Learn pre-market session behavior — Hinglish notes

4.4.2 · Stock-Market › When to Trade — Timing & Sessions

WHAT is the pre-market session?

HOW is the opening price found? (Call Auction — derived from scratch)

Pre-open mein call auction use hoti hai, continuous matching nahi. WHY? Kyunki kam players hone par hum pehle SAARE orders gather karna chahte hain, phir WOH EK price dhundhna chahte hain jo sabse zyada shares trade kare.

WHY yeh rule hai — step by step derivation:

Price $P$ par kya trade ho sakta hai? Buyer tabhi trade karega jab woh $\geq P$ dene ko taiyaar ho; seller tabhi jab woh $\leq P$ accept kare. Toh buyers-at-or-above = $D (P)$ , sellers-at-or-below = $S (P)$ .
- Why? Trade ke liye ek willing buyer AUR seller dono chahiye usi price par.
Kitne actually match honge? Tum chhoti side se zyada trade nahi kar sakte. Toh matched volume $= min (D (P), S (P))$ .
- Why the min? Agar 500 shares demand mein hain par sirf 300 offer hain, toh sirf 300 haath badlenge.
Woh $P^{*}$ chuno jo yeh sabse bada kare. Exchange maximum liquidity aur fairness chahta hai.
- Why max? Executed volume maximise karna woh price deta hai jahan supply aur demand sabse achhe "milte" hain.
Tie-breakers (agar do prices par equal volume ho): woh price chuno jis par minimum order imbalance $∣ D (P) - S (P) ∣$ ho; agar phir bhi tie ho, toh woh price jo previous close ke sabse kareeb ho.

Figure — Learn pre-market session behavior

Worked example Worked example — computing the opening price

Pre-open mein collect hue buy aur sell orders:

Price ₹	Buy qty (at ≥P) $D$	Sell qty (at ≤P) $S$	Match $= min$
100	700	200	200
101	500	400	400
102	300	600	300
103	100	800	100

Step 1: Har row mein $min (D, S)$ compute karo. Why? Sirf chhoti side hi trade kar sakti hai.
Step 2: Max match = 400 at ₹101. Why 101? Kyunki yeh tradable quantity maximise karta hai.
Result: Opening price $P^{*} = ₹101$ , open par 400 shares execute hote hain.

Key behavioral traits of the pre-market

Common mistakes (Steel-manned)

Active recall

Recall Quick self-test (answer before revealing)

NSE pre-open ki window kya hai? → 9:00–9:15 AM, matching 9:08–9:12 par.
Opening price ka rule kya hai? → Woh price jo matched (min) quantity maximise kare.
Do tie-breakers kya hain? → Min imbalance, phir previous close ke sabse kareeb.
Pre-market mein spreads wide kyun hote hain? → Low liquidity / thin order book.

Recall Feynman: explain to a 12-year-old

Shop officially khulne se pehle, kuch early customers aapas mein whisper karte hain ki woh kitna pay karenge aur sellers kitna maangenge. Shopkeeper sab likh leta hai, phir WOH EK price chunata hai jis par sabse zyada items kharide aur beche ja sakein. Kyunki wahan sirf mutthi bhar log hote hain, agar ek amir bachha bahut kuch khareedna chahe, toh price jaldi oopar jump kar sakti hai — isliye early prices jumpy hoti hain aur "asking" aur "offering" prices mein bada gap hota hai.

Flashcards

Pre-market (pre-open) session kya hoti hai?

Regular open se pehle ki ek trading window jisme low liquidity hoti hai aur opening price call auction ke through discover hoti hai. (NSE: 9:00–9:15 AM)

NSE pre-open ke teen phases kya hain?

Order entry 9:00–9:08, order matching 9:08–9:12, buffer 9:12–9:15.

Opening/equilibrium price kis rule se set hoti hai?

Woh price jo matched (tradable) quantity maximise kare, yaani min(Demand, Supply) maximise kare.

Matched quantity min(D,S) kyun hoti hai?

Trade ke liye buyer aur seller dono chahiye; chhoti side se zyada trade nahi ho sakta.

Agar do prices par equal volume ho toh pehla tie-breaker kya hai?

Minimum order imbalance |D−S|.

Imbalance ke baad doosra tie-breaker kya hai?

Previous close ke sabse kareeb wali price.

Pre-market mein bid-ask spreads wide kyun hote hain?

Thin order book / low participation matlab match karne ke liye kam resting orders.

Pre-market mein per-share volatility zyada kyun hoti hai?

Low liquidity matlab chhote orders se price bahut zyada move karti hai.

"Gap up/down" kya hota hai?

Jab opening price overnight news aur auction repricing ki wajah se previous close se sharply alag ho.

Pre-open mein use karne ke liye best order type kya hai?

Limit orders — thin books mein market orders buri prices par fill ho sakte hain.

Pre-market exist hi kyun karta hai?

Orderly opening price discover karne ke liye aur overnight information price in karne ke liye, taaki chaotic open se bacha ja sake.

Connections

Market Sessions Overview — trading day mein pre-open kahan fit hota hai
Call Auction Mechanism — yahan use hone wala matching engine
Gap Trading Strategies — open jump ko trade karna
Bid-Ask Spread & Liquidity — thin markets wildly behave kyun karte hain
Order Types — Market vs Limit — low liquidity mein safe execution
Overnight Risk & News Events — pre-market moves ka source