Fixing Problems and Learning Any New Tool

Troubleshooting is finding the cause of a problem with a computer, a phone or any machine, and fixing it, step by step. You met its cousin in Grade 6: debugging, finding the mistakes in a program Grade 6: Bugs and debugging. Troubleshooting uses the same habits on everything else: the Wi-Fi, a printer, an app that crashes, a laptop that won’t start.

Most people troubleshoot by guessing: they press things at random, change five settings at once, and give up. A method is faster, and it works even on a machine you have never seen before. Figure 6.1 shows it.

1. Say exactly what is wrong

“The internet isn’t working” could mean a hundred things. Before touching anything, answer four questions:

• What did you expect, and what happened instead? “I expected the results page to open. Instead the browser says This site can’t be reached.”
• Exactly where? One website or all of them? One app, or the whole phone? Only on the laptop, or on the phone too?
• Since when? Always, since this morning, or only sometimes?
• What changed just before? An update, a new app, a power cut, a moved cable, a new password, a phone that fell. A problem that started right after a change is very often caused by it.

Writing the answers down already halves the work, and if you need help later, the person helping needs exactly these answers.

2. Try a restart

It is a joke that every computer expert says “have you tried switching it off and on again?”, but it is good advice, and it helps to know why.

In Grade 7 you saw that memory (RAM) holds whatever is running now, and that it is cleared when the power goes off Grade 7: Memory and storage. A program that has run for days can get itself into a bad state: a job stuck waiting for something that will never come, memory slowly filled and never given back, a setting changed halfway. Restarting throws all of that away. Everything loads fresh from storage, in a clean state, the way it was tested by the people who made it.

So restarts fix a great many problems, in phones, laptops, Wi-Fi routers, printers and smart TVs. Do it properly:

• Save your work first. A restart empties memory, and with it anything not saved.
• Really restart. Locking a phone or closing a laptop’s lid only puts it to sleep, and memory stays as it was. Use Restart, or switch it off fully and on again.
• A router or a modem: switch it off at the socket, wait half a minute, switch it on, and give it a couple of minutes to connect before you test. Its lights show when it is ready.

When something fails, a computer usually says why. An error message is a message from a program saying that something went wrong, and very often what. Most people close it without reading it. That throws away the best clue there is.

Read the whole message, slowly. Most error messages have some of these parts:

• What failed: “Couldn’t save the file”, “This site can’t be reached”.
• Why, if the program knows: “The disk is full”, “The file is open in another program”, “No internet connection”.
• An error code: a number or a short name, such as 404 or 0x80070070, which means one exact thing to the program that showed it. It looks like nonsense, but it is the most useful part to search for.
• Where, for programs: the file and the line, as in Python’s tracebacks.

Here are messages you will meet, and what they are really telling you:

In Grade 8 you learned to read Python’s error messages from the bottom up: the last line names the kind of error, and the lines above say where it happened Grade 8: Reading error messages. The same habit works for every program: find the line that says what kind of thing went wrong, and the part that says where.

Most problems happen somewhere along a chain of parts that must all work. To open a website on a laptop at home, the browser must work, the laptop must be connected to the Wi-Fi, the router must pass the data on, the fiber line must carry it out of the house, and the website itself must be answering. If any one part fails, the website doesn’t open, and the screen looks the same whichever part it was.

So the next step is to isolate the problem: find out which part has failed, by tests that each rule out some parts. Three kinds of test do most of the work:

• Swap one part. Try another website, another browser, another charger, another cable, another account. If it works with the other one, the first one is the problem.
• Try it from somewhere else. Does the website open on a phone? On the same Wi-Fi, or only on mobile data? Does your friend’s phone charge from your charger?
• Look at what each part shows. The router’s lights, the Wi-Fi icon, a printer’s little screen. Parts often tell you they are unhappy.

