Directions
- The floor: Section 1 of the classwork form, all four files.
- Order: discussion form first, then Reading 2, then the classwork form. Do them in this order.
- Exit ticket: yes. It opens 20 minutes before the bell, pops up at 15, and locks your Chromebook until you submit.
- Submit the classwork form before the exit ticket pops up. You can reopen it and resubmit later.
- Past the floor: Section 2, then legitimate work for another class.
How Small Is Smaller
This reading explains the units that measure the size of a file, from the smallest to the largest.
From Bits to Gigabytes
The smallest unit of digital storage in this reading is the bit. A byte is a group of 8 bits, and file sizes are usually counted in bytes or in larger units built from bytes. A kilobyte (KB) is 1,000 bytes, a megabyte (MB) is 1,000,000 bytes, and a gigabyte (GB) is 1,000,000,000 bytes. From the byte upward, each unit is therefore exactly 1,000 times larger than the unit before it. Some computer programs and operating systems count a kilobyte as 1,024 bytes instead, so two different devices can display slightly different numbers for the same file. The CompTIA Tech+ exam lists the bit, the byte, the KB and the GB among the storage units that it tests.
Measuring the Three Saves
Figure 1 shows one photograph saved three times at different quality settings, and each save produced a file of a different size. Save 1 is 686,688 bytes, which is between 686 KB and 687 KB and less than 1 MB. Save 2, at 190,572 bytes, falls between 190 KB and 191 KB, and save 3, at 85,533 bytes, falls between 85 KB and 86 KB. Measured in bits, save 3 is 684,264 bits, because each of its 85,533 bytes holds 8 bits.
Because save 3 is the smallest of the three files, a fixed amount of storage can hold more copies of it than of either of the others. One gigabyte holds 11,691 complete copies of save 3, with 33,697 bytes remaining, while the same gigabyte holds only 5,247 copies of save 2 and 1,456 copies of save 1. A phone with 64 GB of free space could therefore hold 748,249 copies of save 3, 335,831 copies of save 2 or 93,200 copies of save 1. The smaller file comes at a cost, however, because save 3 also preserved the least detail of the three photographs.
Sources: NIST, The Binary Prefixes (n.d.); Deutsch, RFC 1951 (1996); CompTIA, Tech+ Certification (2024); classroom data, Three JPEG Saves (2026).
MC 1. (File 1 · zipped essay) You save an essay as a ZIP file. Is that lossless or lossy compression?
- Lossless
- Lossy
MC 2. (File 1 · zipped essay) Can you rebuild the original essay exactly from the ZIP file?
- Yes
- No
MC 3. (File 2 · JPEG photo) You save a photo as a JPEG. Is that lossless or lossy compression?
- Lossless
- Lossy
MC 4. (File 2 · JPEG photo) Can you rebuild the original photo exactly from the JPEG?
- Yes
- No
MC 5. (File 3 · song from a streaming app) You play a song in a streaming app on its normal setting. The app lists Lossless as a separate setting. Is the normal setting lossless or lossy compression?
- Lossless
- Lossy
MC 6. (File 3 · song from a streaming app) Can you rebuild the original recording exactly from the song on the normal setting?
- Yes
- No
MC 7. (File 4 · screenshot of a screenshot) Look at the chain in Figure 1. Each step shrinks the picture and saves it as a JPEG again. Is that lossless or lossy compression?
- Lossless
- Lossy
MC 8. (File 4 · screenshot of a screenshot) Can you rebuild the original picture exactly from screenshot 4?
- Yes
- No
CR 1. Put these five file sizes in order from smallest to largest: 1 GB, 686,688 bytes, 3 MB, 1 KB, 85,533 bytes. Use the units from How Small Is Smaller.
Write your answer in your lab notebook, labeled CR 1.
DO NOT CLICK OPEN FORM FROM A LAB COMPUTER
Open the exit ticketThis opens during your class period.