What goes inside a PC case

A working PC needs seven essential parts: a motherboard, a CPU (processor), RAM (memory), a storage drive, a power supply, a case, and a graphics card (though some CPUs have one built in). Everything else — cooling fans, extra storage, wireless cards — plugs into or sits alongside these core components. The motherboard is the main circuit board that everything connects to. The CPU does the actual computing. RAM holds data while you're using it. The storage drive (SSD or hard drive) holds your files permanently. The power supply converts wall power into the right voltage for each part. The case holds everything and protects it. The graphics card processes images and video, either as a separate card or built into the CPU.

You cannot build a working PC without all seven of these parts. A PC with a broken graphics card can still run if the CPU has integrated graphics, but a PC without a motherboard or power supply will not turn on at all. The parts you choose determine what your PC can do — a gaming build needs a more powerful graphics card and CPU than a web browsing build, but the basic structure is the same.

Key Takeaways

  • Every PC needs a motherboard, CPU, RAM, storage drive, power supply, case, and graphics card — you cannot skip any of these seven parts.
  • The motherboard is the main board everything plugs into, and its size and socket type determine what CPU and RAM you can use.
  • Your CPU and graphics card are the most expensive parts and have the biggest effect on what your PC can do.
  • Storage drives come in two types — SSDs are faster and more common now, while hard drives are cheaper but slower.
  • The power supply wattage must be high enough for your CPU and graphics card combined, plus some headroom.

The motherboard: where everything connects

The motherboard is a large circuit board with slots and connectors for every other part. The CPU socket is where your processor sits. RAM slots hold your memory sticks. The power connectors take power from the power supply and distribute it to every part. Storage drives and graphics cards plug into the motherboard through different types of connectors. The motherboard also has a BIOS chip that stores your PC's basic settings and boots the system when you turn it on.

Motherboards come in different sizes. ATX is the standard full-size board. Micro-ATX is smaller and fits in smaller cases. Mini-ITX is the smallest and is used for compact builds. The size you choose affects what case you need and how many expansion slots you have. Motherboards also have different socket types — an Intel motherboard uses an Intel socket, and an AMD motherboard uses an AMD socket. Your CPU must match your motherboard's socket, so you choose the CPU and motherboard together.

The CPU: the processor that does the work

The CPU (central processing unit) is the processor that runs your programs and handles calculations. It sits in a socket on the motherboard and is covered by a cooler (usually a fan or liquid cooling system). Intel and AMD are the two main CPU makers. Intel CPUs use Intel sockets, and AMD CPUs use AMD sockets — you cannot mix them. The CPU you choose determines what motherboard socket you need.

CPUs vary widely in power and price. A budget CPU for web browsing and office work costs $100 to $200. A mid-range CPU for gaming or video editing costs $300 to $500. High-end CPUs for professional work can cost $1,000 or more. Some CPUs have integrated graphics built in, which means you do not need a separate graphics card for basic use. Others require a separate graphics card to display anything on screen. The CPU generates heat, so it always needs a cooler — either an air cooler (a fan and heatsink) or a liquid cooler (tubes and a pump).

RAM: temporary memory while your PC runs

RAM (random access memory) is temporary memory that your PC uses while it is running. It holds the data your programs are actively using. When you turn off your PC, RAM empties completely. RAM comes in sticks that plug into vertical slots on the motherboard. Most modern PCs use DDR4 or DDR5 RAM — the motherboard determines which type you need. You cannot use DDR4 RAM in a DDR5 motherboard or vice versa.

Most PCs need 16 GB of RAM for comfortable everyday use and gaming. Budget builds use 8 GB. Professional video editing or 3D rendering may need 32 GB or more. RAM is relatively cheap compared to the CPU or graphics card, so it is often worth buying more than the minimum. RAM sticks usually come in pairs, and most motherboards have four slots, so you can add more later if you need it.

Storage drives: where your files live permanently

A storage drive holds your operating system, programs, and files permanently. When you turn off your PC, the data stays on the drive. There are two main types: SSDs (solid state drives) and hard drives. SSDs are much faster — your PC boots in seconds and programs open instantly. Hard drives are slower but cheaper per gigabyte. Most new PCs use at least one SSD for the operating system and programs, and many add a hard drive for extra storage.