A good test splits what is still possible into two groups, so that either result rules out a lot. You met this idea in Grade 8 as binary search: look in the middle, and throw away half each time Grade 8: Binary search. Testing websites on a phone that uses the home Wi-Fi is like that: if they open, the router and the line are working, so the problem is in the laptop or the one website; if nothing opens, it is in the router or the line.

Whatever problem you have, someone else has almost certainly had it before, and many of them wrote about it: on the program maker’s help pages, in forums, on question-and-answer websites. The trick is to search with the words they would have used. In Grade 7 you learned to choose search words and use operators Grade 7: Search operators. For an error:

1. Copy the exact message, or its most important line, and put it in quotes, so the search engine looks for those words together.
2. Add the program’s name, and the device or operating system. The same words can mean different things in different programs.
3. Leave out what is only yours: your file names and folders, your name, line numbers in your own program, dates and times. Nobody else has them, so they only hide the pages that would help. Never put a password, a phone number or a code into a search.
4. Read the dates and versions in what you find. Programs change. An answer from many versions ago may describe menus that no longer exist.
5. Read more than one answer, and prefer the program maker’s own help pages, and answers that others say worked, over a single stranger’s guess.

Asking for help well

When you are stuck after a few honest tries, ask: a teacher, a friend who knows the program, the program’s forum. People help most when the question is easy to answer, so give them what they need:

• what you were trying to do, and what you expected;
• what happened instead, with the exact error message (copied, or a screenshot with your personal details covered);
• what you have already tried, and what each try did;
• the device, the operating system and the program’s version.

Compare “my laptop internet not working plz help” with: “Since this morning my laptop connects to the home Wi-Fi but no website opens; the browser says This site can’t be reached. My phone on the same Wi-Fi works. I restarted the laptop and the router; no change.” The second can be answered in a minute. Often, writing it makes you see the answer yourself.

Two problems come up again and again: a phone that has become slow, and a disk with no space left. Each has a handful of usual causes, and the method finds which one it is.

Why a phone gets slow

In Grade 8 you freed space on a full phone Grade 8: Storage full. A slow phone can have that cause, or others:

• Too little memory for what you use. Each open app takes part of the RAM. When it runs out, the phone closes apps to make room and loads them again when you return, which is slow. Heavy apps (games, video editors, some social media apps) take far more than light ones.
• Storage almost full. The system needs free space to work: for temporary files, for updates, and to manage its flash memory. With almost none left, everything slows down.
• Something busy in the background. An app stuck in a loop, many apps syncing at once, or malware working secretly. The battery settings, which list what has used the battery, show it: an app you hardly opened near the top of the list is a clue.
• Heat. A hot phone slows its processor on purpose, to protect itself.
• A worn battery. An old battery can’t always give the power the processor needs at its busiest, so some phones slow down rather than switch off.
• Age. Each year’s apps and system updates expect a little more power. A phone that was fast five years ago is slow with today’s apps, and nothing is broken.

So the method again: say exactly when it is slow (always? only in one app? only when hot? only since an update?), restart, look at storage, battery use and battery health, and change one thing at a time.

A full disk on a computer

A laptop or a lab computer with a full disk can’t save files or install updates, and it slows down for the same reasons as a phone. Don’t start deleting at random. Look first for what is big:

• The computer’s storage settings show what kinds of files take the space.
• In any folder, sort the files by size, biggest first (you will do this on the command line soon).
• The usual culprits: Downloads (installers and videos downloaded once and forgotten), videos anywhere, the Recycle Bin or Trash (deleted files still take space until it is emptied), temporary files, and copies of the same files in several places.

Then free space the safe way, as on a phone: empty the bin, remove what can come back (installers, temporary files), uninstall programs nobody uses, and move what you keep to a disk or the cloud, deleting the original only after checking that the copy opens.

