0.4IT vocabulary & digital basics
The essentials in 30 seconds
- Bit = smallest unit (0/1); byte = 8 bits; KB → MB → GB → TB, each about a thousand times the previous.
- Storage (in bytes) ≠ bandwidth (in bits per second): the classic units trap.
- A file has a format, shown by its extension (.pdf, .jpg), which tells software how to open it.
Running mini-case — Sofiane calms an unhappy user in Algiers
A user at the distribution SME in Algiers complains to Sofiane: "my 100 Mb/s plan doesn't even download at 100 MB/s, they sold me a slow line". Sofiane stays calm: the plan is in megabits, the download is displayed in megabytes. Since one byte equals 8 bits, 100 Mb/s gives about 12 MB/s at best, minus network and Wi-Fi losses. It is not a fault. He takes the chance to explain the difference between storage (the quantity, in bytes) and bandwidth (the speed, in bits per second), and why a file's extension indicates how to open it.
Standalone case for this section: it returns in the course, the diagram, the script and the 48h challenge of section 0.4.
1. From bit to byte
Everything rests on the bit — a single 1 or 0, the smallest unit of information. Eight bits form a byte, the base unit of the size of data: KB, MB, GB, TB, each worth about a thousand times the previous. Files, photos and programs are measured in bytes. Sofiane reads these units every day when he talks about disk space.
2. Storage ≠ bandwidth (the classic trap)
We often confuse storage (measured in bytes) and bandwidth (measured in bits per second, e.g. Mb/s). Since one byte equals 8 bits, a "100 Mb/s" line transfers at best about 12 MB/s, not 100 — hence the impression that a download is "slower" than the advertised speed. Sofiane uses this rule to explain a user complaint.
3. Files, formats and file systems
A file has a format shown by its extension (.pdf, .jpg, .docx) which tells software how to open it. The file system organises data into files and folders on a storage medium. Sofiane checks the extension before opening or converting a file.
🔎 Concrete example — 🔎 Concrete example — Why 100 Mb/s ≠ 100 MB/s
Sofiane works through the calculation in front of the unhappy user:
100 Mb/s ÷ 8 ≈ 12.5 MB/s at best
(− network, Wi-Fi, remote server losses)
→ plan in megabits, download in megabytes.Reading: the plan is in megabits, downloads are displayed in megabytes. One byte = 8 bits.
Lesson: seeing ~11-12 MB/s on a 100 Mb/s line is normal, not a fault.
Section vocabulary
- Bit
- The smallest unit of information: a single 1 or 0.
Simple example: Sofiane explains that a byte is eight bits.
What it is not: a unit of network speed.
Reflex: smallest unit → bit.
- Byte
- Eight bits; the base unit of data size (KB, MB, GB, TB).
Simple example: Sofiane reads a file's size in megabytes.
What it is not: a measure of bandwidth in bits per second.
Reflex: data size → byte.
- Storage vs bandwidth
- Storage is measured in bytes (quantity); bandwidth in bits per second (speed).
Simple example: Sofiane distinguishes a file's size from the line's speed.
What it is not: two names for the same quantity.
Reflex: quantity in bytes; speed in bits/s.
- Format / extension
- A file's type, shown by its extension (.pdf, .jpg), which tells software how to open it.
Simple example: Sofiane checks the extension before opening the file.
What it is not: a detail of no importance on a file.
Reflex: open a file → read its extension.
- File system
- The way the OS organises data into files and folders.
Simple example: Sofiane finds his shared folders on the SME server.
What it is not: a word processing software.
Reflex: organise files and folders → file system.
In practice — In practice — Reading units correctly
- Find the size of a few files and note whether it is in KB, MB or GB, like Sofiane.
- Check a disk's free space, in GB or TB.
- Note your connection speed in Mb/s, then divide by 8 to estimate the real MB/s.
- Explain in one sentence why a 1 GB download is not instant on 100 Mb/s.
Step-by-step script — reading units like Sofiane (5 min)
1) Note a file's size: in KB, MB or GB? 2) Note a disk's free space: in GB or TB? 3) Note your line's bandwidth in Mb/s and divide by 8 for MB/s. 4) Explain why 100 Mb/s ≈ 12 MB/s at best. 5) Check a file's extension before opening it.
Remember the order of the units and the storage/bandwidth distinction: that is what avoids real mistakes.
Copy-paste template — my units map
Running thread: Sofiane, support technician — distribution SME in Algiers.
Bit = smallest unit; byte = 8 bits.
Size: KB < MB < GB < TB (~×1000).
Storage = bytes (quantity); bandwidth = bits/s (speed).
Bandwidth: Mb/s ÷ 8 ≈ MB/s. A file's format = its extension.User complaint
Sofiane calmly explains a gap between advertised bandwidth and real download.
Disk space
Sofiane reads file sizes and free space in KB, MB, GB, TB.
Bandwidth conversion
Sofiane divides a bandwidth in Mb/s by 8 to estimate MB/s.
File format
Sofiane checks the extension before opening or converting a file.
✓ Best practices
- Remember the order: KB < MB < GB < TB.
- Divide a bandwidth in Mb/s by 8 to get MB/s.
- Read the extension to know the format.
✗ Common pitfalls
- Confusing megabit (bandwidth) and megabyte (size).
- Believing a 100 Mb/s line gives 100 MB/s.
- Ignoring a file's extension.
Key takeaways
- Bit = smallest unit; byte = 8 bits; KB → MB → GB → TB (~×1000).
- Storage in bytes; bandwidth in bits per second — do not confuse them.
- One byte = 8 bits: divide an Mb/s by 8 for MB/s.
- The extension indicates the file's format.
48h challenge — apply it tomorrow
Like Sofiane, take the advertised bandwidth of your line (e.g. 100 Mb/s) and divide it by 8 to estimate the real MB/s. Then note the size of a file you often handle and its extension: explain in one sentence why stored quantity and transfer speed are not measured in the same unit.
- I distinguish the bit, the byte and the order of the units (KB → MB → GB → TB).
- I separate storage (bytes) and bandwidth (bits per second).
- I convert a bandwidth in Mb/s to MB/s and I read a file's extension.
Frequently asked questions
Why does my 100 Mb/s line never download at 100 MB/s?
Because they are two units: the plan is in megabits/s, downloads in megabytes/s. One byte = 8 bits, so 100 Mb/s ≈ 12 MB/s at best, minus network and Wi-Fi losses.
Do I need to memorise all the conversions?
No: remember the order of the units and the storage/bandwidth distinction. That is what avoids real mistakes (undersizing a disk, misreading a bandwidth), as Sofiane explains.
What exactly does "one byte = 8 bits" mean?