TECHINTERACTIVES
FORGING IDEAS INTO REALITY
CLASS XI — COMPUTER SCIENCE (Code 083)
KVS Ernakulam Region | Session 2024–25 | 11SEE25CS03
COMPLETE STUDY MATERIAL
Unit-wise In-Depth Notes • All Question Types • Step-by-Step Answers
1M | 2M | 3M | 4M | 5M Questions Fully Solved
Prepared by
AKHILESH T.U
| +91 8891045887
TECH INTERACTIVES
IG Personal: @apparition_ace_3939 | Official: @the_tech_GuY_404
,UNIT 1: Computer Systems and Organisation (CSO)
Syllabus Marks: 10 Theory + 10 Practical | Total Periods: 20
■ 1.1 Basic Computer Organisation
A computer system is made up of hardware (physical components) and software (programs). Understanding their roles is
fundamental.
◆ Hardware vs Software
• Hardware: Physical parts you can touch — CPU, RAM, keyboard, monitor, HDD.
• Software: Instructions/programs — OS, browsers, games.
• Firmware: Software permanently stored in hardware (BIOS/UEFI).
◆ Input → Processing → Output → Storage Cycle
• Input: Data fed into computer via keyboard, mouse, scanner, microphone.
• Processing: CPU performs arithmetic & logic operations on the data.
• Output: Result displayed via monitor, printer, speaker.
• Storage: Data saved in RAM (temporary) or HDD/SSD (permanent).
◆ CPU — Central Processing Unit
• Brain of the computer. Divided into:
◦ ALU (Arithmetic Logic Unit): Performs +, -, *, /, comparisons.
◦ CU (Control Unit): Directs all operations, fetches/decodes instructions.
◦ Registers: Ultra-fast tiny memory inside CPU (e.g., Accumulator, PC, MAR, MDR).
◆ Memory — Units
Unit Full Form Value
Bit Binary Digit 0 or 1
Nibble — 4 bits
Byte — 8 bits
KB Kilobyte 1024 Bytes
MB Megabyte 1024 KB
GB Gigabyte 1024 MB
TB Terabyte 1024 GB
PB Petabyte 1024 TB
◆ Types of Memory
Primary Memory (Main Memory) — directly accessed by CPU
• RAM (Random Access Memory): Volatile — data lost when power off. Stores running programs.
• ROM (Read-Only Memory): Non-volatile — stores BIOS. Cannot be rewritten normally.
• Cache Memory: Fastest memory between CPU and RAM. L1, L2, L3 levels.
⚠COMMON MISTAKE: Hard Drive / SSD are SECONDARY storage, NOT primary. This is a frequent 1-mark MCQ trap!
Secondary Memory (Auxiliary Storage)
, • HDD (Hard Disk Drive): Magnetic, slow, cheap. 500 GB – 4 TB.
• SSD (Solid State Drive): Flash-based, fast, expensive. Replacing HDDs.
• USB Drives, CD/DVD, Blu-ray: Portable/optical storage.
📝 NOTE: Primary storage is directly accessible by CPU. Secondary needs I/O channels.
★ 1-Mark Questions — Computer Organisation
Q (1M): Which of the following is NOT a primary storage device? a) RAM b) ROM c) Hard Drive d) Cache
✔ ANSWER: (c) Hard Drive
Explanation: Hard Drive is SECONDARY storage. RAM, ROM and Cache are all primary storage directly accessible by the CPU.
Q (1M): The full form of ALU is:
✔ ANSWER: Arithmetic Logic Unit
Explanation: ALU performs all arithmetic operations (+,-,*,/) and logical comparisons (>,<,==). It is a sub-unit of the CPU.
Q (1M): Which memory is volatile? a) ROM b) RAM c) Cache d) Both b and c
✔ ANSWER: (d) Both RAM and Cache are volatile
Explanation: Volatile memory loses data when power is switched off. RAM and Cache are volatile. ROM is non-volatile.
■ 1.2 Types of Software
◆ System Software
• Manages hardware and provides platform for application software.
• Operating System (OS): Windows, Linux, macOS, Android.
• Device Drivers: Interface between hardware devices and OS.
• Utilities: Antivirus, disk cleanup, file compression.
◆ Language Translators
Translator How it works Example
Compiler Translates ENTIRE program at once; shows ALL errors GCC (C), javac (Java)
together; faster execution
Interpreter Translates and executes ONE LINE at a time; stops at Python, Ruby
first error; slower
Assembler Converts Assembly language → Machine code NASM, MASM
◆ Application Software
• Performs specific tasks for the user.
