Page 87 - Computer_Science_F5

Computer Science Turning off the stove (halt): This instruction puts the processor

into a low-power state, effectively stopping all program
execution. It is like the head chef turning off the stove (halting
operations) when the kitchen is closed.
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(b) Why is it important to restrict access to privileged instructions? Think about
potential consequences if junior cooks had unrestricted access to all ingredients
and appliances.

(c) A new recipe (user program) requires deep-frying (privileged operation) a
specific ingredient. How can the junior cooks (user program) achieve this task
securely and efficiently, following the access control protocols of the kitchen
(CPU)?

Function of memory and I/O user programs cannot execute their tasks
system without accessing data stored in memory.
Recall the previous analogy of a restaurant
kitchen (CPU) where the head chef I/O System: The delivery entrance and
(operating system) leads a team of cooks exit
(user programs) to prepare delicious meals The I/O system functions like the kitchen’s
delivery entrance and exit. It handles the
(processed data). To function smoothly, flow of ingredients (data) from external
this kitchen relies on two critical systems: sources (like refrigerators and freezers)
memory and the Input/Output (I/O) and delivers prepared meals (processed
system. data) to customers (external devices).

Similar to how cooks would not have
Memory: The well-stocked pantry everything they need readily available in
Memory acts like the kitchen’s well- the pantry, user programs often require data
stocked pantry, storing all the ingredients from external devices like hard drives or
(data) required for the cooks to prepare network cards. The I/O system facilitates
dishes (programs). The head chef carefully this communication, ensuring a smooth
organises the pantry (memory) to ensure exchange of information. Additionally,
ingredients (data) are easily retrievable the I/O system is crucial for delivering
when needed. This organisation often the final results (processed data) generated
involves techniques like paging and by the user programs. This could involve
sending data to a display screen (like
segmentation, similar to categorising serving a dish to a customer) or storing it
ingredients on shelves or in labelled on a storage device (like packing leftovers
containers. Just like cooks cannot prepare for takeaway). In essence, memory and
a meal without the necessary ingredients, the I/O system work together seamlessly

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for Advanced Secondary Schools

Computer Science Form 5.indd 78 23/07/2024 12:33