It is not uncommon for computers to have all memory slots occupied.
It is also important to note how many memory slots are available on your computer. Make sure you know exactly the type of RAM to buy for your computer. When buying a new computer or motherboard, pay close attention to the types of RAM the memory slots can accept. This picture has three open and available slots for three memory sticks. The picture below shows what memory slots may look like inside a desktop computer. The most common RAM types are SDRAM (synchronous dynamic random-access memory) and DDR (double data rate) for desktop computers and SO-DIMM (small outline dual in-line memory module) for laptop computers, each having various types and speeds. Most motherboards have two to four memory slots, which determine the type of RAM used with the computer. A memory slot, memory socket, or RAM slot allows RAM (random-access memory) to be inserted into the computer.
