Compute Array Index (CAI)

Op Code (Hex)	Operand 1	Operand 2	Operand 3	Operand 4
1044	Array index	Subscript A	Subscript B	Dimension

Operand 1: Binary(2) variable scalar.

Operand 2: Binary(2) scalar.

Operand 3: Binary(2) scalar.

Operand 4: Binary(2) constant scalar object or immediate operand.

Description: This instruction provides the ability to reduce multidimensional array subscript values into a single index value which can then be used in referencing the single-dimensional arrays of the system. This index value is computed by performing the following arithmetic operation on the indicated operands.

Array Index =

Subscript A + ((Subscript B-1) X Dimension)

The numeric value of the subscript B operand is decreased by 1 and multiplied by the numeric value of the dimension operand. The result of this multiplication is added to the subscript A operand and the sum is placed in the array index operand.

All the operands must be binary with any implicit conversions occurring according to the rules of arithmetic operations documented in Arithmetic Operations. The usual rules of algebra are observed concerning the subtraction, addition, and multiplication of operands.

This instruction provides for mapping multidimensional arrays to single-dimensional arrays. The elements of an array with the dimensions (d1, d2, d3, ..., dn) can be defined as a single-dimensional array with d1*d2*d3*...*dn elements. To reference a specific element of the multidimensional array with subscripts (s1,s2,s3,...sn), it is necessary to convert the multiple subscripts to a single subscript for use in the single-dimensional array. This single subscript can be computed using the following:

s1+((s2-1)*d1)+(s3-1)*d1*d2)+...+((sn-1)*d*d2*d3*...*dm)

where m = n-1

The CAI instruction is used to form a single index value from two subscript values. To reduce N subscript values into a single index value, N-1 uses of this instruction are necessary.

Assume that S1, S2, and S3 are three subscript values and that D1 is the size of one dimension, D2 is the size of the second dimension, and that D1D2 is the product of D1 and D2. The following two uses of this instruction reduce the three subscripts to a single subscript.

CAI INDEX, S1, S2, D1      Calculates s1+(s2-1)*d1
CAI INDEX, INDEX, S3, D1D2 Calculates s1+(s2-1)*d1+(s3-1)*d2*d1

Authorization Required

None

Lock Enforcement

None

Exceptions

06 Addressing

0601 Space Addressing Violation
0602 Boundary Alignment
0603 Range

08 Argument/Parameter

0801 Parameter Reference Violation

0C Computation

0C0A Size

10 Damage Encountered

1004 System Object Damage State
1044 Partial System Object Damage

1C Machine-Dependent

1C03 Machine Storage Limit Exceeded

20 Machine Support

2002 Machine Check
2003 Function Check

22 Object Access

2201 Object Not Found
2202 Object Destroyed
2203 Object Suspended
2208 Object Compressed
220B Object Not Available

24 Pointer Specification

2401 Pointer Does Not Exist
2402 Pointer Type Invalid

2E Resource Control Limit

2E01 User Profile Storage Limit Exceeded

36 Space Management

3601 Space Extension/Truncation

44 Protection Violation

4401 Object Domain or Hardware Storage Protection Violation
4402 Literal Values Cannot Be Changed