Exam practice

The diagram should show:

• input devices (e.g. a keyboard, a touchscreen) with an arrow to the processor;
• the processor with an arrow to the output devices (e.g. a screen, a speaker);
• memory (RAM) joined to the processor with a two-way arrow;
• storage (e.g. an SSD, a hard disk) joined to memory with a two-way arrow: programs and files are loaded into memory, and saved back to storage.

(It can also note that all the parts are joined by the motherboard.)

A computer needs both because no one kind is fast, big, cheap and able to keep things all at once. The processor needs fast memory to work quickly, and you need storage to keep your work when the power is off. So programs and files live in storage and are loaded into memory to be used.

• i.Still there. It was saved in storage, which keeps its data without power.
• ii.Lost. The changes were only in memory, which forgets everything when the power goes.
• iii.Still there. The program is installed in storage; only the copy that was running in memory was lost, and it can be loaded again.

A UPS would have kept the computer on long enough to save; saving often would have kept most of the changes.

The clock speed is how many ticks the processor’s clock makes each second; at each tick the processor takes a small step. It is measured in hertz; 1 GHz is a thousand million ticks a second.
2.5 GHz = 2.5 × 1,000,000,000 = 2,500,000,000 ticks a second.
It can’t be called slower just from that, because processors of different designs do different amounts of work in each tick, and may have different numbers of cores. A newer design at 2.5 GHz can be faster than an older one at 3 GHz. Only processors of the same family compare fairly by GHz.

A core is one processing unit inside a processor chip, able to follow its own list of instructions. A processor with several cores can work on several jobs at the same moment.
More cores help when there are many jobs at once, or a job that can be split into parts done at the same time: several apps running, a video call while a file downloads, making a video smaller. They don’t help a job that must go step by step, each step needing the one before: that runs on one core, however many there are.

A hard disk drive keeps data as tiny magnetized spots on spinning metal platters, written and read by a head on a moving arm. Advantage: it holds a lot of data for little money.
A solid-state drive keeps data in flash memory chips, as electric charge trapped in tiny cells, with no moving parts. Advantage: it is much faster, silent, and tougher if bumped.

• i.HDMI (or USB-C with an adapter, on some laptops): it carries the picture and the sound to the TV.
• ii.USB-C: new phones charge through it, and it carries data as well.
• iii.The audio jack, 3.5 mm: it carries sound to the earphones.
• iv.Ethernet: it joins the computer to a network by a cable.

Any four:

• accelerometer: turns the picture when the phone is turned; counts steps.
• gyroscope: steadies videos; looking round 360° photos.
• proximity sensor: turns the screen off near your ear during a call.
• light sensor: changes the screen’s brightness to suit the room.
• magnetometer: the compass, and which way you face on a map.
• GPS receiver: shows where you are on a map.
• fingerprint reader: unlocks the phone for its owner.

Any four:

1. Starting up (booting): loads itself from storage into memory when you press the power button, and shows the home screen.
2. Sharing the processor (scheduling): gives the music app and the map app turns, so both run at once.
3. Managing memory: gives each app its own part of memory, and closes an app you left long ago when memory is full.
4. Keeping files: saves a new photo in storage and remembers where it is.
5. Working the hardware with drivers: lets the camera app use the camera, sends sound to earphones when they are plugged in.
6. Safety: asks “Allow this app to use your location?”, keeps the screen lock, installs security updates.

1. The touchscreen (input) senses your finger and where it touched.
2. The operating system works out which icon you tapped.
3. The operating system loads the app from storage into memory (RAM), first closing an app not used for a while if memory is full.
4. The processor carries out the app’s instructions from memory, taking turns with the other running apps.
5. The app asks the operating system for anything it needs, such as the screen; the operating system works the hardware through its drivers.
6. The app’s picture is shown on the screen (output).

Laptop 1 is the better choice for her:

• It is within the family’s budget (Rs 58,000); Laptop 2 is Rs 2,000 over.
• 8 GB of RAM and a recent mid-range processor are enough for typing, spreadsheets and learning to program; the extra speed and RAM of Laptop 2 would mostly go unused.
• Its battery lasts longer, about 8 hours, which matters at school and in power cuts.
• It is lighter to carry to school.
• It has HDMI and USB-A, so it plugs straight into a classroom projector and older pen drives without adapters.

(Laptop 2 would be the better choice for someone editing video or playing heavy games, who could pay more.)

• The environment: a phone with years of updates, a battery that can be replaced and repairs available lasts longer, so fewer phones are made and thrown away as e-waste.
• The people who make phones: phones need metals such as cobalt, and in some mines children have been found working; buying from makers who check where their metals come from puts pressure on the others.
• The people who use it: a phone shared by a whole family, or used by a grandparent or someone who can’t see well, needs a big screen, simple settings or good accessibility features more than the fastest processor.