• General Purpose: MS Word, Excel, VLC, Chrome.
• Specific Purpose: Banking software, hospital management systems.
★ 2-Mark Question
Q (2M): Differentiate between Compiler and Interpreter.
Compiler vs Interpreter — Key Differences:
Aspect Compiler Interpreter
Translation Entire program at once Line by line
Error Reporting Reports ALL errors after full scan Stops at FIRST error
Speed Faster (pre-compiled) Slower (translates each run)
, Output Creates executable file No separate executable
Example GCC, javac Python, Ruby
■ 1.3 Operating System (OS)
◆ Functions of OS
• Process Management: Schedules CPU time among running programs.
• Memory Management: Allocates/deallocates RAM to processes.
• File Management: Organises files/folders; manages permissions.
• Device Management: Controls I/O devices via drivers.
• User Interface: Provides CLI (Command Line) or GUI (Graphical).
• Security: Authentication, access control.
◆ OS User Interface
• CLI (Command Line Interface): User types text commands. Eg: Linux terminal, CMD.
• GUI (Graphical User Interface): Icons, windows, mouse-driven. Eg: Windows 11, macOS.
■ 1.4 Number Systems
System Base Digits Used Example
Binary 2 0, 1 1010₂
Octal 8 0–7 12₈
Decimal 10 0–9 25₁₀
Hexadecimal 16 0–9, A–F 1A₁₆
◆ Decimal → Binary Conversion
Method: Divide by 2, collect remainders bottom-to-top.
Example: Convert 25₁₀ to binary
25 ÷ 2 = 12 rem 1 ↑
12 ÷ 2 = 6 rem 0 |
6 ÷ 2 = 3 rem 0 |
3 ÷ 2 = 1 rem 1 |
1 ÷ 2 = 0 rem 1 | Read upwards
Result: 11001₂
✔ ANSWER: 25₁₀ = 11001₂
◆ Binary → Decimal Conversion
Method: Multiply each bit by 2 raised to its positional power, sum up.
1 1 0 0 1 (binary)
↓ ↓ ↓ ↓ ↓
1×2⁴ + 1×2³ + 0×2² + 0×2¹ + 1×2⁰
= 16 + 8 + 0 + 0 + 1
= 25₁₀
◆ Decimal → Octal Conversion
Method: Divide by 8, collect remainders bottom-to-top.
FORGING IDEAS INTO REALITY
CLASS XI — COMPUTER SCIENCE (Code 083)
KVS Ernakulam Region | Session 2024–25 | 11SEE25CS03
COMPLETE STUDY MATERIAL
Unit-wise In-Depth Notes • All Question Types • Step-by-Step Answers
1M | 2M | 3M | 4M | 5M Questions Fully Solved
Prepared by
AKHILESH T.U
| +91 8891045887
TECH INTERACTIVES
IG Personal: @apparition_ace_3939 | Official: @the_tech_GuY_404
,UNIT 1: Computer Systems and Organisation (CSO)
Syllabus Marks: 10 Theory + 10 Practical | Total Periods: 20
■ 1.1 Basic Computer Organisation
A computer system is made up of hardware (physical components) and software (programs). Understanding their roles is
fundamental.
◆ Hardware vs Software
• Hardware: Physical parts you can touch — CPU, RAM, keyboard, monitor, HDD.
• Software: Instructions/programs — OS, browsers, games.
• Firmware: Software permanently stored in hardware (BIOS/UEFI).
◆ Input → Processing → Output → Storage Cycle
• Input: Data fed into computer via keyboard, mouse, scanner, microphone.
• Processing: CPU performs arithmetic & logic operations on the data.
• Output: Result displayed via monitor, printer, speaker.
• Storage: Data saved in RAM (temporary) or HDD/SSD (permanent).
◆ CPU — Central Processing Unit
• Brain of the computer. Divided into:
◦ ALU (Arithmetic Logic Unit): Performs +, -, *, /, comparisons.
◦ CU (Control Unit): Directs all operations, fetches/decodes instructions.
◦ Registers: Ultra-fast tiny memory inside CPU (e.g., Accumulator, PC, MAR, MDR).
◆ Memory — Units
Unit Full Form Value
Bit Binary Digit 0 or 1
Nibble — 4 bits
Byte — 8 bits
KB Kilobyte 1024 Bytes
MB Megabyte 1024 KB
GB Gigabyte 1024 MB
TB Terabyte 1024 GB
PB Petabyte 1024 TB
◆ Types of Memory
Primary Memory (Main Memory) — directly accessed by CPU
• RAM (Random Access Memory): Volatile — data lost when power off. Stores running programs.
