Intro to Computer Science / Unit 1: Computing Systems
1.4 Memory and Storage
Notes
Computers use different kinds of memory that trade off speed, size and cost.
- RAM is volatile: it loses its data when power is off. It is much faster than storage.
- Storage is non-volatile: an SSD, hard drive or USB drive keeps data without power.
- An SSD has no moving parts and is faster than a hard disk drive (HDD), which uses spinning disks.
- Cache is a very small, very fast memory close to the CPU.
- Units: 1 byte = 8 bits; a kilobyte is about 1,000 bytes, a megabyte about 1,000 KB, a gigabyte about 1,000 MB, and a terabyte about 1,000 GB.
- Example: a 2 TB drive holds about 2,000 GB of data.
Practice
What does it mean that RAM is volatile?
Volatile memory needs power to hold data.
Which is the correct order from smallest to largest unit?
Each unit is about 1,000 times larger than the one before it.
A laptop feels slow when many programs are open and the RAM is full. What is the best upgrade?
More RAM lets more programs and data stay in fast memory at once.
Ready for more? Take the Unit 1 test.