Sierra Chart & ACSIL Glossary
Plain-language definitions for the order flow, volume profile, execution, and ACSIL terms you actually encounter as a Sierra Chart trader. 56 terms across 7 categories.
Order flow
Concepts and signals derived from per-tick bid/ask volume, depth, and trade direction.
Order flow
The study of per-tick trade direction (buyer-initiated vs seller-initiated) and resting liquidity (bid/ask depth) to infer short-term price intent. Surfaces include delta, footprint, CVD, single prints, and market depth heatmaps.
Delta
The signed difference between buyer-initiated volume (trades at the ask) and seller-initiated volume (trades at the bid) over a given period — bar delta, session delta, or instantaneous delta.
CVD
Cumulative Volume Delta — the running sum of per-bar delta over a session or longer window. Reveals net buying or selling pressure independent of price.
Bid/ask volume
Per-tick trade volume split by side of the spread: volume traded at the ask is buyer-initiated, volume traded at the bid is seller-initiated. The raw input to delta, footprint, and CVD computations.
Footprint chart
A bar chart where each bar displays per-price-level bid and ask volume inside the bar — typically as side-by-side columns or as a numbers grid. Sierra Chart natively supports footprint via Numbers Bars.
Absorption
A pattern where price fails to move despite significant aggressive volume on one side — interpreted as passive size soaking up initiative orders. Often flagged as a counter-direction delta with limited price travel.
Single print
A price level traded with volume on only one side of the spread — bid-only or ask-only — leaving an untested footprint. The market frequently returns to single prints later in the session to fill them.
Zero print
Equivalent term to single print — a tick or level where bid (or ask) volume is zero, indicating one-sided liquidity that the market may revisit.
Market depth
The aggregated resting bid and ask order quantities at price levels around the inside market — the order book. Sierra Chart records depth in real time and offers a native Market Depth Historical study.
DOM
Depth of Market — the resting bid/ask order ladder around the inside spread. Sierra Chart includes a configurable DOM panel and exposes depth data to ACSIL.
Market depth heatmap
A color-coded visualization of historical resting depth quantities over time — typically rendered as a horizontal price-by-time grid where intensity encodes resting size. Sierra Chart provides this via the Market Depth Historical Graph.
Tape reading
Real-time observation of the time-and-sales feed — the chronological stream of executed trades with price, size, and time — used to infer aggression and intent.
Order book imbalance
A measurable skew between resting bid and ask quantities in the depth ladder — often expressed as a ratio (e.g., bid size / ask size at the top N levels). Persistent imbalance is interpreted by some traders as short-term directional pressure, though it can also reflect spoofing.
Iceberg order
A large order broken into small visible slices that re-post as each slice fills, hiding the true size from the public order book. Often inferred from the tape when a price level keeps absorbing aggressive volume without the displayed size shrinking.
Liquidity pool
A cluster of resting orders or stop-loss orders concentrated around a recognizable price level — prior highs/lows, round numbers, or session extremes — that acts as a magnet for price because filling them rewards larger participants.
Volume profile & TPO
Vertical-axis distribution of traded volume across price levels, plus TPO / market profile derivatives.
Volume profile
A horizontal histogram showing total traded volume at each price level across a session (or any custom window). Reveals where the market spent the most time accepting price.
VAP (Volume at Price)
Volume at Price — per-price-level traded volume data, the underlying tick-level input to volume profile and footprint visualizations. Sierra Chart exposes VAP arrays to ACSIL via `c_VAPContainer`.
POC
Point of Control — the price level with the highest traded volume inside a profile window. The visual peak of the volume profile, often acted on as a magnet or fade level.
VAH / VAL
Value Area High and Value Area Low — the upper and lower bounds of the price range containing the central 70% of volume in a profile. Used as session-scoped support / resistance.
Naked POC
A prior-session Point of Control that price has not revisited since it was formed. Commonly tracked as a magnet level for future sessions.
TPO
Time Price Opportunity — a market profile concept where each price level is annotated with letters representing the time brackets during which price traded there. Aggregates a session into a visual distribution.
HVN (High Volume Node)
High Volume Node — a price slot in a volume profile where significantly more contracts traded than at neighboring levels. HVNs mark zones the market has accepted as fair, and they often act as support, resistance, or magnets on subsequent revisits.
LVN (Low Volume Node)
Low Volume Node — a price slot in a volume profile where very little traded volume accumulated, typically a gap between two HVNs. LVNs represent zones the market rejected; price tends to travel through them quickly when revisited.
Execution
Order types, position sizing, and the mechanics of placing trades.
Position sizing
The mechanism that decides how many contracts to trade based on account size, risk per trade, and stop distance. Proper sizing is the single biggest determinant of long-term outcome.
Risk per trade
The maximum dollar (or percentage of account) amount at risk on a single trade — measured as the distance from entry to stop loss times contract size. Drives position sizing.
R-value
A trade's outcome expressed as a multiple of initial risk — a 2R win means the trade gained 2× its stop distance. Normalizes performance across instruments and position sizes.
