Class 9 Computer Important Questions with Answers (Long answers)

A computer takes data through input devices (keyboard, mouse, scanner, mic). The CPU’s control unit and ALU process it using registers and cache. RAM holds working data; ROM holds start-up code. Results go to output devices (monitor, printer, speaker). Secondary storage keeps files after shutdown. UPS protects the process from sudden power loss. Class 9 answers should name parts and the direction of data, not invent extra chips. Example: typing an essay (input), editing in RAM (process), saving on disk (storage), printing (output).

Software is a set of instructions. System software includes the OS, device drivers and utilities such as backup or antivirus. Application software includes Word, Excel, PowerPoint, browsers and educational apps. Programming tools (editors, compilers) help create new software. Licences matter: use genuine Office, Linux, or approved freeware/open source — not pirated disks. Firmware on devices is software stored in chips. Students should classify a given name (Chrome vs Windows vs driver) in exams.

The OS loads at boot and then manages processes so Word and a browser can both open. It allocates RAM, keeps files in folders, talks to printers through drivers, and provides a GUI. It also checks login passwords. Recycle Bin, Task Manager and file permissions are everyday OS services on Windows labs; Linux labs use a desktop plus terminal. Do not treat a browser as an OS. Versions in school are real ones (e.g. Windows 10/11), not imaginary Windows 12.

Bit → nibble (4) → byte (8) → KB → MB → GB → TB, each step ×1024 after byte. Example: 2 GB = 2×1024 MB = 2048 MB = 2048×1024 KB. Another: a 512 MB file is 512/1024 GB = 0.5 GB. RAM is primary and volatile; a 4 GB pen drive is secondary. Cache sits between CPU and RAM for speed. Exam answers must show the factor 1024, not silent 1000, unless the question says SI units.

Input: keyboard, mouse, scanner, mic, webcam, joystick, barcode reader. Output: monitor, speaker, printer, projector, plotter, Braille embosser. Some devices are both (touchscreen). In a classroom, the teacher laptop (input+process) sends HDMI output to a projector; students type on lab keyboards; a shared laser printer makes hard copies. Soft copy is on screen; print only when needed. Drivers and correct ports (USB, HDMI) complete the chain.

A school lab LAN uses switches, Ethernet cables or Wi-Fi, and private IP addresses so PCs can share a printer and files. A router connects that LAN to the internet, which is a WAN of many networks. MAN is city-scale. Modem links to the ISP. Fibre and radio are media; bandwidth and latency describe quality. Students should draw a simple diagram: PCs–switch–router–internet. Do not confuse IP address with email address.

Email needs a correct To address, a subject, a clear body and careful attachments. CC shows copies; BCC hides receivers. The web uses browsers, URLs and HTTP/HTTPS. Search engines help but results must be judged. Spam and phishing hide in both mail and web. Netiquette: no caps-shouting, no rumour forwards. WWW is not the whole internet. Practical: save school work offline too, because the link can fail.

Title idea: Think before you click. Cover passwords, OTP, phishing, cyberbullying, public Wi-Fi, software updates, privacy of photos, and digital footprints. Give actions: lock screens, report bullying with evidence, ignore unknown .exe files, use two-factor where the school provides it. Mention that firewalls and antivirus help but cannot replace common sense. End with the helpline culture: tell a trusted adult the same day. No need for scary invented viruses; real habits matter.

Word: edit a notice, apply fonts, bullets, header, page setup, mail merge, shortcuts Ctrl+S/B/C/V. Excel: enter a mark list, =SUM, average, simple IF if taught, make a column chart, freeze header row. PowerPoint: 5–6 slides on a lesson, readable font, F5, slide sorter. Common errors: forgetting = in Excel, too much text on a slide, not saving. Mention file extensions .docx .xlsx .pptx so the OS opens the right app.

Decimal to binary: divide by 2, list remainders upwards. 13 → 1101; 8 → 1000. Binary to decimal: add powers of two where bits are 1. 10110 → 16+4+2 = 22; 101 → 4+1 = 5. Also state 1 byte = 8 bits = 256 values. Mention ASCII as character coding. Show working in a table of weights 16 8 4 2 1. Neat steps score more than the final digit alone.

IPR protects creations. Copyright covers original writing, music and code expression; you may quote a little for study with credit, not upload a whole book. Plagiarism is academic theft — rewrite and cite. Trademarks protect logos; patents are for inventions at a legal level. Freeware is free to use as allowed; open source shares source under rules; pirated paid software is illegal and often unsafe. Creative Commons explains sharing. A project bibliography is part of the marks and of ethics.

Keep liquids away, do not eat at the keyboard, use UPS/stabiliser if provided, do not block CPU fans, insert USB carefully, shut down before unplugging, cover webcams for privacy, report loose sockets to the teacher. Dust and humidity harm ports. Pendrives should be scanned. These are maintenance habits, not extra theory chips. Good care is cheaper than a new machine.

Freeware: no price, source may be closed (a free PDF reader). Shareware: trial then pay if you continue. Open source: source available under a licence (many Linux tools). Custom: written for one school or office. All four can be legal; piracy is a fifth illegal path. Choose by need, licence and teacher approval. Price zero does not mean you may claim you wrote it.

A file is a named collection of data; a folder groups files. The extension (.docx, .jpg) hints the format. Paths such as C:\Class9\science.docx locate them on Windows-style disks. Delete sends many files to Recycle Bin; empty it to free space. Backup copies to another drive or trusted cloud save you from disk failure or ransomware. OS permissions stop others from casually erasing your work. Save every few minutes.

HDD: large, cheaper per GB, moving parts, slower, used as main disk in older desktops. SSD: faster, no spinning platter, common in newer laptops, costs more per GB. Pen drive: portable flash for submitting practicals; easy to lose or infect. All are secondary storage. Do not keep the only copy of a board project on one cheap pen drive. Eject safely to avoid file corruption.

In client-server, a central server holds accounts, files or the website; labs are clients. In P2P, PCs share folders as equals — simple but harder to control. Schools prefer server + teacher admin for updates and restrictions. The internet itself is many servers (web, mail) and millions of clients (browsers). Draw both as box diagrams in long answers.

The browser reads the protocol and domain. DNS finds an IP address. A request goes over the LAN/router/internet using TCP/IP. The web server returns a page over HTTP/HTTPS. The browser renders HTML and may store cookies. If HTTPS, data is encrypted on the way. Errors can be a wrong URL, no DNS, or no cable/Wi-Fi. This story is enough; no need for vendor packet captures.

A photo of a classmate is their personal data — ask before posting. Location tags can show home and school timings. Passwords and OTP are keys; never dictate them. Consent can be withdrawn; delete if asked. Apps ask for camera/mic — allow only if needed. Law and school rules both apply. Long answers should give do’s and don’ts, not scare stories about fictional OS versions.

A formula starts with = and can use + − * /. Functions such as SUM, AVERAGE, MAX, MIN take ranges: =AVERAGE(B2:B31). Cell references change when you fill down if they are relative. Make a bar chart of subject averages. Freeze the header. Common error: typing SUM(A1:A5) without =. Save as .xlsx. This is the usual Class 9 practical pattern.

Decimal base 10 (0–9) is daily life. Binary base 2 (0,1) is machine language of bits. Octal base 8 (0–7) and hexadecimal base 16 (0–9,A–F) shorten long binary (each hex digit is 4 bits). Convert using division or place values. Example: decimal 15 is 1111 binary and F hex. Class 9 may only require binary–decimal; mention others if the syllabus lists them.