In Grade 8 you installed apps on a phone only from its app store Grade 8: Installing apps only from safe places. On a computer there are more ways to get a program, and more traps. In Grade 7 you saw that malware gets in mostly through programs people install themselves Grade 7: How malware gets in. So get every program from its source, the people who make it:

• The computer’s own app store, where there is one: programs there are checked before they are listed.
• The maker’s own website. Type the address yourself, or follow the official link from the program’s Wikipedia article. Don’t trust the first search result: scammers buy adverts with famous programs’ names.
• A package manager: a program that installs other programs from a list its makers check, used by typing a command. Linux computers get almost all their software this way.

Never install from “free download” sites full of buttons, from pop-ups, from a link in a chat, or a cracked copy of a paid program (one changed by a stranger to get round its license). Changing a program is exactly how malware is put in, and the person who cracked it gave it to you free for a reason.

While installing:

• Read who made it. When an installer asks for permission to make changes to the computer, the box names the publisher, the company or project that signed it with a digital signature (Grade 9, Digital signatures). “Unknown publisher” on a well-known program is a warning.
• Give administrator permission only to what you trust. An administrator can change anything on the computer, for every user. A real installer needs it, to put the program where every user can run it; that is exactly why a harmful one asks for it too.
• Choose the custom install, and untick extras: toolbars, “recommended” programs, a change of your browser’s home page.

Checking that the file is the real one

Some makers publish a checksum beside each download: the file’s hash, a long string of letters and numbers worked out from every bit of the file. In Grade 9 you saw that changing even one bit of a file gives a completely different hash Grade 9: Hashes keep things correct, too. So you can work out the hash of the file you downloaded and compare it with the one on the maker’s website. If they are the same, your file is exactly the file the maker published, not damaged on the way or swapped for another. If they differ in even one character, don’t install it.

Everything you do on a computer by tapping and clicking can also be done by typing. A command line is a window where you type commands, one line at a time, and the computer types back its answer. The window is called a terminal, and the program in it that reads your commands and runs them is called a shell.

Why learn it, when you can click?

• Every programmer and every server uses it. The computers that run websites and the cloud (Unit 5) usually have no screen at all: people type commands to them from far away.
• It is exact and repeatable. A command can be written down, sent to a friend or kept in your notes, and it does exactly the same thing every time. “Click the third icon in the second menu” doesn’t survive a new version.
• Many tools have no buttons at all, only commands, and so do many fixes you will find when you search an error.
• It answers in words you can read and search, as you will see.
• In Grade 11 you will write programs that do hours of work at one command.

Figure 6.3 shows a line in a terminal. Before the $ is the prompt: the shell telling you who you are, which computer you are on and which folder you are in, and that it is your turn to type. After it, you type a command (the program to run) and often an argument (what it should work on). Press Enter, and the output, what the command printed, appears on the next lines.

Folders and where you are

In Grade 6 you saw that folders make a tree, each folder inside another Grade 6: A tree of folders. On a command line you are always in one folder of that tree, called the working directory (directory is another word for folder). Commands work there unless you say otherwise.

A path is the way to a folder or file through the tree, with its folders’ names joined by /:

• /home/asha/school is an absolute path: it starts at the very top of the tree, /, called the root, and works from anywhere.
• school/class10 is a relative path: it starts from the folder you are in.
• ~ means your home folder, .. means the folder one level up, and . means the folder you are in.

The first commands to know:

Commands, folders and file names are case-sensitive: ls works and Ls doesn’t, and Photos is a different folder from photos.

Running a program and reading its output

To run a Python program from the command line, type python3 and the program’s file name as its argument. Whatever the program prints appears in the terminal, and so does any error.