Stop loss
A pre-committed exit price that closes a position at a defined loss if reached. The reference point for risk-per-trade and R-value calculations.
Trailing stop
A stop loss that automatically follows price in the trade's favor — typically by a fixed tick distance or a percentage of the bar range — locking in gains as the trade progresses.
OCO order
One-Cancels-Other — a paired order where the execution of one side automatically cancels the other. Used for stop / take-profit brackets and for trailing exit logic.
MFE
Maximum Favorable Excursion — the best unrealized profit a trade reached before being closed. High MFE on losers signals poor exits; low MFE on winners signals over-tight targets.
MAE
Maximum Adverse Excursion — the worst unrealized loss a trade reached before being closed. High MAE on winners signals stop placement that's too tight; low MAE on losers signals stops that work as intended.
Drawdown
Peak-to-trough decline in account equity, expressed in dollars, percentage of account, or R-multiples. Maximum drawdown over a backtest or live period is a primary input to position sizing and to evaluating whether a strategy is survivable.
Sharpe ratio
A risk-adjusted return metric: the mean excess return divided by the standard deviation of returns, typically annualized. Higher Sharpe means more return per unit of volatility — useful for comparing strategies with different risk profiles.
Profit factor
Gross profits divided by gross losses over a sample of trades. A single-number threshold-of-profitability metric: above 1 means the system makes money in aggregate, and most discretionary traders look for at least 1.5–2 to absorb costs and variance.
ACSIL & development
Sierra Chart's Advanced Custom Study Interface and Language — the C++ surface SCS studies are built on.
ACSIL
Sierra Chart's Advanced Custom Study Interface and Language — the native C++ interface used to write custom studies that compile to DLLs and run inside the platform.
scsf_ function
The C++ entry point convention for every Sierra Chart custom study. A study's main function is named `scsf_<StudyName>` and is the function the platform invokes on each chart pass.
sc.Subgraph
The output channel of a Sierra Chart study — a plotted series accessible as `sc.Subgraph[index][bar]`. Studies can expose up to 256 subgraphs for lines, points, bars, or text overlays.
sc.Input
A user-editable parameter exposed by a Sierra Chart study, configured via the study settings dialog. Inputs can be numbers, booleans, paths, time of day, colors, etc.
Auto-looping
The default ACSIL execution mode where Sierra Chart calls a study once per bar, walking from oldest to newest. Disable to handle the full chart in a single call (manual looping), useful for studies that compute aggregates across all bars.
SCDLLName
The macro that registers a study's display name and DLL identity inside Sierra Chart. The string passed to SCDLLName is what users see in Analysis → Studies → Add Custom Study.
Graph ID
Sierra Chart's internal numeric identifier for a study instance on a chart, used when one study needs to read another's output (subgraph data, input values, computed arrays). Typically retrieved via the Study Settings dialog or programmatically through ACSIL helper functions.
Persistent variables
ACSIL state slots that survive across study function calls — typed accessors such as `sc.GetPersistentInt`, `sc.GetPersistentFloat`, and `sc.GetPersistentString` let a study remember values from one bar (or one tick) to the next without using subgraphs or external files.
Sierra Chart platform
Concepts specific to the Sierra Chart trading platform itself — chartbooks, instances, data files.
Chartbook
Sierra Chart's native saved-workspace format — a `.cht` file containing the charts, studies, layouts, and settings for a configured trading screen. Re-opens identically the next session.
Numbers Bars
Sierra Chart's native footprint chart type — each bar displays per-price-level bid and ask volume as numbers or graphics inside the bar. The platform's foundation for in-bar order flow analysis.
SCID file
Sierra Chart's native binary tick storage format — `.scid` files contain per-tick price, volume, and bid/ask data, written by the data feed and consumed by both the platform and external tools (e.g., the SCS Trading Journal for intra-trade PnL curves).
Sierra Chart
A professional Windows-based trading platform with a deep ACSIL programmable interface, native footprint and depth tooling, and direct connectivity to most futures data vendors and brokers.
Futures markets
Contract specifications, sessions, and structural characteristics of liquid futures.
RTH
Regular Trading Hours — the cash-session window for an instrument. For US equity index futures, RTH typically runs 9:30am to 4:00pm Eastern.
ETH
Extended Trading Hours — the overnight session running outside the cash session for an instrument. Liquidity is typically thinner and ranges more compressed than RTH.
Micro contract
A reduced-size futures contract — typically one-tenth of the standard contract's notional value (e.g., MES vs ES, MNQ vs NQ). Allows finer position sizing at smaller account levels.
Tick size
The smallest legal price increment for an instrument — for example $0.25 on ES, $0.25 on NQ. Combined with tick value, determines the dollar P&L per tick of price movement.
Prop firm
A proprietary trading firm that provides capital to traders who pass an evaluation. In the futures retail space, examples include Apex, Topstep, MyFundedFutures, Tradeify, and TakeProfit.
See these concepts in action across the SCS catalog.
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