Inside Our Devices

A computer follows instructions to work with information. Those instructions make up a program. Your tablet can play a song because a program tells it what to do.

Look for the job it does

A desktop, laptop, tablet, smartphone and game console are computers. A smart speaker is a computer too. It can take in your voice and play an answer. It does not need a keyboard or a large screen.

You use computers to send messages, enjoy movies and find information. You can also make drawings, stories and music. One tablet can do several jobs by running different programs. Other computers control things, such as traffic lights.

Is it digital?

A digital device stores and works with information as numbers. A digital camera keeps a picture as information it can use. A digital watch handles information about time. A bicycle, scissors and a wind-up toy are non-digital. Their parts do their jobs without handling information as numbers.

Electricity alone does not make something digital. A simple flashlight has a battery, a bulb and a switch. It lights up, but does not store or work on information. A digital thermometer does: it measures temperature and turns the reading into numbers on its screen.

Try sorting three objects: a tablet, a wooden spoon and a game console. First ask what each does. The tablet runs apps, so it is digital. The spoon does not handle information, so it is non-digital. The game console follows programs to run games, so it is digital.

Choose for the job and the place

Imagine writing a long report at a desk. A desktop's large screen and keyboard give you room to work. Now imagine taking photos around your classroom. A tablet is easier to carry from table to table. For a call on a bus, a smartphone fits in your pocket.

Start with what you need to do. Then think about where you will use the device. A large screen helps at a desk; a small size helps when you move around.

People make all these computers. Engineers design the parts. Factories put them together. Programmers write the instructions that make them useful. A computer's jobs depend on the programs people have written for it.

Some computers are hidden inside other machines. You may see buttons and lights without seeing the computer that controls them.

A computer with a main job

An embedded computer is built into a machine to control it. Washing machines, microwave ovens, cars and elevators have them. They often run one main program for a particular job. Most washing machines cannot download a game as your tablet can.

Follow a microwave oven set for 30 seconds:

1. You choose the time and press Start.
2. Its computer starts the heating and turning plate.
3. It counts down and shows the time left.
4. At zero, it stops the heating and beeps.

The computer and the machine it controls form a control system. Some control systems use measurements. A thermostat measures how warm a room is. With a setting of 68 °F (20 °C), it turns the heater on when the room is colder. It turns the heater off when the room is warm enough.

Robots sense and act

A robot is a computer-controlled machine that can sense things and act. Often it works without a person guiding every step. A robot vacuum senses walls and stairs. Its program uses those readings to change direction.

Real robots come in many shapes. A factory robot may be an arm fixed to the floor. It can build or paint cars. Warehouse robots carry shelves, and robot lawn mowers cut grass. Some robots help doctors during operations. Robotic rovers explore Mars.

A robot does not need a face, legs or a voice. Robots in movies may seem to feel happy or sad. Real robots follow their programs and do not have feelings.

Hidden computers can connect

Some everyday machines also connect to the internet. These are smart devices. A smart doorbell can send video to a phone. A smart light can receive a command from a tablet. Everyday connected things form the Internet of Things.

Look at a ticket machine: you choose a journey, and it prints a ticket. The computer inside uses your choice to control the result. At a crosswalk, a button press goes into a system that controls lights. You can spot a hidden computer by noticing the information it takes in and the machine it controls.

Touch a tablet's screen, then open a drawing app. The screen and the app work together, but they are different kinds of things.

Hardware is the physical stuff

Hardware means the parts you can touch. A screen, mouse, keyboard, printer and speakers are hardware. So are the chips and other parts inside a case. A soft rubber cover or bendy cable is still hardware. The word does not mean that every part feels hard.

Software means programs: the instructions that tell hardware what to do. Drawing apps, games, web browsers and word processors are software. You can touch the screen showing a game. You cannot touch the game's instructions themselves.

A downloaded game is software. The drive or card holding it is hardware. Keeping a program on a physical part does not turn the program into hardware.

Follow a colored line

Suppose you choose blue in a drawing app. You slide your finger across the tablet. The touch screen detects where your finger moves. The app's instructions tell the computer to make a blue line there. The screen then shows the line.

The physical screen needs instructions to do this job. The app needs physical parts to run on. Hardware and software together form a computer system.

