D. CDC 3800 System Subroutines and Functions 



The subroutines used to open the file, position, read, and 

 write on the CDC 813 permanent disk are on-line COMPASS language 

 routines provided by the Naval Research Laboratory, Research 

 Computation Center Staff (Aiken, et al . , 1970). These subroutines 

 are DKOPEN, DKLOCATE , DKREAD, and DKWRITE. The subroutine DATA 

 is an off-line COMPASS language routine that retrieves the integer 

 day, month, and year from the computer's internal clock (Houston, 

 1969) . The function TIMELEFT is an on-line COMPASS language 

 routine that retrieves time marks from the computer's internal 

 clock. It is used to time various phases of the structuring and 

 accessing programs operation (Shannon, 1968). 



The on-line plotting subroutines PLOTS, PLOT, LINE, SYMBOL, 

 and AXIS are FORTRAN language routines. With the possible 

 exception of LINE and AXIS these routines are part of the standard 

 Calcomp plotter package (Gossett, et al., pending). 



Most of the previously mentioned subroutines and functions 

 are unique to the NRL CDC 3800 computer system. However, these 

 routines have counterparts on any large computer system, and 

 their replacement should pose little or no problem. 



PROFILE OUTPUT 



Two adjoining MSQLOC areas, 1291 and 1292, in the western 

 North Pacific Ocean were selected to test the computer program 

 and were digitized, structured, and placed on the random-access 

 storage device. The location of five test profiles along rhumb 

 lines, subsequently shown in figures 21, 22, and 23, are indexed 

 in figure 20. The contour chart used as an index chart shows 

 only part of the contour data that will input to the data base; 

 therefore, the test profiles show a slight difference in detail. 

 Figure 21, a profile through both MSQLOC areas, shows that the 

 link point between two data blocks is undetectable. This 530-nm 

 profile was generated in 7 seconds. 



In figure 22, composed of three profiles A, B, and C, a 

 dashed line is superimposed on each profile. The dashed lines 

 are profiles hand drawn by a bathymetrist , and the solid lines 

 are the computer profiles. All the profiles used the same data 

 base. Although the general shapes for both types of profiles are 

 the same, the cubic spline profiles show details between the 

 contour levels that would otherwise be lost if not captured by the 

 surface of gridded bathymetric data. This is especially true in 

 the more steeply sloping areas because the cubic spline considers 

 data adjoining the profile path. The three profiles in figure 22 

 show the system's ability to start a profile inside a MSQLOC area. 

 Figures 22A and 22C show profiles that terminate in gently sloping 



