Grade by Grade
C. Computer Environments and Systems · Computer Environments and Systems

Choosing a Computer: Matching Specifications to User Requirements

C1.1 C1.2 C1.3About 70 minutes
Learning goals
  • I can gather a user's requirements by asking good questions.
  • I can read software minimum and recommended requirements and compare them with a computer's specs.
  • I can find the bottleneck in an unbalanced system.
  • I can use a weighted decision matrix (by hand and in Python) to recommend a computer and peripherals, and justify my choice.

Words to know

user requirements
What the user needs the computer to do, plus limits such as budget, portability and accessibility needs.
minimum requirements
The lowest specs a program needs to run at all.
recommended requirements
The specs a program needs to run well. Plan to meet these, not just the minimum.
bottleneck
The slowest part of a system, which limits the speed of the whole thing.
weighted decision matrix
A table that scores each option on several criteria, multiplies each score by how important that criterion is (its weight), and adds them up.
total cost of ownership
Purchase price plus running costs (ink, software subscriptions, repairs, power) over the life of the device.

The right computer is the one that fits the user

In the last three lessons you learned what every component and peripheral does and how to read its specs. Now you will use all of it the way a computer technician or IT consultant does: start with the user, not the hardware.

Imagine your aunt runs a small bakery in Sudbury. She asks you, "What computer should I buy?" The worst answer is "the most expensive one." The best answer starts with questions.

Step 1: Gather the requirements

Ask about:

  1. Tasks. What will they do every day? What will they do sometimes? (Email and spreadsheets? Video editing? Programming? Games?)
  2. Software. Which programs must run? Look up each program's minimum and recommended requirements.
  3. Where and how. At one desk or carried around? Is battery life important? Is there reliable internet?
  4. Peripherals. What must connect: printers, scanners, a second monitor, a drawing tablet, assistive devices?
  5. Budget. Including running costs (ink, software subscriptions, a backup drive).
  6. The future. How long should it last? Will they need to upgrade RAM or storage later?

In the Software Development unit you will see these same interviewing skills used to clarify the specifications for a program.

User taskSpec to prioritizeMany apps and browser tabsRAM (GB)3-D games, video effectsGPU / video cardBig photo and video libraryStorage capacity (TB)Fast start-up and loadingSSD instead of HDDCarrying it to school dailyweight, battery lifeLong video exports, compilingCPU cores and speed
Translate each user task into the spec that matters most. This is how you relate specifications to user requirements.

Step 2: Check software requirements

Software makers publish requirements. For example, a video-editing program might list:

  • Minimum: 4-core CPU, 8 GB RAM, integrated graphics, 10 GB free storage.
  • Recommended: 8-core CPU, 16 GB RAM (32 GB for 4K), dedicated GPU with 4 GB of VRAM, SSD.

A computer that only meets the minimum will run the program, but slowly. Since programs get more demanding with updates, aim for the recommended specs when you can. Also check the operating system and processor type: a program built only for Windows on x86-64 may not run on a Chromebook.

Step 3: Look for a balanced system (no bottlenecks)

A bottleneck is the slowest part of a system. It limits everything else, the way the narrow neck of a bottle limits how fast water pours out. A powerful GPU paired with 4 GB of RAM, or a fast CPU with a slow hard drive, wastes money: the user pays for speed they cannot use. A good recommendation spreads the budget so no single part holds the others back, with the most money going to the parts the user's tasks depend on.

Step 4: Compare options with a weighted decision matrix

When several computers could work, score them fairly:

  1. Choose the criteria (price, performance, portability, battery life...).
  2. Give each criterion a weight showing how important it is to this user (for example 1 to 5).
  3. Score each option on each criterion (1 to 5).
  4. Multiply each score by its weight and add. The highest total is the best match.

Here is a matrix for Maya, a Grade 11 student on a tight budget who carries her computer to school every day and runs an IDE and a browser.

Criterion (weight)Laptop ALaptop BDesktop C
Price (5)4 → 202 → 103 → 15
Performance (4)3 → 125 → 205 → 20
Portability (3)5 → 153 → 91 → 3
Battery life (3)5 → 153 → 91 → 3
Total (out of 75)624841
Each cell shows score → score × weight. The maximum total is 5 × (5 + 4 + 3 + 3) = 75. A desktop has no battery, so it gets the lowest score there.
Weighted score (out of 75)Laptop A62Laptop B48Desktop C4101530456075
The weighted totals from Maya's matrix. Laptop A wins because it scores well on what Maya cares about most (price and portability), even though it is not the most powerful.
criteria = ["price", "performance", "portability", "battery"]
weights = [5, 4, 3, 3]
names = ["Laptop A", "Laptop B", "Desktop C"]
scores = [[4, 3, 5, 5], [2, 5, 3, 3], [3, 5, 1, 1]]
best_name = ""
best_total = -1
for i in range(len(names)):
total = 0
for j in range(len(criteria)):
total = total + weights[j] * scores[i][j]
print(names[i], total)
if total > best_total:
best_total = total
best_name = names[i]
print("Best match:", best_name)

The decision matrix in Python, using lists and nested loops (lists are taught in the Arrays and Subprograms unit; scores here is a list of lists, one row per computer). Change the weights to model a different user. Output (one line each): Laptop A 62 / Laptop B 48 / Desktop C 41 / Best match: Laptop A

Worked example

Example 1: Find the bottleneck

A gaming PC has an 8-core CPU, a high-end video card, a 1 TB NVMe SSD, a 650 W power supply and 8 GB of RAM. The owner's games list "Recommended: 16 GB RAM." Games stutter when loading new areas. What is the bottleneck, and what would you recommend?

