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Phase 0 · 1 / 6What a computer actually does
Phase 0Getting started
6 topics · 1–2 wks
  1. 1What a computer actually does
  2. 2Files, folders and paths
  3. 3The terminal, step by step
  4. 4Set up VS Code and Node
  5. 5Git and GitHub basics
  6. 6Using AI as a study partner
JourneyPhase 0What a computer actually does
01 / 08Overview

What a computer actually does

You'll learn the four jobs every computer does, and why a program must be a list of exact steps.

Why it mattersEvery line of code you write later is an instruction for this machine. Knowing what it can do makes code less mysterious.
about 45 min
02 / 08

Watch & read

Start with the required ones. The others are there when you need them.

Video
How Computers Work: What makes a computer, a computer?Code.org · YouTube · 5 min · English
MMamun's noteWatch all of it. Five minutes, and it names the four jobs from this page.
Video
How Computers Work: CPU, memory, input and outputCode.org · YouTube · 5 min · English
MMamun's noteWatch all of it. Pause when they talk about memory and think of the desk and the cupboard.
Video
CS50x 2024, Lecture 0: algorithms and pseudocodeCS50 (Harvard) · YouTube · 14 min · English
MMamun's noteWatch 51:30 to 1:05:10 only, the phone book part. It shows why every step must be exact. You can skip the rest of the lecture for now.
VideoOptional
Memory and storage: Crash Course Computer Science #19Crash Course · YouTube · 12 min · English
MMamun's noteOnly if you are curious. It is fast and goes into history and hardware. You do not need the details to move on.
03 / 08

Explanation

You use a computer every day. But what is it actually doing when you tap, type or click?

Every computer, from your phone to a laptop, does four jobs:

  1. Input: it takes something in. A key press, a tap, a photo from the camera.
  2. Processing: it works on it. The part that does this is the CPU (the processor).
  3. Memory and storage: it keeps things, for now or for later.
  4. Output: it gives something back. Text on the screen, a sound, a message sent.

Think of sending money with bKash. You type the amount (input). The app checks your balance and takes the money away (processing). Your new balance is kept (storage). The screen shows "Send money successful" (output).

A computer keeps things in two places.

  • RAM is like your study desk. Things you are using right now are on it. It is fast, but small, and everything on it is cleared when the power goes off.
  • Storage (the SSD or hard disk) is like your cupboard. It is slower, but much bigger, and things stay there after you switch off.

When you open a file, the computer copies it from the cupboard to the desk. When you press save, it puts it back in the cupboard. That is why unsaved work is lost in a power cut: it was only on the desk.

A program is a list of instructions the computer follows, one by one, in order. The computer is very fast, but it does exactly what the steps say, nothing more. It does not guess what you meant.

const price = 120;
const quantity = 3;
const total = price * quantity;
console.log(total);

This tiny program keeps two numbers in memory, multiplies them (processing) and shows 360 (output). You do not need to write code like this yet. Just notice: each line is one small, exact step.

People often think the computer "understands" what they want. It does not. If you tell a friend "bring the notes", they know which notes. A computer needs every detail: which file, which folder, which line. Most early errors come from a step that was almost right.

When you meet any app or any program, ask four questions: What goes in? What work is done? What is kept? What comes out? If you can answer them, you understand what the program is for.

Words to recognise
inputprocessingoutputCPURAMstorageprograminstruction
04 / 08

Code tour

Click a line number with a ring to read the note for that line.

script.js5 notes
1// A tiny bKash-style program
let balance = 1500;
Mentor note · line 2
The balance is kept in memory (RAM) while the program runs. In a real app it would also be saved to storage.
const amount = 200;
4
balance = balance - amount;
6
console.log("Send money successful");
console.log("New balance: " + balance);
05 / 08

Quick check

3 questions. Each one explains itself after you answer.

  1. 1 / 3You are typing an assignment and the power goes off before you save. Why is the new text lost?
  2. 2 / 3On a phone calculator you type 12 + 30 and see 42. Which part is the output?
  3. 3 / 3Why must a program spell out every step?
06 / 08

Explain it back

Only you can see this. Log in to keep it.0 words
07 / 08

How confident are you with What a computer actually does?

