I have been active in the computer field since 1967. I am fortunate to have worked with a variety of systems from various vendors:
- IBM 7094, IBSYS.
- IBM System/360 OS.
- IBM 1620.
- IBM 1130.
- IBM System/360 DOS.
- DEC PDP-10, TOPS-10.
- Burroughs 5500, MCP.
- XDS Sigma 7, BTM, UTS.
- IBM System/360, /370, etc. VM.
- IBM System/z, VM/XA and /ESA, z/VM, MVS/XA and /ESA, z/OS.
- Intel x86 DOS, OS/2, Linux.
- various others, including DEC PDP-8, PDP-11, 1401, Univac 1108, IBM System/7.
- The PL/I programming language. I have been a PL/I enthusiast since 1967. I am an evangelist for the language, and also work to retrieve old PL/I software and documentation to make it accessible on the web. I manage"The PL/I Language", a website devoted to PL/I. I have a large collection of PL/I books and materials, and hope eventually to write a history of the language.
- OS/2. I started using OS/2 2.0 at introduction. I have been an OS/2 supporter and member of Team-OS/2. I have recently started using eCS.
- I am an editor for the Open Directory Project in the previous two categories.
- Since retirement in 2010 I have written a PL/I compiler, and founded and run Iron Spring Software. I hope to promote use of PL/I and maybe eventually make some money.
- Software Archeology. I would like to revive the Multics OS in some fashion, either via an emulator or, preferably, a port to x86 architecture.
- I have been a contributor to Wikipedia since 2008, mostly minor changes to articles in my areas of interest, and occasional articles on subjects where I have some knowledge and Wikipedia has no information.
- History, Archeology
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CDC 1604 Magnetic tape BCD codes
Access methods in OS/360
An area of storage called the Data Control Block (DCB) is the principal defined interface between the user's program and the access method. The DCB contains such information as the name of the DD statement referring to the dataset, the types of access allowed (read, write, update), and the size of the physical block on external storage. The DCB is built by a
DCB macro instruction in assembler, or by the compiler for a high-level language (HLL). For example the PL/I statement
DECLARE file1 INPUT RECORD FILE; will result in a DCB being constructed.
To initialize access to the dataset the program issues an
OPEN macro instruction or the equivalent HLL instruction.