IBeam (⌶
) is a primitive ambivalent function or monadic operator that takes a numeric code as an argument/operand and provides a range of adhoc operations. This range covers nonprimitive functions, for example experimental features, interpreterlevel control, access to the environment, and information about APL itself.
History
IBeam was introduced in APL\360 as an ambivalent function for implementers to execute IBM System/360 (IBeam being pronounced very similarly to IBM) instructions from program control. The convenience of this lead to IBeam becoming directly available for use by anyone.^{[1]} However, modern IBMderived APLs replace all IBeams with quad names. For example, 5⌶
became ⎕DL
(Delay) while changing time unit from jiffies of 1⁄300^{th} of a second to a whole second.
Later, after it became common to use arrays as operands, Dyalog APL 12.1 began using the glyph as an operator where the operand selects functionality. It is used for testing experimental features, some of which may eventually become primitives or quad names. For example, 819⌶
became ⎕C
(Case Convert), while introducing distinction between case folding (for case insensitive comparisons) and case mapping (for human presentation forms).
Mnemonics
In general, IBeam's numeric operand isn't intended to be easily recalled. But some are given meaningful names.
One method is to devise a name from the Roman numeral letters I, V, X, L, C, D, and M:^{[2]}
IBeam 
Numeral

Colour Coding 
CC (200)

Colour Coding Information 
CCI (201)

Called Monadically 
CM (900)

Line Count 
LC (50100)

External links
References
APL builtins [edit]

Primitives (Timeline) 
Functions

Scalar

Monadic

Conjugate ∙ Negate ∙ Signum ∙ Reciprocal ∙ Magnitude ∙ Exponential ∙ Natural Logarithm ∙ Floor ∙ Ceiling ∙ Factorial ∙ Not ∙ Pi Times ∙ Roll ∙ Type ∙ Imaginary ∙ Square Root ∙ Round

Dyadic

Add ∙ Subtract ∙ Times ∙ Divide ∙ Residue ∙ Power ∙ Logarithm ∙ Minimum ∙ Maximum ∙ Binomial ∙ Comparison functions ∙ Boolean functions (And, Or, Nand, Nor) ∙ GCD ∙ LCM ∙ Circular ∙ Complex ∙ Root

NonScalar

Structural

Shape ∙ Reshape ∙ Tally ∙ Depth ∙ Ravel ∙ Enlist ∙ Table ∙ Catenate ∙ Reverse ∙ Rotate ∙ Transpose ∙ Raze ∙ Mix ∙ Split ∙ Enclose ∙ Nest ∙ Cut (K) ∙ Pair ∙ Link ∙ Partitioned Enclose ∙ Partition

Selection

First ∙ Pick ∙ Take ∙ Drop ∙ Unique ∙ Identity ∙ Stop ∙ Select ∙ Replicate ∙ Expand ∙ Set functions (Intersection ∙ Union ∙ Without) ∙ Bracket indexing ∙ Index ∙ Cartesian Product ∙ Sort

Selector

Index generator ∙ Grade ∙ Index Of ∙ Interval Index ∙ Indices ∙ Deal ∙ Prefix and suffix vectors

Computational

Match ∙ Not Match ∙ Membership ∙ Find ∙ Nub Sieve ∙ Encode ∙ Decode ∙ Matrix Inverse ∙ Matrix Divide ∙ Format ∙ Execute ∙ Materialise ∙ Range

Operators 
Monadic

Each ∙ Commute ∙ Constant ∙ Replicate ∙ Expand ∙ Reduce ∙ Windowed Reduce ∙ Scan ∙ Outer Product ∙ Key ∙ IBeam ∙ Spawn ∙ Function axis ∙ Identity (Null, Ident)

Dyadic

Bind ∙ Compositions (Compose, Reverse Compose, Beside, Withe, Atop, Over) ∙ Inner Product ∙ Determinant ∙ Power ∙ At ∙ Under ∙ Rank ∙ Depth ∙ Variant ∙ Stencil ∙ Cut ∙ Direct definition (operator) ∙ Identity (Lev, Dex)

Quad names

Index origin ∙ Comparison tolerance ∙ Migration level ∙ Atomic vector
