Where the parameters are:

operation

Specifies the operation to perform. This parameter is the name of a field that contains character data of length 10. The allowable values are:

ABSTOREL

calculates the relative track number on the volume from the passed cchh1 track address.

COMPARE

compares the two track addresses passed in cchh1 and cchh2.

EXTRACTCYL

extracts the 28-bit cylinder number from the passed cchh1 track address.

EXTRACTTRK

extracts the 4-bit track number from the passed cchh1 track address.

NEXTTRACK

increments the track address by one track and increments the cylinder number if necessary from the passed cchh1 track address.

NORMALIZE

reverses the 16-bit and 12-bit portions of the cylinder number from the passed cchh1 track address. The CCCCcccH becomes cccCCCCH. This could be used to subsequently perform unsigned comparisons of track addresses.

NORMTOABS

reverses the 12-bit and 16-bit portions of the cylinder from the track address passed in number. The cccCCCCH becomes CCCCcccH. Use this to convert a normalized track address to an absolute 28-bit cylinder address.

RELTOABS

converts a relative track number, passed in number, to a 28-bit cylinder address.

SETCYL

converts a relative cylinder number, passed in number, to a 28-bit cylinder address and sets the head portion to zero.

If you request an operation that is less than 10 characters, it must be padded on the right with blanks.

cchh1

Required parameter, cchh1, is a four-byte area containing a track address that nominally is in the form of CCHH. For all functions except RELTOABS and SETCYL this is input to the called routine. For RELTOABS, SETCYL, and NORMTOABS this is output from the called routine.

cchh2

Optional positional parameter, cchh2, is a four-byte area whose meaning depends on the operation specified by the first parameter. For all functions except COMPARE and NEXTTRACK this parameter is ignored.

For COMPARE processing, cchh2 contains the track address that is to be compared to the first cchh1 parameter.

For NEXTTRACK processing, cchh2, is the four-byte output area to contain the track address (CCHH) of the next logical track on the volume. If the input track number is 0 to 13, the output cylinder number will be the same and the output track number will be one greater than the input track number. If the input track number is 14, the output cylinder will be one higher than the cylinder number in cchh1 and the output track number will be 0. The called routine does not check for numeric overflow.

number

Optional positional parameter, number, is a four-byte integer whose meaning depends on the operation specified by the first parameter.

For ABSTOREL processing, number is the output area that will contain the relative track number on the volume.

For COMPARE processing, number is the output area that will contain the result of the comparison. Zero means the inputs are equal. Negative one means the first one is lower. Positive one means the first one is higher.

For EXTRACTCYL processing, number is the output area that will contain the 28-bit cylinder number with the four high order bits set to zero.

For EXTRACTTRK processing, number is the output area that will contain the four-bit track number with the 28 high order bits set to zero.

For NEXTTRACK processing, number is an ignored parameter. It can be 0 or any valid virtual address. Not checked by the called routine.

For NORMALIZE processing, number is the output area that will contain the normalized version of the input CCHH. The CCCCcccH becomes cccCCCCH. The high order 28-bits are the cylinder number and the low order four bits are the track number. This allows your code to do a more efficient comparison of one track address with many track addresses. Normalize each and do unsigned comparisons.

For NORMTOABS processing, number is the input area that contains the normalized track address to be converted. The cccCCCCH becomes CCCCcccH. Use this to convert a normalized track address to an absolute 28-bit cylinder address.

For RELTOABS processing, number is the input area that contains the relative track number on the volume. For example the first two tracks on the second cylinder (cylinder 1) have relative track numbers of 15 and 16. The called routine converts the relative track number to a 28-bit nonlinear cylinder address with a 4-bit head value in the low order four bits in the cchh1 output area.

For SETCYL processing, number is the input area that contains the cylinder number on the volume in the low order 28-bits with the four high order bits set to zero. The called routine splits the 28-bits into the high order 12-bits and low order 16-bits, reverses them in the output field, cchh1, with the cylinder address in the high order 28-bits and the low order four bits to zero

returncode

returncode is a 4-byte integer that contains the return code from IECTRKAD processing. returncode is also returned in register 15. The return codes that could be set include the following:

0

Successful.

4

Successful, but with exceptions

8

Request was unsuccessful because of invalid or incorrect input. Refer to thereasoncode for more detailed information

reasoncode

reasoncode is a 4-byte integer associated with a specific return code. reasoncode is returned in Register 0.

No reason codes are supplied for return code 4:

The following reason codes are supplied for return code 8:

4

The H portion of a track address is not valid on a NEXTTRACK operation

8

The caller specified an invalid operation (the first parameter is not one of the supported operations)

12

The address of a required parameter is zero.