versa.

Accept 'added to a queue for the processor' for the ready queue point.

Do not accept responses that say the process is run on the CPU straight away.

Do not accept descriptions of the program executing/running its instructions, or of the program file being created/saved.

Do not accept responses about the process being blocked or terminated.

Award up to two marks for a linked description such as:

• Each user/file is given permissions/access rights (1) so other users cannot read/write/open/change that user's files (1)
• A user may be given read-only/read access to a file (1) so they cannot edit/delete/change it (1)
• Each file is given permissions/access rights for different users (1) so the operating system allows/refuses access depending on which user is logged in (1)
• The operating system checks a user's permissions/access rights when a file is opened (1) so a user with read-only/read access cannot save/delete changes (1)

Do not accept responses about asking for a password/username, as this checks who the user is, not what they are allowed to do.

Do not accept 'files are protected/safe' or 'access rights protect files' without saying how access is limited (e.g. read-only access, permissions for different users).