Ch 1 of Class 11 CS covers the complete computer system — functional components of a CPU, memory hierarchy, input/output devices, and software classification.
CPU components: ALU (arithmetic & logical operations), CU (fetch-decode-execute cycle), Registers (instruction register, program counter, accumulator), Cache (L1, L2, L3 — bridge between CPU and RAM). Memory hierarchy (speed vs capacity): Registers > Cache > RAM > Secondary storage. RAM: SRAM (cache, faster, expensive) and DRAM (main memory, slower, cheaper). ROM types: PROM, EPROM, EEPROM. Secondary: HDD (magnetic), SSD (flash, faster, no moving parts), optical (CD/DVD/Blu-ray), flash drives.
System software: manages hardware. OS (process management, memory management, file system, device drivers), language processors (compiler: entire source → machine code; interpreter: line by line; assembler: assembly → machine), utility software (antivirus, disk tools, backup). Application software: general-purpose (MS Office, browsers) and specific-purpose (accounting, hospital management). Open source: free, source code available (Linux, Python, LibreOffice). Proprietary: paid, closed source (Windows, MS Office).
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SRAM (Static RAM): uses flip-flop circuits, retains data as long as power is on without refresh, faster, more expensive, used for CPU cache. DRAM (Dynamic RAM): uses capacitors that leak charge, needs periodic refresh (thousands of times per second), slower but cheaper and higher density, used for main memory (the "RAM" in your computer specs). SRAM: ~1-10 ns access, expensive. DRAM: ~50-70 ns access, affordable in large capacities.
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