The text read off it
[03.03.02]
The program elements of the chart are described as follows:
File Block — this is a 12-word File Control Block for each file required by the program.
File Lists — these are generated for each buffer pool, showing the group structure and the files assigned to the pool.
Define and Attach Calling Sequences — each buffer pool must be defined by a reference to the IOCS subroutine, DEFINE. Files are attached to this pool by reference to the ATTACH subroutine. These calling sequences are generated by the Loader and are the first instructions executed.
Transfer to Program Start — the instruction following the last ATTACH calling sequence is a transfer to the start point of the program.
Secondary and Primary Subroutines — three types of subroutines are used, Secondary, Primary, and Fixed.
Secondary subroutines — such subroutines, if called by the object program, are treated as program sections and are loaded following the end of the program in core storage.
Primary subroutines — certain object time subroutines are expected to have a large number of references in the object program. To avoid placing all instructions containing such references in the 2TEXT# file, primary subroutines, which are required to have a fixed length not modified by the loading process, are assigned core storage locations at the upper end of memory. This assignment is made at the time the first reference to the subroutine is encountered.
Fixed subroutines — all program references to points in IOEX, CTM and IOBS are defined by fixed subroutines, each of which has an assigned origin. These fixed