08 / 08

Done

You can now
Look at any app and say what its input, processing, memory and output are.
Next: Files, folders and paths Back to Phase 0
On this page
  1. 01What a computer actually does
  2. 02Watch & read
  3. 03Explanation
  4. 04Code tour
  5. 05Quick check
  6. 06Explain it back
  7. 07Confidence
  8. 08Done
Up next · 02 / 08Watch & read
Mamun Labs LearnFound a mistake on this page? Tell Mamun.
Mamun Labs Learn
JourneyGlossary
esc
  • Try “map”, “flexbox” or “state”.
Log in
Start learning
Log in to save your progress. Everything here works without an account.Log in to save progressLog in
Phase 0Getting started
6 topics · 1–2 wks
  1. 1What a computer actually does
  2. 2Files, folders and paths
  3. 3The terminal, step by step
  4. 4Set up VS Code and Node
  5. 5Git and GitHub basics
  6. 6Using AI as a study partner
JourneyPhase 0What a computer actually does
01 / 08Overview

What a computer actually does

You'll learn the four jobs every computer does, and why a program must be a list of exact steps.

Why it mattersEvery line of code you write later is an instruction for this machine. Knowing what it can do makes code less mysterious.
about 45 min
02 / 08

Watch & read

Start with the required ones. The others are there when you need them.

Video
How Computers Work: What makes a computer, a computer?Code.org · YouTube · 5 min · English
MMamun's noteWatch all of it. Five minutes, and it names the four jobs from this page.
Video
How Computers Work: CPU, memory, input and outputCode.org · YouTube · 5 min · English
MMamun's noteWatch all of it. Pause when they talk about memory and think of the desk and the cupboard.
Video
CS50x 2024, Lecture 0: algorithms and pseudocodeCS50 (Harvard) · YouTube · 14 min · English
MMamun's noteWatch 51:30 to 1:05:10 only, the phone book part. It shows why every step must be exact. You can skip the rest of the lecture for now.
VideoOptional
Memory and storage: Crash Course Computer Science #19Crash Course · YouTube · 12 min · English
MMamun's noteOnly if you are curious. It is fast and goes into history and hardware. You do not need the details to move on.
03 / 08

Explanation

You use a computer every day. But what is it actually doing when you tap, type or click?

Every computer, from your phone to a laptop, does four jobs:

  1. Input: it takes something in. A key press, a tap, a photo from the camera.
  2. Processing: it works on it. The part that does this is the CPU (the processor).
  3. Memory and storage: it keeps things, for now or for later.
  4. Output: it gives something back. Text on the screen, a sound, a message sent.

Think of sending money with bKash. You type the amount (input). The app checks your balance and takes the money away (processing). Your new balance is kept (storage). The screen shows "Send money successful" (output).

A computer keeps things in two places.

  • RAM is like your study desk. Things you are using right now are on it. It is fast, but small, and everything on it is cleared when the power goes off.
  • Storage (the SSD or hard disk) is like your cupboard. It is slower, but much bigger, and things stay there after you switch off.

When you open a file, the computer copies it from the cupboard to the desk. When you press save, it puts it back in the cupboard. That is why unsaved work is lost in a power cut: it was only on the desk.

A program is a list of instructions the computer follows, one by one, in order. The computer is very fast, but it does exactly what the steps say, nothing more. It does not guess what you meant.

const price = 120;
const quantity = 3;
const total = price * quantity;
console.log(total);

This tiny program keeps two numbers in memory, multiplies them (processing) and shows 360 (output). You do not need to write code like this yet. Just notice: each line is one small, exact step.

People often think the computer "understands" what they want. It does not. If you tell a friend "bring the notes", they know which notes. A computer needs every detail: which file, which folder, which line. Most early errors come from a step that was almost right.

When you meet any app or any program, ask four questions: What goes in? What work is done? What is kept? What comes out? If you can answer them, you understand what the program is for.

Words to recognise
inputprocessingoutputCPURAMstorageprograminstruction
04 / 08

Code tour

Click a line number with a ring to read the note for that line.

script.js5 notes
1// A tiny bKash-style program
let balance = 1500;
Mentor note · line 2
The balance is kept in memory (RAM) while the program runs. In a real app it would also be saved to storage.
const amount = 200;
4
balance = balance - amount;
6
console.log("Send money successful");
console.log("New balance: " + balance);
05 / 08

Quick check

3 questions. Each one explains itself after you answer.

