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+---
+bc-version: [all]
+domain: style
+keywords: [casing, intrinsic-function, built-in-function, message, error, confirm, strsubstno, legacy, c-al, pascalcase]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# Intrinsic AL function calls use modern casing, not legacy ALL-CAPS
+
+## Description
+
+AL is case-insensitive, so `MESSAGE(...)`, `ERROR(...)`, `CONFIRM(...)`, and
+`STRSUBSTNO(...)` compile and run identically to `Message(...)`, `Error(...)`,
+`Confirm(...)`, and `StrSubstNo(...)`. Modern AL — the VS Code tooling's
+default formatter output, Microsoft's own current samples, and the BCApps
+codebase — writes intrinsic/built-in function calls in the casing Microsoft
+assigns to the function's declared name (typically PascalCase). ALL-CAPS
+calls are a holdover from classic C/AL (C/SIDE) and signal code that has not
+been modernized, even though it compiles and runs correctly.
+
+This is a distinct concern from CodeCop AA0241
+([[lowercase-reserved-keywords]]), which governs reserved keywords (`if`,
+`begin`, `var`, `for`, ...) and explicitly excludes identifiers and function
+calls. Intrinsic function names are identifiers, not keywords, so AA0241
+does not catch ALL-CAPS intrinsic function calls — which is exactly why the
+pattern survives unflagged from old training material and legacy modules
+into new development.
+
+## Best Practice
+
+```al
+Message('%1 records updated.', Count);
+if not Confirm('Delete %1?', false, CustomerNo) then
+    exit;
+Error(StrSubstNo('%1 must not be blank.', FieldCaption("No.")));
+```
+
+## Anti Pattern
+
+```al
+MESSAGE('%1 records updated.', Count);
+IF NOT CONFIRM('Delete %1?', FALSE, CustomerNo) THEN
+    EXIT;
+ERROR(STRSUBSTNO('%1 must not be blank.', FieldCaption("No.")));
+```
+
+ALL-CAPS intrinsic function calls (`MESSAGE`, `ERROR`, `CONFIRM`,
+`STRSUBSTNO`, `CALCDATE`, `COPYSTR`, and similar) trip no current CodeCop
+diagnostic, but they are a reliable signal that a code block was copied from
+old C/AL material, a pre-2018 upgrade, or outdated training content rather
+than written or reviewed against current AL conventions.