Revision Notes for Class 9 Computer Science: All Chapters
Review targeted revision notes for Class 9 Computer Science with the CBSE Class 9 Computer Applications Computer System Notes with Questions and Answers Set 01. Built according to official educational guidelines for the 2026-27 academic year, these downloadable summaries for All Chapters support daily study and last-minute exam readiness.
Review All Chapters for Class 9 Computer Science
View or download the dedicated All Chapters revision resource below. Engaging with these structured concept notes daily ensures continuous academic progress and mastery of the 2026-27 curriculum for Computer Science.
The Computer
A computer is a programmable electronic device that accepts and stores input, processes the data according to a set of instructions and gives meaningful output. Its characteristics are speed, accuracy, reliability, storage capacity and versatility. A computer follows the IPO cycle: input, process, output. It is used in the military, banks, hospitals, media, communication, railways, airlines and many other fields.
Organisation of a Computer
The basic organisation is an input unit, the CPU and an output unit. The CPU has three parts: the memory unit (MU), the arithmetic logic unit (ALU) and the control unit (CU). The speed of a processor depends on the number of instructions it executes per second and is measured in megahertz (MHz).
Memory
| Memory | Details |
|---|---|
| Internal (primary) memory | Stores data and programs being executed; limited capacity. Includes RAM and ROM |
| RAM | Volatile; stores application programs; can be read and written |
| ROM | Non-volatile (permanent); stores start-up instructions; can only be read |
| Cache memory | Special high-speed memory holding frequently used instructions so the CPU can reach them quickly |
| External (secondary) memory | Stores large amounts of data permanently; slower than internal memory |
The smallest unit of memory is the bit (0 or 1). Larger units are nibble, byte, KB, MB, GB, TB and PB.
Types of Computers
| Basis | Types |
|---|---|
| Principle of operation | Analog, digital and hybrid computers |
| Size and capacity | Microcomputers, minicomputers, mainframe computers and supercomputers |
Questions and Answers
1. Fill in: Read only memory is a part of ___ memory. A computer has ___ IQ. The speed of the CPU depends on the number of ___ executed per second. The speed of external memory is ___ than internal memory. The speed of the CPU is measured in ___.
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Answer: internal; zero; instructions; slower; MHz
Teacher's Note: Use the key term in your answer.
2. Name the three components of the CPU.
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Answer: Memory unit, control unit and arithmetic logic unit.
Teacher's Note: Give an example if the question allows.
3. What is a computer?
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Answer: A programmable electronic device that accepts input, processes data according to instructions and gives meaningful output.
Teacher's Note: Write a short, clear answer.
4. What is the difference between RAM and ROM?
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Answer:
| RAM | ROM |
|---|---|
| Volatile, temporary | Non-volatile, permanent |
| Can be read and written | Can only be read |
| Stores application programs | Stores the start-up program |
Teacher's Note: Remember this for your exam.
5. What is the need for secondary memory?
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Answer: The main memory is temporary, expensive and limited, so secondary memory is used to store large amounts of data and instructions permanently.
Teacher's Note: Learn this point and write it in your own words.
6. Write the full forms: PROM, EPROM, EEPROM, SRAM, DRAM, BIOS.
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Answer: Programmable Read Only Memory; Erasable Programmable Read Only Memory; Electrically Erasable Programmable Read Only Memory; Static Random Access Memory; Dynamic Random Access Memory; Basic Input Output System.
Teacher's Note: Use the key term in your answer.
7. Write short notes on blog and wiki.
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Answer: A blog (from 'weblog') is an easy-to-create website where a person posts dated entries and shares thoughts; readers can comment. A wiki is a collaborative website whose content users can add or modify directly from the browser.
Teacher's Note: Give an example if the question allows.
8. Write two characteristics and two limitations of a computer.
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Answer: Characteristics: speed and accuracy. Limitations: dependence on power and no intelligence of its own.
Teacher's Note: Write a short, clear answer.
9. What is a CPU? Explain its parts.
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Answer: The CPU is the main unit that controls all devices and does arithmetic and logical operations. The memory unit is the main storage, the ALU does arithmetic and logical operations, and the control unit controls the working of the other parts.
Teacher's Note: Remember this for your exam.
10. What is meant by 'computers work diligently'?
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Answer: A computer completes every task without a break and does not get tired.
Teacher's Note: Learn this point and write it in your own words.
11. Which is the most powerful category of computers?
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Answer: Supercomputers, the fastest and most expensive computers, which process trillions of instructions per second.
Teacher's Note: Use the key term in your answer.
12. Give three examples each of input and output devices.
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Answer: Input: keyboard, mouse, scanner. Output: monitor, printer, speakers.
Teacher's Note: Give an example if the question allows.
13. What is a newsgroup?
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Answer: A discussion platform on a particular subject, where messages are posted to a central site and distributed over Usenet.
Teacher's Note: Write a short, clear answer.
Download CBSE Revision Notes: Class 9 Computer Science All Chapters
Key Concepts and Summary for Class 9 Computer Science All Chapters
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NCERT-Aligned Chapter Summary and Notes
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FAQs
You can download the teacher prepared revision notes for CBSE Class 9 Computer Applications Computer System Notes with Questions and Answers Set 01 from StudiesToday.com. These notes are designed as per 2026-27 academic session to help Class 9 students get the best study material for Computer Science.
Yes, our CBSE Class 9 Computer Applications Computer System Notes with Questions and Answers Set 01 include 50% competency-based questions with focus on core logic, keyword definitions, and the practical application of Computer Science principles which is important for getting more marks in 2026 CBSE exams.
Yes, our CBSE Class 9 Computer Applications Computer System Notes with Questions and Answers Set 01 provide a detailed, topic wise breakdown of the chapter. Fundamental definitions, complex numerical formulas and all topics of CBSE syllabus in Class 9 is covered.
These notes for Computer Science are organized into bullet points and easy-to-read charts. By using CBSE Class 9 Computer Applications Computer System Notes with Questions and Answers Set 01, Class 9 students fast revise formulas, key definitions before the exams.
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