Attendance Register Size, Printer Sharing and a Spreadsheet Flag
A coaching centre has five desktop computers and one printer. The printer has only a USB port. At present each computer is standalone: attendance is typed into separate spreadsheet files and carried between rooms on a pen drive. The centre wants one shared attendance register for 600 students. Each student record will contain: name (30 characters), roll number (10 characters), attendance percentage (3 characters) and fee status (1 character). The centre assumes 1 character = 1 byte and plans for 20% overhead per record. It also wants to add a 10 KB photograph for each student later. The centre has a broadband connection with a 2 Mbps upload speed and a Wi-Fi router with four LAN ports. A staff member suggests emailing the full file to all five computers every evening. Another suggests buying a USB switch so all computers can 'take turns' using the printer.
1. Estimate the register size without and with photographs. Using the 2 Mbps upload link, calculate the ideal upload time for the larger file and judge whether nightly emailing is practical.
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Without photographs: (30+10+3+1=44) bytes per record. For 600 records, (600\times44=26{,}400) bytes. Adding 20% overhead: (26{,}400\times1.2=31{,}680) bytes, about 31.7 KB (or about 30.9 KiB).
With photographs: (600\times10\text{ KB}=6{,}000\text{ KB}\approx5.86\text{ MB}) using 1 MB = 1024 KB. Add the register: about (5.86\text{ MB}+0.03\text{ MB}\approx5.89\text{ MB}).
Upload time at 2 Mbps: convert to bits, (5.89\times8\approx47.1) megabits. At 2 Mbps, (47.1/2\approx23.6) seconds ideal. Real overhead may make it 30–45 seconds.
So nightly email is technically practical for a single 5.9 MB file. The bigger problem is version control: five copies will diverge, and someone will edit the wrong file. A shared folder or a single file on one host is operationally safer than emailing copies.
2. Compare the USB-switch proposal with connecting the printer to one computer and enabling printer sharing. Which is the better low-cost choice, and what operating condition must be stated?
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A USB switch physically connects the printer to one computer at a time. It is cheap, but it is not true sharing: a user must walk to the switch, change the active computer, and wait. Print jobs from other machines cannot be queued unless that machine is selected. For five staff members this creates constant interruption.
Connecting the printer to one host PC and enabling printer sharing keeps the printer available over the LAN. The other four computers install the shared printer and send jobs to the host. The direct cost is nearly zero. The critical condition is that the host PC must remain switched on, connected to the LAN, and logged in with sharing enabled; if it sleeps or is shut down, printing stops. Drivers and permissions must also be configured.
For a low-cost office with an always-on reception computer, PC-sharing is the better choice. If no PC can stay on, a small network print server or a network printer is more reliable, at extra cost.
3. A student with attendance 72% is shown as 'Promote' by the formula D2=IF(C2<75,"Detain","Promote"). The formula is copied down correctly. Diagnose the most likely cause and give a fix.
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The most likely cause is that C2 is stored as text, for example entered as '72% or "72%" rather than as the number 72. In many spreadsheets, text values are treated as greater than any number in comparisons, so C2<75 evaluates to FALSE and the IF returns "Promote". A left-aligned value in a column of right-aligned numbers is a quick visual clue; ISNUMBER(C2) confirms it.
Fixes:
- Best: enter attendance as a numeric value, e.g.
72, not72%with an apostrophe. - If the text includes a percent sign, convert it:
=IF(VALUE(SUBSTITUTE(C2,"%",""))<75,"Detain","Promote"). - If C2 is a true percentage stored as 0.72, the threshold must be 0.75, not 75:
=IF(C2<0.75,"Detain","Promote").
The formula itself is syntactically fine; the data type is the bug.