हिंदी में: कंप्यूटर क्या है, हार्डवेयर-सॉफ़्टवेयर कैसे साथ काम करते हैं और मेमोरी के प्रकार — CSE की पहली सीढ़ी।
What is a computer?
A computer is an electronic machine that accepts data (input), processes it according to a set of instructions (a program), stores data and produces results (output). Every computer — from a smartphone to a cloud server — follows this same basic idea, known as the Input → Process → Output (IPO) cycle, with storage supporting each step.
Most modern computers follow the von Neumann architecture, in which program instructions and data are stored in the same memory and the CPU fetches them one after another.
Main parts of a computer system
| Part | Role | Examples |
|---|---|---|
| Input devices | Send data and commands to the computer | Keyboard, mouse, touchscreen, scanner, microphone |
| CPU (processor) | Executes instructions | Intel Core, AMD Ryzen, ARM chips in phones |
| Primary memory | Holds data and programs currently in use | RAM, cache, ROM |
| Secondary storage | Keeps data permanently | SSD, HDD, pen drive, memory card |
| Output devices | Show or deliver results | Monitor, printer, speakers |
Inside the CPU
- ALU (Arithmetic Logic Unit) – performs arithmetic (+, −, ×, ÷) and logical operations (AND, OR, NOT, comparisons).
- Control Unit (CU) – directs the flow of data and tells other parts what to do.
- Registers – very small, very fast storage locations inside the CPU (for example the Program Counter and the Accumulator).
Hardware vs software
- Hardware is the physical part you can touch.
- Software is the set of programs that tells hardware what to do.
- System software – operating systems (Windows, Linux, Android), device drivers, utilities.
- Application software – browsers, word processors, games, mobile apps.
- Programming tools – compilers, interpreters, assemblers, IDEs.
Memory hierarchy
Memory is organised as a pyramid: the closer it is to the CPU, the faster, smaller and costlier it is.
- Registers (fastest, a few bytes)
- Cache memory (L1, L2, L3)
- Main memory – RAM (volatile: contents are lost when power is off)
- Secondary storage – SSD / HDD (non-volatile)
- Tertiary / backup storage – tape, cloud archives (slowest, cheapest per GB)
ROM (Read-Only Memory) is non-volatile and stores firmware such as the BIOS/UEFI that starts the computer.
Units of data
| Unit | Size |
|---|---|
| Bit | 0 or 1 |
| Nibble | 4 bits |
| Byte | 8 bits |
| Kilobyte (KB) | 1024 bytes |
| Megabyte (MB) | 1024 KB |
| Gigabyte (GB) | 1024 MB |
| Terabyte (TB) | 1024 GB |
Storage manufacturers often use decimal units (1 KB = 1000 bytes), which is why a “1 TB” drive shows a little less space in the operating system. The binary units are formally called KiB, MiB, GiB.
Types of computers
- Supercomputers – used for weather forecasting, scientific simulation (India’s PARAM series is an example).
- Mainframes – large systems for banks and railways that handle huge numbers of transactions.
- Servers – provide services such as websites, email and databases to other computers.
- Personal computers – desktops and laptops.
- Mobile and embedded computers – smartphones, smart TVs, washing machines, cars.
Generations of computers (overview)
| Generation | Key technology |
|---|---|
| First | Vacuum tubes |
| Second | Transistors |
| Third | Integrated circuits (ICs) |
| Fourth | Microprocessors (VLSI) |
| Fifth | AI-oriented, parallel and highly integrated systems |
Quick revision
- IPO cycle: Input → Process → Output, with storage.
- CPU = ALU + Control Unit + registers.
- RAM is volatile; ROM, SSD and HDD are non-volatile.
- 1 byte = 8 bits.
- System software manages the computer; application software helps the user do tasks.