Two kinds of software

An app, short for application, does a job for you. You might open an app to write, draw, play music or calculate.

System software looks after the computer itself. The operating system is the main example. It starts when you turn the device on. It shows the home screen, opens and closes apps, and looks after files. It also manages connected parts such as a printer.

Think about opening a music app. The operating system helps open it and manages the device. The music app does your chosen job: playing a song.

Software can change

An update is a newer version of software. It can fix mistakes, add features or make the device safer. Installing an update changes instructions; it does not replace the screen or keyboard.

These words also help describe problems. A cracked screen is damaged hardware. An app that keeps closing has a software problem. Naming the part or program gives you a clearer starting point when something goes wrong.

Computer parts can sit separately on a desk or share one case. Learning their names helps you explain what you need.

A computer on a desk

A monitor is a screen that shows words and pictures. A keyboard lets you type. A mouse lets you point and click. Speakers play sound. Many desktops also have a separate case, or tower, holding the main working parts.

On that kind of desktop, turning off the monitor only stops the display. The computer in the separate case keeps running. An all-in-one desktop is different: its main parts are built into the screen unit.

A laptop puts many parts into one folding case. It has a screen, keyboard, speakers, microphone, camera and battery. Its trackpad, also called a touchpad, lets you move the pointer with your finger. Tablets and phones use a touch screen to show things and detect touches.

Add a part for a job

Extra parts connected to a computer are peripherals. A printer makes a paper copy. A webcam takes video. A headset has headphones and a microphone. A USB flash drive carries files between computers.

For an online lesson, match each part to its job. The camera takes your picture. The microphone picks up your voice. Speakers let you hear the teacher. The screen shows the lesson. A headset lets you speak and listen through one connected item.

A port is a socket for a cable. You may see a USB port or a headphone jack. A charger gives energy to the battery. Use the words that match your action: click a mouse, tap or swipe a touch screen, and slide a finger on a trackpad.

Make a device easier to use

An icon is a small picture that stands for an app or action. A camera picture can open the camera. A speaker picture can help you find the sound controls.

People see, hear and move in different ways. Designers build features to help:

• Bigger text makes words easier to see.
• A screen reader reads screen words aloud.
• Captions show spoken words as text.
• Voice control lets you speak commands.

For example, captions let you read what someone says when you cannot hear the sound. Voice control can help when using a keyboard is difficult. Choosing a helpful feature is part of choosing the right way to use a device.

A computer needs information to work on. Sometimes you give it that information yourself. Sometimes a device collects it for you.

Follow the direction

Input is information or instructions going into a computer. An input device is hardware that puts them in. A keyboard sends letters and numbers. A mouse or trackpad sends pointing and clicking. A touch screen detects taps and swipes.

Other input devices collect different things. A microphone takes in sound. A camera takes in pictures and video. A scanner makes a digital copy of a page. A game controller sends button presses. Input can be a voice, picture or position, as well as typed words.

You act, or a sensor acts

Manual input happens when a person gives information by doing something. Typing, clicking, tapping and speaking commands are examples.

Automatic input is collected without someone giving each reading. A sensor measures something around it. A light sensor measures brightness. A temperature sensor measures hot and cold. A motion sensor notices movement. Sound sensors measure loudness, and distance sensors measure how far away something is.

A camera can work in either way. Press its photo button, and you give manual input. A doorbell camera can start by itself when a motion sensor notices a visitor. That recording starts with automatic input. Ask how the information was collected, not just what the device is called.

Keep readings over time

A data logger uses sensors to measure and save readings at regular times. Your class can leave one outside and look at the readings later. Nobody needs to stand beside it all day.

Suppose it records temperature every hour from 8:00 a.m. to 2:00 p.m., including both times. Count each reading:

1. The morning readings are at 8, 9, 10 and 11.
2. There is a reading at noon.
3. The afternoon readings are at 1 and 2.

That gives seven readings. There are six hour-long gaps between the start and finish. The number of gaps is smaller because the logger also takes a reading at the start.

You can see, hear or feel a computer's results. Some results even make a machine move.

Match the result to the part

Output is a result coming out after the computer works on information. An output device is the hardware that gives the result.

A monitor shows words, pictures and video. Speakers and headphones play sounds. A printer puts words and pictures on paper. A projector makes a large picture on a wall or board.

