Layers: applications, operating system, firmware and hardware

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Quick Questions

Shade in the A or B circle for each question.

1. Which order lists the layers from the bottom (lowest) to the top?

A Applications, operating system, firmware, hardware

B Hardware, firmware, operating system, applications

2. A web browser is an application. Which layer does it run directly on?

A The hardware

B The operating system

3. Which statement is correct?

A Each layer uses the services of the layer below it

B Each layer uses the services of the layer above it

4. Which layer is at the very bottom of the stack?

A Hardware

B Firmware

5. Which layer sits directly between the hardware and the operating system?

A Firmware (including the bootloader)

B Application software

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1Applications -> Operating system -> Firmware -> Hardware		AFirmware: bootloader -> loads Operating system
2Hardware (bottom) Firmware Operating system Applications (top)		BA stack drawn from the bottom up: hardware is the base layer and applications are the top layer, which uses the services of all the layers below.
3The bootloader in the firmware runs on the hardware and then loads the operating system.		CApplications do not run directly on the hardware. They need the operating system, which needs the firmware, which needs the hardware, so every layer depends on the one below.
4A word processor asks the operating system to save a file, because applications use the services of the layer below.		DEach layer runs on the one below it, so a program such as a web browser depends on every layer beneath it, down to the physical hardware.
5Hardware Operating system Firmware Applications		EThe firmware and operating system are in the wrong order. The operating system runs on the firmware, so the firmware must sit between the hardware and the operating system.
6Applications run directly on the Hardware, so the Operating system is not needed.		FApplication -> Operating system: save file

Definitions

software stack

Fill in the Blanks

Complete each line of code by filling in the missing parts.

applications runs on ________________

operating system runs on ________

firmware runs on ________

layer 1: hardware layer 2: ________ layer 3: operating system

layer 3: operating system layer _: applications

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A [ Applications ]

B [ Operating system ]

C [ Utility software ]

D [ Hardware ]

Question 2

A User opens a web browser

B The browser runs on firmware

C The OS runs on the firmware

D Firmware runs on the hardware

Question 3

A The game needs to play sound

B The OS asks the game to help

C The OS uses a sound driver

D The driver controls hardware

Question 4

A stack ← []

B PUSH(stack, 'Hardware')

C PUSH(stack, 'Apps')

D PUSH(stack, 'OS')

E PUSH(stack, 'Apps')

Question 5

A 1 Applications

B 2 Firmware

C 3 Operating system

D 4 Applications

Answer Key

Layers: applications, operating system, firmware and hardware

Section A: Quick Questions

B — Hardware, firmware, operating system, applications

B — The operating system

A — Each layer uses the services of the layer below it

A — Hardware

A — Firmware (including the bootloader)

Section B: Match the Pairs

Applications -> Operating system -> Firmware -> Hardware → Each layer runs on the one below it, so a program such as a web browser depends on every layer beneath it, down to the physical hardware.

Hardware (bottom) Firmware Operating system Applications (top) → A stack drawn from the bottom up: hardware is the base layer and applications are the top layer, which uses the services of all the layers below.

The bootloader in the firmware runs on the hardware and then loads the operating system. → Firmware: bootloader -> loads Operating system

A word processor asks the operating system to save a file, because applications use the services of the layer below. → Application -> Operating system: save file

Hardware Operating system Firmware Applications → The firmware and operating system are in the wrong order. The operating system runs on the firmware, so the firmware must sit between the hardware and the operating system.

Applications run directly on the Hardware, so the Operating system is not needed. → Applications do not run directly on the hardware. They need the operating system, which needs the firmware, which needs the hardware, so every layer depends on the one below.

Section C: Definitions

software stack — The layers of a computer: applications run on the operating system, which runs on firmware, which runs on hardware. Each layer depends on the layer below it.

Section D: Fill in the Blanks

applications runs on operating system

operating system runs on firmware

firmware runs on hardware

layer 1: hardware
layer 2: firmware
layer 3: operating system

layer 3: operating system
layer 4: applications

Section E: Spot the Error

C — The third layer of the stack is firmware, which sits between the operating system and the hardware. Utility software is part of system software and is not a separate layer. It should be [ Firmware ].

B — An application runs on the operating system, not directly on the firmware. Line 2 should be: The browser runs on the OS.

B — The dependency goes the wrong way. An application uses the services of the OS below it, so the game asks the OS to help, not the other way round.

C — The stack is built from the bottom up: hardware, firmware, OS, then applications. Pushing Apps on line 3 puts it on top of the hardware before the firmware. Line 3 should push 'Firmware'.

A — The layers are numbered from the bottom up, so layer 1 is the hardware. Applications are the top layer, layer 4. Line 1 should be: 1 Hardware.