• ROM (Read-Only Memory): Non-volatile — stores BIOS. Cannot be rewritten normally.
• Cache Memory: Fastest memory between CPU and RAM. L1, L2, L3 levels.
⚠COMMON MISTAKE: Hard Drive / SSD are SECONDARY storage, NOT primary. This is a frequent 1-mark MCQ trap!
Secondary Memory (Auxiliary Storage)
, • HDD (Hard Disk Drive): Magnetic, slow, cheap. 500 GB – 4 TB.
• SSD (Solid State Drive): Flash-based, fast, expensive. Replacing HDDs.
• USB Drives, CD/DVD, Blu-ray: Portable/optical storage.
📝 NOTE: Primary storage is directly accessible by CPU. Secondary needs I/O channels.
★ 1-Mark Questions — Computer Organisation
Q (1M): Which of the following is NOT a primary storage device? a) RAM b) ROM c) Hard Drive d) Cache
✔ ANSWER: (c) Hard Drive
Explanation: Hard Drive is SECONDARY storage. RAM, ROM and Cache are all primary storage directly accessible by the CPU.
Q (1M): The full form of ALU is:
✔ ANSWER: Arithmetic Logic Unit
Explanation: ALU performs all arithmetic operations (+,-,*,/) and logical comparisons (>,<,==). It is a sub-unit of the CPU.
Q (1M): Which memory is volatile? a) ROM b) RAM c) Cache d) Both b and c
✔ ANSWER: (d) Both RAM and Cache are volatile
Explanation: Volatile memory loses data when power is switched off. RAM and Cache are volatile. ROM is non-volatile.
■ 1.2 Types of Software
◆ System Software
• Manages hardware and provides platform for application software.
• Operating System (OS): Windows, Linux, macOS, Android.
• Device Drivers: Interface between hardware devices and OS.
• Utilities: Antivirus, disk cleanup, file compression.
◆ Language Translators
Translator How it works Example
Compiler Translates ENTIRE program at once; shows ALL errors GCC (C), javac (Java)
together; faster execution
Interpreter Translates and executes ONE LINE at a time; stops at Python, Ruby
first error; slower
Assembler Converts Assembly language → Machine code NASM, MASM
◆ Application Software
• Performs specific tasks for the user.
• General Purpose: MS Word, Excel, VLC, Chrome.
• Specific Purpose: Banking software, hospital management systems.
★ 2-Mark Question
Q (2M): Differentiate between Compiler and Interpreter.
Compiler vs Interpreter — Key Differences:
Aspect Compiler Interpreter
Translation Entire program at once Line by line
Error Reporting Reports ALL errors after full scan Stops at FIRST error
Speed Faster (pre-compiled) Slower (translates each run)
, Output Creates executable file No separate executable
Example GCC, javac Python, Ruby
■ 1.3 Operating System (OS)
◆ Functions of OS
• Process Management: Schedules CPU time among running programs.
• Memory Management: Allocates/deallocates RAM to processes.
• File Management: Organises files/folders; manages permissions.
• Device Management: Controls I/O devices via drivers.
• User Interface: Provides CLI (Command Line) or GUI (Graphical).
• Security: Authentication, access control.
◆ OS User Interface
• CLI (Command Line Interface): User types text commands. Eg: Linux terminal, CMD.
• GUI (Graphical User Interface): Icons, windows, mouse-driven. Eg: Windows 11, macOS.
■ 1.4 Number Systems
System Base Digits Used Example
Binary 2 0, 1 1010₂
Octal 8 0–7 12₈
Decimal 10 0–9 25₁₀
Hexadecimal 16 0–9, A–F 1A₁₆
◆ Decimal → Binary Conversion
Method: Divide by 2, collect remainders bottom-to-top.
Example: Convert 25₁₀ to binary
25 ÷ 2 = 12 rem 1 ↑
12 ÷ 2 = 6 rem 0 |
6 ÷ 2 = 3 rem 0 |
3 ÷ 2 = 1 rem 1 |
1 ÷ 2 = 0 rem 1 | Read upwards
Result: 11001₂
✔ ANSWER: 25₁₀ = 11001₂
◆ Binary → Decimal Conversion
Method: Multiply each bit by 2 raised to its positional power, sum up.
1 1 0 0 1 (binary)
↓ ↓ ↓ ↓ ↓
1×2⁴ + 1×2³ + 0×2² + 0×2¹ + 1×2⁰
= 16 + 8 + 0 + 0 + 1
= 25₁₀
◆ Decimal → Octal Conversion
Method: Divide by 8, collect remainders bottom-to-top.
