Operating system

foundation

Isse pehle ki hum 'Operating System' samjhein, hume 2 basic cheezein clear karni hongi — Hardware kya hota hai aur Software kya hota hai. Agar ye foundation clear hai to aage sab kuch easily samajh aayega.

1. Computer System ke 4 Main Components

• Hardware — physical parts jo tum touch kar sakte ho: CPU (processor), RAM (memory), Hard Disk/SSD, Keyboard, Mouse, Monitor, Printer, Network card.

• Operating System — hardware ko control karne wala main software (Windows, Linux, Android, etc.)

• Application Programs — jo software user directly use karta hai kaam karne ke liye (Word, Chrome, Games, WhatsApp).

• Users — insaan jo computer use karte hain, ya doosre computers/programs jo requests bhejte hain.

  +-----------------------------------+

  |          USERS (People)            |

  +-----------------------------------+

  |  Application Programs               |   <- Word, Chrome, Games

  |  (Compilers, Browsers, etc.)        |

  +-----------------------------------+

  |       OPERATING SYSTEM              |   <- Windows, Linux, Android

  +-----------------------------------+

  |  Hardware (CPU, RAM, Disk...)       |

  +-----------------------------------+

Is layered diagram se samajh aata hai ki OS beech mein baithkar hardware ko chhupata hai aur upar wale layers (applications, users) ko simple interface deta hai. Ye concept baar baar use hoga aage.

2. Kyun zaroorat padi OS ki?

• Socho agar OS na ho, to har application programmer ko khud hi likhna padega ki:

  • Disk se data kaise physically read/write karna hai (sectors, tracks ka calculation)

  • Keyboard se key press kaise detect karni hai (hardware signals)

  • Printer ko kaise commands bhejni hain

  • Agar 2 programs ek saath CPU maangein to kisko pehle dena hai

Ye sab bohot complex aur repetitive kaam hai. Agar har application ye khud kare to development bohot slow aur error-prone ho jayega. Isliye OS ye saara complex, common kaam ek baar karta hai, aur applications ko simple functions (system calls) deta hai use karne ke liye — jaise 'file open karo', 'print karo'. Isko hum kehte hain OS abstraction deta hai.

1. Operating System ki Definition

OS ki koi single, universally-fixed definition nahi hai — kyunki OS bohot saare kaam karta hai. Lekin standard textbooks (jaise Silberschatz) 3 alag angles se define karte hain:

Definition 1 — Resource Manager ke roop mein

"Operating System ek software hai jo computer ke hardware resources (CPU, memory, I/O devices, files) ko manage karta hai, aur unko different programs/users ke beech is tarah allocate karta hai ki system efficiently aur fairly chale."

Is view mein OS ek 'referee' ya 'manager' hai — jaise ek traffic police jo decide karta hai kaunsi gaadi kab road use karegi, taaki accidents (conflicts) na ho aur traffic (system) smoothly chale.

Definition 2 — Extended/Virtual Machine ke roop mein

"OS hardware ki complexity ko chhupa kar user/programmer ko ek simple, convenient, 'extended machine' ka view deta hai, jisse actual hardware se kaam karna easy ho jaye."

Yaani jab tum file save karte ho, tumhe pata nahi hota ki disk pe physically kahan bytes likhi ja rahi hain — tumhe bas ek simple command deta hai OS: save(filename). Ye 'virtual/extended machine' wala view hai — jaise real hardware ke upar OS ek 'behtar, simpler' fake machine bana deta hai.

Definition 3 — Control Program ke roop mein

"OS ek control program hai jo user programs ke execution ko control karta hai, taaki errors aur improper use of computer resources na ho."

Yani OS ye bhi ensure karta hai ki koi ek program galti se ya jaan-bujh kar doosre program ka data corrupt na kare, ya system crash na kare.

Note: Exam mein agar 'Define Operating System' pucha jaye, to teeno points combine karke likhna best hota hai — Resource Manager + Extended Machine + Control Program.