0.4IT vocabulary & digital basics
Every conversation in IT relies on a shared vocabulary about digital data. At the very bottom sits the bit — a single 1 or 0, the smallest unit of information. Eight bits make one byte, the basic unit for measuring data size: kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB), each roughly a thousand times the previous. Files, photos and programs are measured in bytes; the more they hold, the more bytes they take.
A classic and costly confusion is between storage (measured in bytes) and bandwidth or throughput (measured in bits per second, e.g. Mb/s). Because a byte is 8 bits, a « 100 Mb/s » connection transfers roughly 12 megaBYTES per second, not 100 — which is why a download can feel slower than the advertised speed suggests. Beyond units, you will constantly meet files and formats (the extension hints at the type: .docx, .pdf, .jpg), the idea of a file system organizing data into folders, and terms like hardware, software, driver and network. None of this is hard, but getting the words right early prevents a surprising number of mistakes later.
Section vocabulary
- Bit
- The smallest unit of information: a single 1 or 0.
- Byte
- Eight bits; the basic unit for data size (KB, MB, GB, TB).
- Storage vs bandwidth
- Storage is measured in bytes (how much you can keep); bandwidth in bits per second (how fast data moves).
- File format / extension
- The type of a file, hinted by its extension (.pdf, .jpg, .docx), which tells software how to open it.
- File system
- The way an OS organizes data into files and folders on a storage device.
What does it mean that a byte is 8 bits?
In practice — Read the units correctly
- Find the size of a few files on a machine and note whether they are in KB, MB or GB.
- Check the free space on a drive, in GB or TB.
- Look up your internet plan's speed in Mb/s, then divide by 8 to estimate real megabytes per second.
- Explain, in one sentence, why a 1 GB download is not instant on a 100 Mb/s line.
Key takeaways
- Bit = smallest unit (1/0); byte = 8 bits; KB → MB → GB → TB each ~1000x the last.
- Storage is in bytes; bandwidth is in bits per second — do not confuse the two.
- A byte is 8 bits, so divide a Mb/s figure by 8 to get real MB/s.
- A file's extension hints at its format, telling software how to open it.
Frequently asked questions
Why does my 100 Mb/s connection never download at 100 MB/s?
Because the two numbers use different units. Your plan is advertised in megaBITS per second (Mb/s), while download managers usually show megaBYTES per second (MB/s). Since one byte is eight bits, 100 Mb/s is at best around 12 MB/s. On top of that, real speed is reduced by protocol overhead, Wi-Fi conditions, the server you are downloading from, and other devices sharing the line. So seeing about 11–12 MB/s on a 100 Mb/s plan is normal and healthy, not a fault.
Do I really need to memorize all the units?
You do not need to memorize exact conversions, but you should internalize the order (KB < MB < GB < TB) and the storage-versus-bandwidth distinction, because those two ideas prevent real mistakes: under-sizing a disk, misreading a network speed, or mis-estimating how long a transfer will take. Everything else you can look up. The goal at this stage is fluency with the words, so that later sections about networks, backups and the cloud read naturally.