Question
State three operating system resource management techniques.
▶️Answer/Explanation
Ans:
scheduling;
policies;
multitasking;
virtual memory;
paging;
interrupt;
polling;
Question
Explain how an operating system manages peripherals.
▶️Answer/Explanation
Ans:
OS keeps tracks of all peripheral devices (the I/O controller) / decides which process gets the device when and for how much time / allocates and de-allocates devices;
OS works with device drivers and the basic input/output system (BIOS) to perform hardware tasks
/ the necessary drivers (for every peripheral) are built into the OS and/or when a new peripheral is added software / device driver provided by a hardware maker is installed into the operating system (to tell the computer’s OS how to work with the peripheral/hardware) (because without a device driver the OS would not be able to communicate with this peripheral device);
A device driver translates the OS’s instructions into a language (analogue signals) that the device can understand;
There are various types of device drivers for peripherals (such as keyboards, mice, disk drives, controllers, printers, graphics cards, ports, etc.);
Device drivers run in the OS kernel space (in the part of the OS that directly interacts with the physical structure of the system) (and implement functions such as open, close, read, write);
The running application/user’s program can make a call to device driver functions which provide an interface between user space and kernel space;
Example answer:
An OS manages peripherals via their respective drivers;
For example, sound card drivers;
are necessary so the OS knows exactly how to translate the 1s and 0s (that comprise the MP3 file) into audio signals;
that the sound card can output to headphones / speakers;
Question
A business has a range of different computers within the organization, including laptops, desktops and file servers. Wherever possible the organization uses a common operating system on its computers.
Memory requirements and processor speed will vary depending on the tasks required of the computer.
The business has decided to implement a computer-based system to switch the room lights on and off automatically. The lights will only be switched on if the level of light is below a specific reading and there are people in the room. The lights will be switched off when the room has been unoccupied for at least five minutes.
a.)Outline two resource management techniques that are likely to be carried out by the operating system of a desktop computer.[4]
b.)Outline one way the operating system hides the complexity of the hardware from the computer user. [2]
c.i.)Contrast the memory requirements of a laptop computer and a file server. [2]
c.ii.Contrast the processor speed requirements of a laptop computer and a file server.[2]
d.State two types of sensor that are required to control the lighting to ensure it switches on when it is required. [2]
e.Explain how the system makes use of the data it receives from the sensors to determine when to switch the lights on. [4]
f.Outline how the system will prevent the lights from being switched off too quickly when it thinks the room is unoccupied. [2]
▶️Answer/Explanation
Ans:
a.)
Virtual memory;
to enable the hard drive to act as primary memory if required;
Paging;
scheme by which a computer stores and retrieves data from secondary storage for use in main memory;
Multitasking;
to enable more than one application to run at the same time;
Scheduling (method by which work is assigned to resources that complete the work);
to determine which process will own CPU for execution while another process is on hold.;
Policies (ways to choose which activities to perform);
according to which decisions are made about which operations should be authorized/ which resources should be allocated;
Interrupt handling;
so that urgent tasks required by parts of the system may be executed;
Polling;
to sampling the status of an external device;
Mark as 2 and 2.
b.)
The virtualization of real devices;
such as the use of drive letters for partitions to represent a virtual hard drive;
Use of icons;
to represent peripherals/to access different drives;
c.i.)
The primary memory/secondary memory in a laptop will be less / smaller than would be found on a file server;
because it is a smaller device that is used by an individual, so doesn’t need to store / run so many programmes simultaneously;
c.ii.)
The processor of a file server would be faster/have more cores than that of a laptop;
as it has many more resources to manage/as it needs to keep track of many workstations/printers/peripherals;
d.)
Light sensor;
infra-red/motion sensor;
e.)
The sensors send data to the processor continuously;
The data received from the sensors is converted to digital (using an analogue to digital convertor);
The readings are compared to pre-set values in the controller/system;
If the light level is found to be below the pre-set value and a presence is detected (in the room);
A signal is sent to the actuator to turn on the lights;
f.)
A timer (set to 5 minutes);
If the light level is found to be below the pre-set value a timer is activated but the lights remain on;
When the timer reaches 5 minutes, the lights switch off (if no further presence is detected);