The National Bureau of Standards1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics-Electricity-Heat-Mechanics-Optical Physics-Linac genics3. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government agencies; and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry-Polymers-Metallurgy-Inorganic Materials-Reactor THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute also monitors NBS engineering standards activities and provides liaison between NBS and national and international engineering standards bodies. The Institute consists of the following divisions and offices: Engineering Standards Services-Weights and Measures-Invention and Programs. THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center consists of the following offices and divisions: Information Processing Standards-Computer Information-Computer Services THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum accessibility to the scientific information of the world, and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data-Office of Technical Information and 1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234. 2 Part of the Center for Radiation Research. U.S. DEPARTMENT OF COMMERCE, Peter G. Peterson, Secretary Nat. Bur. Stand. (U.S.), Tech. Note 734, 25 pages (June 1972) For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.46:734). Price 35 cents. 2140 1484 QUALITY CONTROL MARK OMNITAB II Segmentation Structure Sally T. Peavy and Ruth N. Varner OMNITAB II is an interpretive system developed and maintained by the National Bureau of Standards to enable scientists to use a large computer easily, effectively and accurately for numerical, statistical and data analysis without prior computer experience. The system is as machine independent as possible, making implementation relatively easy. Since OMNITAB II has a large memory requirement, segmentation and overlay are virtually essential. Overlay procedures are dependent upon the operating system of the computer. Changes are necessary to the OMNITAB II program when the overlay procedure requires specific overlay CALL statements to external procedures in other overlay links. This Technical Note describes a method of segmentation and overlay for a particular operating system (CDC-6000 series). The method can readily be adapted to other operating systems with modifications to the control statements. Key words: ANSI FORTRAN, general-purpose computer program, OMNITAB II is an interpretive computing system which permits easy use of a computer without prior computing experience. The system was developed and is maintained by the National Bureau of Standards to enable scientists to use a computer easily, effectively and accurately for numerical, statistical and data analysis without the necessity of becoming professional programmers. OMNITAB was envisioned by Joseph Hilsenrath and developed by him and his co-workers. A complete description of the first version of OMNITAB was given in Hilsenrath et al. (1966). Hogben et al. (1970 and 1971) documents OMNITAB II version 5.0, the present version. The OMNITAB II system was designed with the systems programmer in mind, as well as the user. All the subprograms in the system are written in the American National Standards Institute (ANSI) FORTRAN. Every effort has been made to produce a virtually machine independent program which could be easily transported and implemented on any large computer. However, a minimum number of modifications are necessary in the implementation of the ONITAB II system, due to the variability of hardware and software features of computers. The modifications are limited to a small number of subprograms and are fully documented in Peavy, Varner and Bremer (1970). same memory, assuming each real (floating point) number and a machine instruction Occupy one storage unit. The OMNITAB system consists of one main program, one-hundred-seventy-two procedure subprograms and four specification subprograms. To make the program operable on a smaller computer configuration, the OMNITAB II system has been segmented into twenty-one segments or groups. Certain of these segments may overlay each other (i.e., share the storage units in central memory). This reduces the storage units required to approximately 49K, plus the storage units needed by the operating system library subprograms (i.e., SIN, LOG, I/O routines, etc., approximately 4K). The amount of storage needed may be further reduced by decreasing the size of the worksheet and scratch areas as described in Peavy, Varner and Bremer (1970). Segmentation and overlay may not be necessary for a computer with a large central memory if the OMNITAB II program is permitted to utilize the full memory. Much thought has been put into the segmentation structure of the OMNITAB II program in order to minimize the swapping of segments in and out of the of the computer's central memory. Subprograms which read, scan and interpret the OMNITAB instructions are in the main segment which is in residence at all times during execution of the the OMNITAB system. The error checking subroutines are also included in this segment as well as a few of the subprograms which execute the most often used instructions (GENERATE, INCREMENT, RESET, etc.) as determined from statistics gathered over a three month period. The other segments contain subprograms which execute related instructions, such as the statistical, input-output, matrix and array operations. In order to maintain a minimum number of subprograms in the main segment, it was sometimes necessary to duplicate a subroutine in another segment a different subprogram name. This was avoided as much as possible. under The overlay procedure is very dependent upon the operating system of the computer. Since standards have not been defined in regards to overlay, the method of overlaying is at the discretion of the systems programmers or the software manufacturers. Some systems make great demands on the user or programmer, while others require a minimum amount of effort. From the authors' experience and knowledge of overlay procedures, there appear to be three main categories for third generation computers. In all three types the user must provide the following information to the operating system (1) how the subprograms are to be grouped, (2) which subprograms comprise the main segment and are in memory at all times, (3) (3) which groups may overlay what other groups and (4) what other groups or segments are necessary with a particular group. Furthermore, some overlay procedures have restrictions of the use of the FORTRAN labeled and unlabeled COMMON statements, of which the user must be aware to take proper action. One type of overlay procedure places no restrictions on the programmer when a problem is being programmed. During the programming stage of the problem no thought of overlay and segmentation structure are necessary. The programmer programs the problem as though the whole program will be able to reside in the computer at execution time. The operating system does not require the subprograms to be arranged in the order in which they are grouped when overlaid at execution time. Nor is it necessary to to precede each subprogram with control cards for the operating system. The only prerequisite is that at execution time, the operating system must be provided with either a set of control routine outlining the segmentation and overlay structure. This is the overlay procedure that was used in implementing OMNITAB II version 5.0 for the NBS computer configuration. For complete details see Peavy, Varner and Bremer (1970). statements or a The second second form of overlay procedure also does not restrict the programmer when the problem is being programmed. However, before execution the program units must be arranged in order of the overlay setup. Furthermore system control cards must precede each of the grouped procedures or segments. If OMNITAB II version 5.0 is is being implemented on a computer whose operating system allows this procedure for overlaying, the systems programmer should check Peavy, Varner and Bremer (1970) for details in deck setup. The third form of overlay procedure requires the programmer to keep in mind that the program will have to be segmented and overlaid because of its size. He must plan the |