C. Computer Environments and Systems · Computer Environments and Systems

Inside the Computer: Internal Components and Their Specifications

C1.1About 70 minutes

Learning goals

I can name the main internal components of a computer (CPU, RAM, ROM, cache, storage drive, motherboard, power supply, video card and sound card) and describe what each one does.
I can tell volatile memory from non-volatile storage and explain why a computer needs both.
I can read the key specification of each component and its unit (GHz, GB, TB, W).
I can explain which components matter most for a given user's needs.

Words to know

hardware
The physical parts of a computer that you can touch.

CPU (central processing unit)
The processor: the chip that carries out program instructions. Key specs: number of cores, clock speed (GHz) and cache size.

RAM (random access memory)
Fast working memory that holds the programs and data in use right now. It is volatile: it is erased when the power goes off.

ROM (read-only memory)
Non-volatile memory on the motherboard that holds the firmware (UEFI or BIOS) the computer runs when it first turns on.

cache
A small amount of very fast memory inside the CPU that keeps copies of the data and instructions used most often.

storage drive
A hard disk drive (HDD) or solid-state drive (SSD) that keeps programs and files even when the power is off.

motherboard
The main circuit board. Every other component plugs into it or connects to it.

power supply unit (PSU)
Converts alternating current (AC) from the wall outlet into the low-voltage direct current (DC) the parts need. Rated in watts (W).

GPU (graphics processing unit)
The processor that draws images for the monitor. It may be built into the CPU (integrated) or on a separate video card (dedicated).

volatile / non-volatile
Volatile memory loses its contents without power (RAM, cache). Non-volatile memory keeps them (ROM, SSD, HDD).

What is really inside the box?

Picture two Grade 11 students shopping for a laptop before school starts in September. One wants to edit hockey highlight videos. The other mostly writes essays and joins video calls. A salesperson rattles off "Core i5, 16 gigs of RAM, 512 SSD, integrated graphics." Is that a good deal? For which student?

To answer, you need to know what is inside a computer, what each part does, and what its numbers mean. This unit, Computer Environments and Systems, starts there. Later in the unit you will look at peripherals, how a program actually runs on the hardware, how to organize and protect your files, and the tools programmers use.

Remember from Grade 9

In Grade 9 math you wrote or changed short programs (often in Python) with variables, expressions and loops. In this course's Programming Basics unit you write many more. Every one of those programs runs on the hardware in this lesson. When you type score = 10, the number 10 is stored in RAM, and when you add to it, the CPU does the arithmetic. You will trace exactly how that happens in the lesson How a Program Runs on the Hardware.

The main internal components

Internal components are the parts inside the case. Each one has a job and a few specifications ("specs") that tell you how capable it is.

Motherboard. The main circuit board. It has a socket for the CPU, slots for RAM sticks, expansion slots for cards, connectors for drives, and the ports on the back. Its specs decide what else you can install: which CPUs fit, how much RAM it can hold, how many drives and cards it has room for.
CPU (central processing unit). The "brain" that carries out instructions. Specs: number of cores (each core can work on its own stream of instructions), clock speed in gigahertz (GHz, billions of cycles per second), and cache size in megabytes (MB).
Cache. A small amount of very fast memory built into the CPU. It keeps copies of the data the CPU is using most, so the CPU does not have to wait for RAM. Modern CPUs have levels: L1 (smallest, fastest), L2 and L3 (larger, a little slower).
RAM (random access memory). The computer's working memory. Every program that is open, and the data it is using, sits in RAM. Spec: capacity in gigabytes (GB), plus type and speed (for example DDR4 or DDR5). RAM is volatile: turn the power off and it is wiped.
ROM (read-only memory). A chip on the motherboard holding the firmware (called UEFI on modern computers, BIOS on older ones). When you press the power button, this firmware tests the hardware and then loads the operating system from the storage drive. ROM is non-volatile.
Storage drive. Keeps the operating system, programs and your files when the power is off. A hard disk drive (HDD) stores data magnetically on spinning platters. A solid-state drive (SSD) uses flash memory chips with no moving parts, so it is much faster, quieter and tougher. Spec: capacity in GB or terabytes (TB), and speed.
Power supply unit (PSU). Converts AC power from the wall outlet into low-voltage DC power. Spec: maximum output in watts (W). It must supply more than all the parts need together. (Laptops use an external adapter and a battery instead.)
Video card. Holds a GPU and its own memory (VRAM) and sends the picture to the monitor. Many computers use integrated graphics built into the CPU instead. A dedicated video card is much faster for 3-D games, video editing and machine learning.
Sound card. Converts digital sound data into the signal that drives speakers or headphones, and converts the microphone's signal into digital data. Almost every computer now has a sound chip built into the motherboard; separate sound cards or external audio interfaces are mostly used for music and recording studios.

