The start-up sequence of a computer

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Quick Questions

Shade in the A or B circle for each question.

1. What runs first when a computer is switched on?

A The bootloader, stored in firmware

B The web browser, stored in RAM

2. Which statement about RAM at power-on is correct?

A RAM already holds the operating system because it is non-volatile

B RAM is empty because it is volatile and loses its contents when power is off

3. What is the job of the bootloader?

A To load the operating system from storage into RAM

B To load the user's applications into the CPU's registers

4. Where is the operating system loaded from during the boot sequence?

A From RAM into secondary storage (e.g. an SSD)

B From secondary storage (e.g. an SSD) into RAM

5. Which order of the boot sequence is correct?

A Power on, bootloader runs, OS loaded into RAM, user opens applications

B Power on, user opens applications, bootloader runs, OS loaded into RAM

Match the Pairs

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

Left column		Right column
1boot sequence		AThe bootloader in firmware starts first and begins loading the OS from storage into RAM
2bootloader.run()		Bif OS_ready: open(app)
3RAM is empty at power-on, so the OS must be copied into it from storage		Cload(OS, storage, RAM)
4Applications can only be opened after the OS is loaded and ready		DThe application is opened before the OS has been loaded. The OS must be loaded into RAM first, then the application opened.
5power_on -> open(app) -> load(OS)		ERAM is empty at power-on and does not hold the OS. The bootloader in firmware runs first and loads the OS into RAM.
6power_on -> RAM holds OS -> bootloader		FThe ordered steps from power on: the bootloader runs, loads the OS into RAM, and the OS is then ready for applications

Definitions

boot sequence

Fill in the Blanks

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

powerOn() runBootloader(________) loadOS(storage, RAM)

powerOn() runBootloader(firmware) loadOS(_______, RAM)

powerOn() ramUsed ← _ runBootloader(firmware)

osReady ← TRUE IF _______ THEN openApplication("browser")

powerOn() runBootloader(firmware) ______(storage, RAM)

Spot the Error

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

Question 1

A POWER_ON

B RUN bootloader FROM firmware

C LOAD OS FROM storage TO RAM

D OS_READY = FALSE

E OPEN applications

Question 2

A POWER_ON

B RUN bootloader FROM RAM

C LOAD OS FROM storage TO RAM

Question 3

A POWER_ON

B RUN bootloader FROM firmware

C LOAD OS FROM RAM TO storage

D OPEN applications

Question 4

A POWER_ON

B RAM = FULL

C RUN bootloader

D LOAD OS INTO RAM

Question 5

A OPEN applications

B RUN bootloader FROM firmware

C LOAD OS FROM storage TO RAM

Answer Key

The start-up sequence of a computer

Section A: Quick Questions

A — The bootloader, stored in firmware

B — RAM is empty because it is volatile and loses its contents when power is off

A — To load the operating system from storage into RAM

B — From secondary storage (e.g. an SSD) into RAM

A — Power on, bootloader runs, OS loaded into RAM, user opens applications

Section B: Match the Pairs

boot sequence → The ordered steps from power on: the bootloader runs, loads the OS into RAM, and the OS is then ready for applications

bootloader.run() → The bootloader in firmware starts first and begins loading the OS from storage into RAM

RAM is empty at power-on, so the OS must be copied into it from storage → load(OS, storage, RAM)

Applications can only be opened after the OS is loaded and ready → if OS_ready: open(app)

power_on -> open(app) -> load(OS) → The application is opened before the OS has been loaded. The OS must be loaded into RAM first, then the application opened.

power_on -> RAM holds OS -> bootloader → RAM is empty at power-on and does not hold the OS. The bootloader in firmware runs first and loads the OS into RAM.

Section C: Definitions

boot sequence — Power on, the bootloader in firmware runs and loads the OS from storage into RAM (which is empty at power-on). Once the OS is ready, the user can open applications.

Section D: Fill in the Blanks

powerOn()
runBootloader(firmware)
loadOS(storage, RAM)

powerOn()
runBootloader(firmware)
loadOS(storage, RAM)

powerOn()
ramUsed ← 0
runBootloader(firmware)

osReady ← TRUE
IF osReady THEN
  openApplication("browser")

powerOn()
runBootloader(firmware)
loadOS(storage, RAM)

Section E: Spot the Error

D — Once the bootloader has loaded the OS into RAM, the OS is ready, so it should be OS_READY = TRUE. Only then can the user open applications.

B — RAM is empty at power-on, so the bootloader cannot run from it. It is stored in firmware and runs from there: RUN bootloader FROM firmware.

C — The direction is reversed. RAM is empty at power-on, so the bootloader copies the OS from storage into RAM: LOAD OS FROM storage TO RAM.

B — RAM is volatile and loses its contents when power is off, so it is empty at power-on. It should be RAM = EMPTY.

A — The start-up sequence begins with power on. Applications cannot be opened until the bootloader has loaded the OS, so line 1 should be POWER_ON.