SSDs connect through M.2 slots (the most common type now) or 2.5-inch SATA connectors. Hard drives use 3.5-inch SATA connectors. A typical PC needs at least 500 GB of storage for the operating system and basic programs, but 1 TB is more comfortable. If you store large video files, photo libraries, or game libraries, you may need 2 TB or more. You can add a second drive later, so you do not have to buy all your storage at once.

The power supply: converting wall power for your parts

The power supply converts electricity from your wall outlet into the right voltage and current for each part of your PC. It has cables that connect to the motherboard, CPU, graphics card, and storage drives. The power supply's wattage rating tells you how much power it can deliver. A budget PC with no graphics card might need 400 to 500 watts. A gaming PC with a mid-range graphics card needs 650 to 750 watts. A high-end gaming PC with a powerful graphics card needs 850 watts or more.

Always buy a power supply with more wattage than your PC actually needs — running at 80 percent of capacity is safer than running at 100 percent. A 750-watt power supply is a safe choice for most gaming builds. Look for 80+ Bronze certification or higher, which means the power supply is reasonably efficient. Cheap power supplies can fail suddenly and damage your other parts, so it is worth spending extra on a reliable brand like Corsair, EVGA, or Seasonic.

The case: the box that holds everything

The case is the metal box that holds all your parts and protects them from dust and damage. Cases come in different sizes to match different motherboard sizes. An ATX case fits full-size ATX motherboards. A Micro-ATX case is smaller and fits Micro-ATX or Mini-ITX boards. A Mini-ITX case is the smallest and only fits Mini-ITX boards. The case size you choose affects how easy it is to build in and how much cooling airflow you get.

Cases also vary in how many fans they come with and how easy they are to work inside. A case with good cable management (spaces to hide cables) and removable panels makes building easier. Most cases come with one or two fans already installed, but you may want to add more for better cooling. Cases range from $50 for a basic model to $300 or more for high-end cases with lots of features. For a first build, a mid-range case ($80 to $150) usually offers good balance between price, ease of use, and cooling.

The graphics card: processing images and video

A graphics card processes images and video and sends them to your monitor. Some CPUs have integrated graphics built in, which is enough for web browsing, office work, and video playback. If you want to play games, edit video, or do 3D rendering, you need a separate graphics card. Graphics cards plug into a PCIe slot on the motherboard and draw power from the power supply through separate cables.

Graphics cards vary enormously in power and price. Budget cards for light gaming cost $150 to $300. Mid-range cards for comfortable 1440p gaming cost $400 to $700. High-end cards for 4K gaming or professional work cost $800 or more. The graphics card you choose has the biggest effect on gaming performance. If you are not gaming, you may not need a separate graphics card at all — the integrated graphics in your CPU will be enough. If you do buy a graphics card, make sure your power supply has enough wattage and the right power connectors for it.

Frequently Asked Questions

Do I need a graphics card if I am not gaming?

No. Most CPUs have integrated graphics that are enough for web browsing, office work, video playback, and photo editing. You only need a separate graphics card if you want to play games, edit video professionally, or do 3D rendering. A separate card also lets you use multiple monitors more smoothly.

What happens if I buy a power supply that is too weak?

Your PC may not turn on at all, or it may turn on but shut down randomly under load. A power supply that is too weak can also damage your other parts over time. It is always safer to buy a power supply with more wattage than you think you need — a 750-watt supply for a 650-watt build is better than a 650-watt supply for a 650-watt build.

Can I upgrade parts later?

Yes. You can add more RAM, swap out the storage drive for a larger one, or add a graphics card later. The CPU and motherboard are harder to upgrade because changing the CPU usually means changing the motherboard too. Plan your first build with room to grow — buy a case and power supply with extra space and wattage so you can add parts later.

What is the difference between DDR4 and DDR5 RAM?

DDR5 is newer and faster than DDR4, but it is also more expensive. Your motherboard determines which type you need — you cannot use DDR4 in a DDR5 motherboard or vice versa. For most uses, DDR4 is still a good choice and costs less. DDR5 is worth considering if you are building a high-end PC or want your build to stay current longer.

Do I need to buy cooling fans separately?

Your CPU always comes with a cooler or needs one installed. Most cases come with one or two fans already. For a budget build in a well-ventilated case, the stock cooler and case fans are usually enough. For a gaming build or a case with poor airflow, adding extra fans (usually $15 to $30 each) can help keep temperatures down and make your PC quieter.