Choose the part that fits your need. A printer gives you a paper page to hand in. A projector helps the whole class see one picture. Headphones let you listen without playing sound into the room.

Output can make things happen

A motor can turn a robot's wheels or slide a door open. This is output too. An actuator is an output device that makes something move or happen. A small light can show that a battery is charging. A buzzer can announce that a microwave has finished. A phone's vibration is output you feel.

A 3D printer builds a real object in layers, often using melted plastic. Its output is the object it builds. A paper printer and a 3D printer give very different results, but both give output.

One device can do both jobs

A touch screen detects your taps: that is input. The same screen shows pictures: that is output. A headset also does both. Its microphone takes your voice in, while its headphones play sound out.

Sound alone does not tell you the direction. A microphone and a speaker both deal with sound. The microphone takes it into the computer; the speaker gives it out. A camera takes pictures in, while a screen shows pictures out.

Follow a game action. You press the space bar. The keyboard sends the press into the computer. The game works out what should happen. The screen shows a jump, and the speakers play a sound. One input has led to two kinds of output.

To sort a part, name what it is doing at that moment. Is the information traveling into the computer, or is a result coming out? With a headset, naming the microphone or headphones makes the direction clear.

Pressing a button and seeing a result can seem instant. Between them, the computer works on the information.

Input, process, output

The input–process–output model, or IPO, helps you explain a system. Ask three questions: What goes in? What happens to it? What comes out?

Processing means working on the input by following a program. A computer might calculate an answer, compare two values or change a picture. Name the action, not just the machine doing it.

For a calculator adding 7 and 5:

1. Input: you press 7, +, 5 and =.
2. Process: the calculator adds the two numbers.
3. Output: its display shows 12.

The calculator is the whole device. Calling the device itself the process misses the action: adding.

Try a different kind of result

An automatic door begins with a sensor noticing someone nearby. Its program checks the input and decides to open. A motor slides the door. The sensor gives input; checking and deciding are processing; the movement is output. After no movement is detected for a few seconds, the program tells the motor to close the door.

Typing works through the same three steps. Press the A key with Caps Lock off. The computer works out which key you pressed and where the letter belongs. A small "a" appears on the screen. Hold Shift as you press the key to get a capital "A".

Printing also needs processing. Clicking Print gives input. The computer turns your page into instructions for the printer. The printed page is output. When recording your voice, a microphone takes sound in. The computer turns it into information it can save. Playing the recording through a speaker gives output.

The model works with simple tools too

A hand-held pencil sharpener has input, process and output. The input is a blunt pencil and your turning hand. The blade shaves off wood. The output is a sharp pencil and shavings. This tool is non-digital: moving parts do the work. A digital system handles information as numbers.

People design systems and write their programs. People also choose inputs and use results. If you enter 7 + 6 when you meant 7 + 5, a working calculator shows 13. It followed the input it received. Checking the input helps you understand an unexpected output.

Inside a computer, a small chip carries out the program's instructions. It is called the processor, or CPU. CPU stands for central processing unit.

Work happens in small steps

The processor does the working-out part of input, process and output. It follows small instructions very quickly. A modern processor can carry out billions of simple steps each second. That speed lets a game change its picture many times each second.

The work can include different actions:

• Calculate: add points to a game score.
• Compare: check whether a room is colder than 68 °F (20 °C).
• Follow a rule: add one point when a player touches a coin.

A rule tells the processor what action to take. The processor carries it out; it does not choose its own goal.

Think of a recipe

Imagine a cook following a recipe. The recipe gives the instructions, the ingredients go in, and a meal comes out. This helps you picture a program, input and output. The processor's job is like carrying out the recipe's steps.

People sometimes call the processor a computer's "brain." It does the working out, but it does not think or understand as you do. It carries out programmed instructions. Calling it a brain should not make you imagine that it has ideas or feelings.

Hidden computers need processors too

The computer in a microwave oven has a processor. It carries out timing and control instructions. A smartphone has a processor that runs its apps. A big screen is not what makes processing happen; the working chip can be hidden inside a small device.

The processor needs electricity and gets warm while working. Many desktops and laptops have fans and air vents to let heat escape. The processor works on information, while memory and storage hold it. Your saved photos are kept in storage; the processor uses information when an app needs to work on them.

