Plant four display faults and time how long each takes to find

short · 45 min · Objective 5.1

Task

Create four reversible display faults and find each with the substitution order, recording the elapsed time -- because the ordering claim in the lesson is that cheap tests first is faster, and that is measurable.

Steps

  1. Record the working configuration in lab/disp/baseline.csv with header field,value covering resolution, refresh rate, scaling, input and which port the cable is in.
  2. Plant four faults one at a time, reversing each: wrong input selected on the display; cable in the motherboard port on a machine with a graphics card, or a different port; a resolution the display handles poorly; and scaling changed so the desktop is unusable.
  3. For each, record in lab/disp/faults.csv with header fault,symptom,step_that_found_it,seconds,cost_of_that_step.
  4. Record in lab/disp/order.md whether the cheap-first order found all four faster than a likelihood-first order would have, using your own timings.
  5. Restore the baseline and confirm every field matches, recording the confirmation in lab/disp/restored.csv with the same header as the baseline.

Verify

awk -F, 'NR>1 && NF>=2 {n++} END {print n" baseline field(s)"}' lab/disp/baseline.csv
awk -F, 'NR>1 && NF>=5 {n++} END {print n" fault(s) found"}' lab/disp/faults.csv
awk -F, 'NR>1 {s+=$4} END {print s" seconds total"}' lab/disp/faults.csv
awk -F, 'NR>1 {print $5}' lab/disp/faults.csv | sort -u | wc -l
grep -c . lab/disp/order.md
awk -F, 'NR>1 && NF>=2 {n++} END {print n" field(s) restored"}' lab/disp/restored.csv

Five baseline fields, four faults with timings, at least two distinct cost bands, an ordering note, and a restore whose field count matches the baseline. If every fault took the same time, the faults were too similar to test an ordering claim.

Notes

Reversing the scaling fault is harder than creating it, which is itself worth experiencing: a machine whose desktop is unusable still has a keyboard, and knowing the recovery path before you need it is the point.

This is an independent study companion for CompTIA A+ Core 1 220-1201 and is not produced by or endorsed by CompTIA.