  1. Compare each spec with the requirement. CPU, GPU and SSD are strong. The power supply is reasonable for these parts.
  2. RAM is 8 GB, but the game recommends 16 GB. When RAM runs out, data has to come from the SSD instead, which is slower, so the game stutters.
  3. RAM is the bottleneck. Upgrading to 16 GB (or 32 GB) lets the rest of the expensive hardware work at full speed.

The bottleneck is the 8 GB of RAM. Upgrade to at least 16 GB to meet the recommended requirements.

Worked example

Example 2: A complete recommendation

Requirements for the Sudbury bakery: email, spreadsheets, a point-of-sale web app, printing receipts and invoices (about 400 black-and-white pages a month), and video calls with suppliers. The computer stays on the counter. Budget: about $1200 for everything. Write a recommendation.

  1. Tasks are light (office and web), so a mid-range CPU (4 to 6 cores) and 16 GB of RAM are plenty; 8 GB would work but leaves little room for the future.
  2. Storage: documents are small, so a 512 GB SSD is enough, and the SSD makes the computer feel fast.
  3. It stays on a counter, so a small desktop or all-in-one is fine; portability and battery do not matter. A webcam and microphone are needed for calls (built in on an all-in-one).
  4. 400 black-and-white pages a month makes cost per page important: choose a monochrome laser printer with duplex.
  5. Add an external drive for backups (see the backup lesson). Total cost of ownership matters more than the cheapest sticker price.

A small desktop or all-in-one with a 4 to 6 core CPU, 16 GB RAM and a 512 GB SSD, a webcam, a monochrome laser printer and an external backup drive, each chosen because of a specific bakery requirement.

Just for fun

Why did the laptop go to the eye doctor?

It was having trouble with its web sight. (Luckily it only needed new Windows.)

Hands-on activity

Be an IT consultant for someone you know

You need: a family member or friend willing to be interviewed, a computer with Python (or a free browser-based Python), and access to a store website or flyer.

  1. Interview your client with the six questions in Step 1. Write down their answers.
  2. Find the requirements for the two most demanding programs they use (search the program's name plus "system requirements").
  3. Pick three real computers within their budget. Copy the key specs.
  4. Choose 4 or 5 criteria and weights that fit this client, score each computer, and run the decision-matrix program with your numbers.
  5. Write a one-page recommendation: the computer, any peripherals, and a reason for each choice that refers to a requirement. Mention one thing you would not spend money on, and why.

What to look for: weights that clearly reflect the interview (a client who travels gives portability a high weight), specs that meet the recommended requirements, no obvious bottleneck, and reasons tied to requirements rather than "it's the best".

Your turn

1

What is the difference between minimum and recommended requirements?

2

A computer has a fast CPU, 16 GB of RAM and a 5400 rpm hard drive. Programs take a long time to open. What is the bottleneck?

3

Give three questions you would ask before recommending a computer.

4

In a decision matrix, Laptop X scores 4 for battery life and the weight is 3. How many points does it get?

5

Why should a recommendation consider ink or toner, not just the printer's price?

6

A Windows-only program must run. Why might a Chromebook be a poor choice?

More practice: warm-up

1

What is a bottleneck?

2

Which matters more to a student who carries a laptop all day: weight or GPU?

3

Name one spec that matters most for 3-D gaming.

4

What does total cost of ownership include?

5

In a decision matrix, what does the weight show?

More practice: on your own

1

Redo Maya's matrix for her brother, who games at home and never carries the computer. Use weights price 3, performance 5, portability 1, battery 1 and the same scores. Which wins?

2

A program lists "Recommended: 16 GB RAM, 4 GB VRAM". A laptop has 16 GB RAM and integrated graphics. Does it meet the recommended specs? Explain.

3

Explain why buying a top video card for a computer with 4 GB of RAM is a poor use of money.

4

Recommend peripherals for a person with low vision who writes reports.

5

In the decision-matrix program, which line would you change to make battery life the most important criterion?

Challenge

1

Using Maya's scores, can Desktop C ever win if every weight is a whole number from 1 to 5? Prove your answer. (Hint: subtract A's total from C's total, criterion by criterion.)

2

A user's budget is $1000. Option P: $900 laptop that meets recommended specs. Option Q: $700 laptop that meets only minimum specs, plus a $300 external SSD. Which would you recommend for a programmer who runs an IDE, a browser and a local database, and why?

3

Explain why two consultants could give different, but both good, recommendations for the same user.

Check your understanding

Quiz

1.

What should you do first when recommending a computer?

2.

A program's requirements say "Minimum: 8 GB RAM. Recommended: 16 GB RAM." A computer has 8 GB. What will most likely happen?

3.

A computer has a top CPU, top GPU and a slow hard drive, and it takes ages to load games. The hard drive is the...

4.

In a weighted decision matrix, a criterion has weight 4 and an option scores 3. How many points does that option get for it?

5.

For a user who prints 500 black-and-white pages a month, which printer spec matters most?

6.

Which recommendation is best justified?

For parents and teachers

Big idea: This lesson pulls together C1.1, C1.2 and C1.3: relating the specifications of internal components, the overall system and peripherals to what a real user needs. It also previews the requirements-gathering skills taught in the Software Development unit.

How to help: Volunteer to be the "client" for the activity, and answer honestly (including your budget). Ask your teen to justify every recommendation with one of your requirements. If your family is actually buying a computer, this is a perfect real task.

Common difficulties:

  • Recommending the most powerful option instead of the best fit.
  • Meeting only minimum requirements.
  • Ignoring bottlenecks: one weak part (often RAM or a hard drive) wastes the money spent elsewhere.
  • Weights that do not match the interview. Ask: "Why did you give that weight?"