Your computer holds information in two different ways. Memory, also called RAM, holds what it is using now. Storage keeps programs and saved files for later.

Your desk and bookshelf

Think of memory as the top of your desk. You spread out the work you need right now. Think of storage as a bookshelf. You keep things there until you need them again.

When you open a saved story, the computer copies it from storage into memory. The processor reads and changes the information in memory quickly. Press Save, and your changes are copied into storage.

Memory loses its contents when the power goes off. Storage keeps saved files when power is off. A story on your screen may contain changes that have not yet reached storage.

What survives a flat battery?

You write for 20 minutes. You save after 15 minutes, then keep writing. The app does not save again before the battery runs out.

1. The first 15 minutes of work reached storage.
2. The last changes were in memory only.
3. The difference is five minutes: $20-15=5$.

When you turn the laptop on again, the saved story is still there. The last five minutes of changes are lost. Some apps save by themselves. Saving your work yourself makes sure your changes are kept.

Space for different jobs

Memory is usually smaller than storage, but it is faster. A laptop might have 8 gigabytes of memory and 256 gigabytes of storage. A gigabyte measures an amount of information. That laptop has 32 times as much storage as memory: $256÷8=32$.

Too many open apps can make a device slow because they need working memory. Full storage causes a different problem: there is no room to save new photos or files. People sometimes say a phone has "128 gigabytes of memory" when they mean its storage. Ask whether they mean working space now or saved space for later.

Restarting clears working memory

A restart switches the device off and on. It clears memory and starts programs again, which can help a stuck app. It does not delete files already saved in storage. Unsaved changes can be lost, so save before restarting when you can.

A file is information kept under a name. It might be a story, photo, song, video, game or app. Keeping it in storage lets you retrieve it: find and open it later.

Recognize the type

A file's type tells you what kind of information it holds. Text files hold words, image files hold pictures, and audio files hold sounds. Video files hold moving pictures and often sound. Program files hold instructions.

The ending after a dot is a file extension. It usually gives a clue to the type:

• "mystory.txt" and "mystory.docx" are text documents.
• "beach.jpg" and "beach.png" are images.
• "song.mp3" is audio.
• "party.mp4" is video.

Changing the ending does not change the contents. Rename "cat.jpg" as "cat.mp3", and it is still a picture. A music app cannot play the picture as a song.

Compare file sizes

File size tells you how much storage a file uses. Sizes are measured in bytes. Larger units are kilobytes (KB), megabytes (MB) and gigabytes (GB). One MB is about 1,000 KB. One GB is about 1,000 MB.

A short plain-text story can use only a few KB. Photos and songs often use a few MB. A minute of video may use tens of MB or more. Big games can use many GB. These are useful guides; actual files have their own sizes.

A tablet has 600 MB free. Each photo uses about 3 MB. Divide the free space by each photo's size: $600÷3=200$. About 200 photos fit. A 150 MB video uses the same space as 50 of those photos: $150÷3=50$.

Choose where to keep a file

A hard disk drive uses spinning disks. Solid-state storage uses chips with no moving parts. Most new laptops, tablets and phones have solid-state storage inside.

A USB flash drive is easy to carry between computers. A memory card can hold camera photos. CDs and DVDs are discs read by a laser. Each storage device has a capacity, meaning the most it can hold. Full storage has no room for another file until files are moved or removed.

Cloud storage keeps files on other computers called servers. You reach them through the internet and can use different devices. If you need a file offline, keep a copy on your device too.

A computer system does a task by making its parts work together. You can follow the information through input, memory, processor, output and storage.

Follow a calculation

Open a calculator app and enter 8 × 3:

1. Input: you tap 8, ×, 3 and =.
2. Memory: the working information includes 8, 3 and "multiply."
3. Processor: it follows the app's instructions and calculates 24.
4. Output: the screen shows 24.

The touch screen has two jobs here. It detects taps for input and shows the answer for output. The app is software; the screen, processor and memory are hardware.

For a drawing, your finger's movement is input. The drawing app works in memory. The processor turns the touch into a colored line. The screen displays it. Saving puts the picture into storage as an image file. Showing a picture now and keeping it for tomorrow are different jobs.

Draw the main path as Input → Process → Output. Memory helps hold current information during processing. Add Storage beside the process with arrows in both directions. One arrow shows saving; the other shows loading saved information again.