  1. 1 / 3You are typing an assignment and the power goes off before you save. Why is the new text lost?
  2. 2 / 3On a phone calculator you type 12 + 30 and see 42. Which part is the output?
  3. 3 / 3Why must a program spell out every step?
06 / 08

Explain it back

Only you can see this. Log in to keep it.0 words
07 / 08

How confident are you with What a computer actually does?

08 / 08

Done

You can now
Look at any app and say what its input, processing, memory and output are.
Next: Files, folders and paths Back to Phase 0
On this page
  1. 01What a computer actually does
  2. 02Watch & read
  3. 03Explanation
  4. 04Code tour
  5. 05Quick check
  6. 06Explain it back
  7. 07Confidence
  8. 08Done
Up next · 02 / 08Watch & read

You use a computer every day. But what is it actually doing when you tap, type or click?

Every computer, from your phone to a laptop, does four jobs:

  1. Input: it takes something in. A key press, a tap, a photo from the camera.
  2. Processing: it works on it. The part that does this is the CPU (the processor).
  3. Memory and storage: it keeps things, for now or for later.
  4. Output: it gives something back. Text on the screen, a sound, a message sent.

Think of sending money with bKash. You type the amount (input). The app checks your balance and takes the money away (processing). Your new balance is kept (storage). The screen shows "Send money successful" (output).

A computer keeps things in two places.

  • RAM is like your study desk. Things you are using right now are on it. It is fast, but small, and everything on it is cleared when the power goes off.
  • Storage (the SSD or hard disk) is like your cupboard. It is slower, but much bigger, and things stay there after you switch off.

When you open a file, the computer copies it from the cupboard to the desk. When you press save, it puts it back in the cupboard. That is why unsaved work is lost in a power cut: it was only on the desk.

A program is a list of instructions the computer follows, one by one, in order. The computer is very fast, but it does exactly what the steps say, nothing more. It does not guess what you meant.

const price = 120;
const quantity = 3;
const total = price * quantity;
console.log(total);

This tiny program keeps two numbers in memory, multiplies them (processing) and shows 360 (output). You do not need to write code like this yet. Just notice: each line is one small, exact step.

People often think the computer "understands" what they want. It does not. If you tell a friend "bring the notes", they know which notes. A computer needs every detail: which file, which folder, which line. Most early errors come from a step that was almost right.

When you meet any app or any program, ask four questions: What goes in? What work is done? What is kept? What comes out? If you can answer them, you understand what the program is for.

Words to recognise
inputprocessingoutputCPURAMstorageprograminstruction

You use a computer every day. But what is it actually doing when you tap, type or click?

Every computer, from your phone to a laptop, does four jobs:

  1. Input: it takes something in. A key press, a tap, a photo from the camera.
  2. Processing: it works on it. The part that does this is the CPU (the processor).
  3. Memory and storage: it keeps things, for now or for later.
  4. Output: it gives something back. Text on the screen, a sound, a message sent.

Think of sending money with bKash. You type the amount (input). The app checks your balance and takes the money away (processing). Your new balance is kept (storage). The screen shows "Send money successful" (output).

A computer keeps things in two places.

  • RAM is like your study desk. Things you are using right now are on it. It is fast, but small, and everything on it is cleared when the power goes off.
  • Storage (the SSD or hard disk) is like your cupboard. It is slower, but much bigger, and things stay there after you switch off.

When you open a file, the computer copies it from the cupboard to the desk. When you press save, it puts it back in the cupboard. That is why unsaved work is lost in a power cut: it was only on the desk.

A program is a list of instructions the computer follows, one by one, in order. The computer is very fast, but it does exactly what the steps say, nothing more. It does not guess what you meant.

const price = 120;
const quantity = 3;
const total = price * quantity;
console.log(total);

This tiny program keeps two numbers in memory, multiplies them (processing) and shows 360 (output). You do not need to write code like this yet. Just notice: each line is one small, exact step.

People often think the computer "understands" what they want. It does not. If you tell a friend "bring the notes", they know which notes. A computer needs every detail: which file, which folder, which line. Most early errors come from a step that was almost right.

When you meet any app or any program, ask four questions: What goes in? What work is done? What is kept? What comes out? If you can answer them, you understand what the program is for.

Words to recognise
inputprocessingoutputCPURAMstorageprograminstruction