Search engines and how they find information in Intro to Computing - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a search engine?

A search engine is a tool that helps you find information on the internet by looking through many web pages and showing you the most relevant results.

beginner

What does a web crawler (or spider) do in a search engine?

A web crawler visits web pages on the internet, reads their content, and follows links to find more pages. It collects information to help the search engine know what is on each page.

intermediate

Explain the role of an index in a search engine.

An index is like a giant library catalog for the internet. It stores information about web pages so the search engine can quickly find pages that match your search words.

intermediate

How does a search engine decide which results to show first?

The search engine uses algorithms to rank pages based on factors like how often your search words appear, how trustworthy the page is, and how many other pages link to it.

beginner

What is the basic flow of how a search engine finds and shows information?

1. The web crawler finds and reads web pages.
2. The index stores information about these pages.
3. When you search, the engine looks in the index.
4. It ranks pages by relevance.
5. It shows you the best results.

What is the first step a search engine takes to find information on the web?

A Using a web crawler to visit pages

B Showing search results to the user

C Ranking pages by popularity

D Storing user search history

The search engine starts by using a web crawler to visit and read web pages.

What is the purpose of the index in a search engine?

A To write new web pages

B To store information about web pages for quick searching

C To delete old web pages

D To display ads to users

The index acts like a catalog that helps the search engine find pages quickly.

Which factor does NOT usually affect how a search engine ranks pages?

A How many times your search words appear on the page

B How many other pages link to the page

C The color scheme of the web page

D How trustworthy the page is

The color scheme does not affect ranking; content and links do.

What is a web crawler also called?

A Spider

B Browser

C Server

D Firewall

A web crawler is often called a spider because it 'crawls' the web like a spider.

After the search engine looks in the index, what does it do next?

A Updates the web crawler

B Deletes the pages

C Sends an email to the user

D Ranks the pages by relevance

The search engine ranks pages to show the most relevant results first.

Describe the main steps a search engine uses to find and show information from the web.

Think about how the search engine reads pages, remembers them, and then finds the best matches for your search.

Explain why a search engine uses an index instead of searching the whole web every time you search.

Imagine looking for a book in a huge library without a catalog.

Practice

1. What is the main role of a search engine crawler?

easy

A. To display search results to users

B. To organize information into categories

C. To visit web pages and collect information

D. To delete outdated web pages from the internet

Solution

1. Step 1: Understand the crawler's function

   A crawler is a program that visits many web pages to gather data.

2. Step 2: Differentiate from other parts

   Unlike indexers or searchers, crawlers focus on collecting information, not organizing or displaying it.

3. Final Answer:

   To visit web pages and collect information -> Option C

4. Quick Check:

   Crawler = Collects data [OK]

Hint: Crawlers collect data by visiting pages [OK]

Common Mistakes:

• Confusing crawlers with indexers
• Thinking crawlers display results
• Assuming crawlers delete pages

2. Which of the following is the correct order of steps a search engine uses to find information?

easy

A. Indexing -> Crawling -> Searching

B. Searching -> Crawling -> Indexing

C. Searching -> Indexing -> Crawling

D. Crawling -> Indexing -> Searching

Solution

1. Step 1: Recall the search engine process

   First, the crawler visits pages (Crawling), then the data is organized (Indexing), and finally results are shown (Searching).

2. Step 2: Match the correct sequence

   Only Crawling -> Indexing -> Searching lists the steps in the correct order.

3. Final Answer:

   Crawling -> Indexing -> Searching -> Option D

4. Quick Check:

   Process order = Crawling, Indexing, Searching [OK]

Hint: Remember: Crawl first, then index, then search [OK]

Common Mistakes:

• Mixing up the order of steps
• Thinking searching happens before indexing
• Assuming indexing happens before crawling

3. Consider this simplified flowchart of a search engine process:



What happens immediately after the search query is received?

medium

A. The search engine shows the results

B. The search engine indexes the data

C. The search engine crawls new web pages

D. The search engine deletes old data

Solution

1. Step 1: Analyze the flowchart sequence

   The flowchart shows the steps: Crawl -> Index -> Search Query -> Show Results.

2. Step 2: Identify the step after receiving the search query

   After the search query, the next step is to show the results to the user.

3. Final Answer:

   The search engine shows the results -> Option A

4. Quick Check:

   After query = Show results [OK]

Hint: After query input, results are displayed [OK]

Common Mistakes:

• Thinking crawling happens after query
• Confusing indexing with showing results
• Assuming data deletion occurs here

4. A student wrote this description of how search engines work:

"Search engines first show results, then crawl web pages, and finally index the data."

What is wrong with this description?

medium

A. Crawling happens after indexing

B. The order of steps is incorrect

C. Search engines do not index data

D. Search engines delete data before crawling

Solution

1. Step 1: Review the correct order of search engine steps

   The correct order is crawling first, then indexing, and finally showing results.

2. Step 2: Compare with the student's description

   The student says results are shown first, which is incorrect.

3. Final Answer:

   The order of steps is incorrect -> Option B

4. Quick Check:

   Correct order ≠ student's order [OK]

Hint: Remember: Crawl -> Index -> Show results [OK]

Common Mistakes:

• Believing results show before crawling
• Thinking indexing is optional
• Assuming data deletion is part of the main steps

5. Imagine a search engine that only crawls web pages but never indexes the data. What problem would users face when searching?

hard

A. Users would get no search results or irrelevant ones

B. Search results would be slow but accurate

C. The search engine would delete all web pages

D. Users would see only images, not text

Solution

1. Step 1: Understand the role of indexing

   Indexing organizes and stores data so the search engine can quickly find relevant results.

2. Step 2: Consider the effect of missing indexing

   Without indexing, the search engine cannot match queries to relevant pages, so users get no or irrelevant results.

3. Final Answer:

   Users would get no search results or irrelevant ones -> Option A

4. Quick Check:

   No indexing = no relevant results [OK]

Hint: No indexing means no useful search results [OK]

Common Mistakes:

• Thinking results would still be accurate
• Assuming crawling deletes pages
• Believing search shows only images