Work with or without the internet

Online means connected to the internet. Offline means not connected. A calculator or drawing app can work offline. A live video call and a web search need an internet connection.

Devices can send information out to other devices and receive information from them. What one computer sends becomes input for the receiving computer. Think of an online form. You type your name. Your device sends it to another computer, which processes and stores it. A reply such as "Thank you!" returns and appears on your screen.

Two devices share a call

Your camera and microphone take in your face and voice. Your device processes and sends that information. Your friend's device receives it, shows your face and plays your voice. Information also travels back the other way so you can see and hear your friend.

Everyday connected things form the Internet of Things. A garden weather sensor can measure and send readings without moving anything. A smart light can receive a command and switch on without measuring the weather. A smart doorbell senses a visitor, processes information and sends video to a phone. These things can have sensors, actuators, or both.

A device lasts better when you handle it carefully. Looking after your work also means caring for software and saved files.

Carry, place and clean

Use two hands to carry a tablet or a closed laptop. A case or cover helps protect it while you move. Put devices on a flat table, away from the edge. Lifting a laptop by its open screen can damage it.

Keep food and drinks away. Crumbs can jam keys, and spilled drinks can harm the parts inside. Avoid water, strong heat and strong cold. A hot car or sunny window is a poor place to leave a device. Keep laptop air vents clear so heat can escape.

Switch a device off before cleaning its screen gently with a soft, dry cloth. Ask an adult before using cleaning liquid. Use your finger or the proper tool for a touch screen, not a pen or scissors.

Use electricity safely

Keep hands dry around plugs, cables and outlets. Hold the plug itself when unplugging; pulling the cable can damage it. Keep cables tidy so nobody trips. Use the charger that belongs to the device. If a device gets very hot, smells of burning, has a swollen battery or a cracked screen, stop using it, leave it closed and tell an adult right away.

When you finish, close apps and follow your school's shutdown or sleep routine. Return the device to its charging place so it is ready for the next person.

Protect the work inside

An update can fix software mistakes and close security gaps. Install it when an adult says it is OK.

A backup is a second copy of an important file in another place. Cloud storage or a USB flash drive can hold it. Saving on the device keeps your current work, but a backup helps if that device stops working.

Mia backs up her drawing project to cloud storage. A week later, her tablet falls into a puddle and stops working. She can open the backup on another device. Changes made after that backup are missing from that copy. A backup only keeps the version copied at that time.

A device lock uses a password or PIN to stop someone opening your device without permission. Keep that code to yourself instead of sharing it with friends. A lock helps control access; a backup helps recover files. They protect your work in different ways.

When something goes wrong, start by noticing exactly what happens. Troubleshooting means finding and fixing a problem step by step.

Describe what you notice

"It's broken" gives a helper very little information. Try, "When I press Play, the video moves but has no sound." Say what you expected, what happened instead and when it started.

Then follow a simple plan:

1. Say exactly what is wrong.
2. Check the simple things.
3. Try one fix.
4. Test whether it worked.
5. If simple fixes fail, ask for help and explain what you tried.

The useful check depends on the problem. Look for power, battery charge, firmly connected cables, sound volume and mute. Check the internet connection when the task needs it.

Work through a sound problem

A video plays silently. You check the volume and find it at zero. Turn it up, then play the video again. It is still silent.

Next you notice headphones plugged in. Sound is going to them. Unplug the headphones and test again. Now sound comes from the speakers. Because you tested after each change, you know which change made the speakers play.

Changing three settings at once can hide the cause. You might also change something that was already right. One change and one test keep the steps clear.

When an app stops responding

An app that freezes may be busy. Wait a few seconds. If it stays stuck, close it and open it again. If that fails, restart the device. Save work first if you can. A restart clears memory and starts programs again; unsaved changes can be lost.

A loose cable or flat battery is a hardware problem. An app that freezes or closes by itself points to software. These words help you choose a sensible first check, though a helper may need to investigate further.

Give a helper useful information

If simple checks do not work, ask an adult or the school's technology helper. You might say, "The drawing app stops when I choose a brush. I waited, reopened it and tested again. It still stops."

Banging a device, pressing lots of buttons or deleting unfamiliar files can make matters worse.