On the way you met one error, and there is a second you will meet sooner or later. Together they teach the most important thing about running programs:

asha@lab-pc:~$ python3 results.pypython3: can't open file '/home/asha/results.py': [Errno 2] No such file or directory

Here Python couldn’t find the program: there is no results.py in the folder she was in. Read the path in the message: Python looked for /home/asha/results.py, so the fix is to go where the file is. Now suppose she runs it from her home folder by giving its path:

asha@lab-pc:~$ python3 school/class10/results.pyTraceback (most recent call last):  File "/home/asha/school/class10/results.py", line 3, in <module>    with open("marks.csv") as f:         ~~~~^^^^^^^^^^^^^FileNotFoundError: [Errno 2] No such file or directory: 'marks.csv'

This time Python found the program and started it, but the program couldn’t find marks.csv. The program opens "marks.csv" with no folder in front, so it looks in the working directory, the folder you ran it from, not the folder the program is in. From ~/school/class10, where marks.csv is, it works:

asha@lab-pc:~/school/class10$ python3 results.pyStudents: 10Average mark: 74.5Highest: Rojina 96Below 50: ['Sujan']

Two messages that look alike, No such file or directory, came from different programs (Python itself, then results.py) about different files. Reading which program speaks, and which file it names, tells you what to fix.

Other messages you will meet, all from the shell itself:

Every year brings new programs, new apps and new kinds of tools that didn’t exist when your teachers were at school, and some that don’t exist yet as you read this. Nobody can teach you all of them. What you can learn is how to learn one, and that skill moves with you from tool to tool.

The ideas carry over

Most programs share the same ideas, so each new one is easier than the last. Look for them in anything new:

• Files: open, save, save as (a copy with a new name), export (save in another format, such as a PDF).
• Undo (Ctrl + Z): try things freely, because you can go back.
• Select, then act: choose the thing first, then what to do to it.
• Menus, settings, and a search for commands: many programs let you type what you want (“insert table”) instead of hunting through menus.
• Help: a Help menu, the F1 key, a ? icon, or --help after a command.
• Shortcuts: shown beside each menu item, learned a few at a time.

A photo editor’s layers, a spreadsheet’s formulas, a video editor’s timeline: each kind of program also has two or three ideas of its own. Find out what they are, and the buttons make sense.

A way to learn any program

1. Start with a small, real task. “Learn the photo editor” is too big. “Take the background out of this photo of our science fair poster” is a task you can finish, and you will know when it is done.
2. Read the built-in help and the official getting-started guide. The makers wrote it for the version you have. You learned to read documentation in Unit 1 Grade 10: Reading documentation.
3. Follow a tutorial, doing it as you go. A written tutorial or a video, but pause it and do each step on the real program. Watching someone else do it feels like learning, and isn’t. Check its date and version: an old tutorial shows old menus.
4. Ask an AI assistant, and treat its answer as a suggestion to test (below).
5. Practice on a copy. Work on a copy of the file, so a mistake costs nothing.
6. Check what you learned: do the task again, a few days later, without the tutorial. Then explain it to someone else. If you can teach it, you know it.

Learning with an AI assistant, and checking it

An AI assistant is a quick teacher: it explains, gives the steps, answers your follow-up questions in your own words, and doesn’t mind being asked the same thing five times. In Grade 8 you saw that it can also be confidently wrong Grade 8: Checking what it tells you, and in Unit 7 you will see exactly why. When you are learning a program, it gets things wrong in particular ways:

• it describes menus and buttons that don’t exist, or that were in an older version;
• it mixes up two similar programs, or the phone and the computer version of one;
• it invents options for commands that sound right but were never there.

So ask well, and then check: tell it the program, its version and your device, and ask for steps. Then try each step yourself, on a copy. A program is the perfect place to check an AI: if the menu isn’t there or the command gives an error, you know at once. When something it said turns out wrong, say so and ask again, or go to the official help.

The first answer was invented: there is no --biggest, and ls said so, in a message you now know how to read. The second was right, and you didn’t have to take its word for it: ls -lhS showed every size, biggest first. Checking took ten seconds.

This project has two parts. Part A needs a school computer lab and your teacher’s permission. Part B can be done with any program on any device, a phone too.