A simplified map of a desktop computer (not to scale). The CPU, RAM and ROM sit on the motherboard; cards plug into expansion slots; the power supply and the storage drive connect to the board by cables or connectors.

Component	Main job	Key spec(s) and unit	Who needs more of it?
CPU	carries out instructions	cores; clock speed (GHz); cache (MB)	video editors, programmers compiling big projects, gamers
RAM	holds open programs and data	capacity (GB); type and speed (DDR5-5600, for example)	people with many apps or browser tabs open, video and photo editors
Storage drive	keeps files when off	capacity (GB or TB); SSD or HDD	anyone with a big photo, video or game library
Video card / GPU	draws the screen image	GPU model; VRAM (GB)	3-D gamers, video editors, 3-D designers, machine-learning students
Power supply	powers every part	maximum output (W)	systems with powerful CPUs and video cards
Motherboard	connects everything	CPU socket; RAM slots and maximum RAM; expansion slots; ports	anyone who plans to upgrade later
Sound card	turns data into sound and back	audio quality; inputs and outputs	musicians, podcasters, sound designers

Each internal component, what it does, and the spec to read on a product page.

Memory versus storage

People often say "memory" when they mean storage, but they are different.

Memory (RAM) is where the computer works. It is fast, but it is volatile and it is smaller.
Storage (SSD or HDD) is where the computer keeps things. It is slower, but it is non-volatile and much larger.

Think of a student doing homework at a kitchen table. The table is RAM: everything you are working on right now is spread out on it, and you can reach it instantly. The bookshelf in the next room is storage: it holds far more, but each trip takes longer. The few notes in your hand are the cache. (Inside the CPU there are even smaller, faster storage spots called registers: they are like the number you are holding in your head while you calculate.) If the table is too small (not enough RAM), you keep running to the shelf and back, and everything slows down. Computers do the same thing: when RAM is full, the operating system moves data to storage and back, which is much slower.

The memory hierarchy. Near the top, memory is faster but holds less and costs more per gigabyte. Near the bottom, it is bigger and cheaper but slower. Only storage at the bottom keeps data when the power is off.

Worked example

Example 1: Which component is the bottleneck?

Amira edits 4K video on her laptop. It has a 6-core CPU, 8 GB of RAM, a 1 TB SSD and integrated graphics. When she has her editor, a browser and music open, everything freezes for a second or two. The storage drive is only half full. Which component should she upgrade first, and why?

List what each symptom points to. Freezing when several programs are open means the computer is running out of working space, which points to RAM.
Check the other parts. A half-full 1 TB SSD is fast and has room, so storage is not the problem. A 6-core CPU is reasonable. Integrated graphics would slow down exporting and effects, but would not cause freezes when switching apps.
8 GB of RAM is low for 4K video editing plus other programs. When RAM fills up, the operating system moves data to the SSD and back, which causes the pauses.
So the first upgrade is more RAM (for example 16 GB or 32 GB), if her laptop's RAM can be upgraded. Many thin laptops have RAM soldered to the motherboard, so she should check before buying.

Upgrade the RAM. The symptom (freezing with many programs open) and her low 8 GB match; the other specs are adequate. A dedicated GPU would be her second upgrade, for faster exports.

Worked example

Example 2: Volatile or non-volatile?

Sort these into volatile and non-volatile, and say what happens to each when the power cuts out during a snowstorm: RAM, cache, ROM firmware, SSD, HDD.

Volatile memory needs power to hold its contents: RAM and cache. When the power cuts out, everything in them is lost, including any unsaved work in an open document.
Non-volatile memory keeps its contents without power: ROM, the SSD and the HDD.
That is why programs ask you to save: saving copies your work from RAM to the storage drive.

Volatile: RAM, cache. Non-volatile: ROM, SSD, HDD. Unsaved work in RAM is lost in a power cut; saved files on the drive are safe.

Just for fun

The CPU and the RAM had an argument during a power outage. When the lights came back on, the RAM had completely forgotten what it was about. (That is what volatile means.)

Hands-on activity

Find your computer's internal specs (no screwdriver needed)

You need: any computer you are allowed to use (a laptop, desktop or Chromebook). Do not open the case. Opening a computer can damage it and can void the warranty, and the power supply inside a desktop can hold a dangerous charge; leave that to a grown-up or a technician.

Where to find the system information: on Windows, Settings → System → About (for more detail, open Task Manager with Ctrl + Shift + Esc and choose the Performance tab); on macOS, Apple menu → About This Mac, then More Info or System Report; on ChromeOS, type chrome://system in the address bar.

Open the system information for your computer.
Record in a table: the CPU name, number of cores, base clock speed, amount of RAM, storage type and capacity, and the graphics (integrated or dedicated).
Open the CPU and memory graphs (Task Manager's Performance tab, Activity Monitor on a Mac). Open three or four programs and a video. Watch the memory use climb.
Write two sentences: Which user from this lesson (essay writer, video editor, gamer) is this computer best suited for? Which component would you upgrade first, and why?

What to look for: a correct table with units (GHz, GB, TB) and a recommendation that matches a component to a need, such as "8 GB of RAM is fine for essays and video calls, but a video editor would need more RAM and a dedicated GPU."

Your turn

Name the component that carries out program instructions, and give two of its specifications.

What is the difference between RAM and an SSD?

What does the firmware in ROM do when you press the power button?

Why is cache built inside the CPU instead of being part of RAM?

A power supply is rated 550 W. The parts together draw about 400 W at full load. Is the power supply big enough? Explain.

Give one reason a person might choose an HDD instead of an SSD.

Which two components would you look at first for a student who plays 3-D games?

More practice: warm-up

What does the abbreviation RAM stand for?

Which component converts AC from the wall outlet into DC for the computer's parts?

What is the main circuit board called?

Is cache volatile or non-volatile?

What does an SSD have that makes it faster and tougher than an HDD?

More practice: on your own

A friend says, "My laptop has 512 GB of memory." What do they most likely mean? Rewrite the sentence correctly.

Explain why a computer with a fast CPU can still feel slow if it has too little RAM.

Why do many thin laptops not allow RAM upgrades? What should a buyer do about it?

A musician records podcasts with two microphones. Which internal component (or external alternative) matters most for her, and why?

Rank these from fastest to slowest: RAM, HDD, L1 cache, SSD.

Challenge

A desktop has a 6-core CPU, 32 GB of RAM, a 2 TB HDD as its only drive, and a dedicated GPU. Its owner says it takes almost two minutes to start up and programs open slowly, but once a game is running it plays smoothly. Diagnose the problem and recommend one change.

Explain, using the words volatile and non-volatile, why a computer needs ROM even though it already has RAM and an SSD.

A school is choosing between Computer A (4 cores, 3.5 GHz, 8 GB RAM, 256 GB SSD, integrated graphics) and Computer B (8 cores, 3.0 GHz, 16 GB RAM, 512 GB SSD, integrated graphics) for a computer science lab where students run an IDE, a browser and sometimes small games they write. Which would you choose? Give two reasons, and say one thing that does not decide it.

Check your understanding

Quiz

Which component holds the programs and data that are in use right now and is erased when the power goes off?

What is the job of the firmware stored in ROM?

A CPU is described as "8 cores, 3.2 GHz". What does 3.2 GHz measure?

Which list is in order from fastest to slowest?

A video editor's computer has plenty of RAM and a fast SSD, but exporting videos and adding effects are slow. It has integrated graphics. Which upgrade is most likely to help?

Why does a desktop's power supply need a wattage rating higher than the total power the parts use?

For parents and teachers

Big idea: Expectation C1.1 asks students to relate the specifications of internal components (CPU, RAM, ROM, cache, hard drive, motherboard, power supply, video card, sound card) to user requirements. The goal is not memorizing parts, but explaining which part matters for which user.

How to help: Look at a real product page or flyer together and ask your teen to explain each spec and who it suits. Ask "What would happen if this computer had half the RAM?" If you have an old computer that no longer works, a teacher or technician may be able to show the inside safely; please do not open a computer that is plugged in, and leave desktop power supplies closed (they can hold a charge).

Common difficulties:

Mixing up memory (RAM) and storage (SSD/HDD). Use the table-and-bookshelf comparison.
Thinking a higher number always means better. A higher clock speed can lose to more cores, and specs only matter in relation to what the user does.
Forgetting units: GHz for clock speed, GB for RAM, GB or TB for storage, W for power.
Thinking the sound card is always a separate card. On most computers it is a chip on the motherboard.