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⟶ ACL ⟶ Literature ⟶ Progress Reports ⟶ SPROGS Notes

⟶ ACL ⟶ Literature ⟶ Progress Reports ⟶ SPROGS Notes

ACL ACD C&A INF CCD CISD Archives

Applications Associates Literature Society Technology Software revisited

Early history □ Minutes of committee meetings □ Progress reports □ Other reports □ News cuttings □ In-house publications □ Committee papers □ Personal recollections □ ACL publications □ Books □ Early Atlas publications □ FR80 reports □ Atlas manuals □ ICL1906A manuals □ Other manuals and papers

General □ Applications Software Group □ Basic Software Group □ FR80 □ FR80 operations □ FR80 project notes □ FR80 technical notes □ FR80 user notes □ Graphics □ Graphics Section □ Graphics Notes □ Graphics User Notes □ PDP15 □ PDP15 Notes □ SPROGS □ SPROGS Technical Notes □ SPROGS Papers □ SPROGS Notes

SPROGS Note No 11: Some useful display routines

W D Shaw, J R Gallop

27 October 1972

1. End of file condition

To remove the necessity of placing a marker word at the end of null files it is suggested that a length of file function, LNFL, be created. Thus:

(a) 
      LOAD ('P1', ANAME( 'FILENAME')) 
      LOAD ('P2',1.0) 
      LOAD ('P3',1.0) 
      LNFL ('LEN','P1','P2') 
      
      WHILE('P3','LE','LEN') 
           BEGINS 
           LOAD ('X',AR('P1','P2','P3')) 
           ADD('P3','1.0) 
           LOAD ('Y',AR('P1','P2','P3')) 
           ADD ('P3',1.0) 
           SETXY('X''Y') 
           ADUFLM
           ENDS

2. Execute command

The above example could be simplified by the addition of an execute command, XCT. The loop becomes:

(b) 
      LOAD('NOARGS',2.0) 
      NULLSET(DSRTNM('SETXY')) 
      WHILE('P3',LE,LEN) 
           BEGINS 
           XCT(P1,P2,P3) 
           ADD ('P3',PR2(NOARGS)) 
           ADUFLM 
           ENDS

XCT takes an array of index variable as its argument. It causes the NULLSET instruction to be executed with the arguments pointed to by the array. Thus, it is really a primitive form of DRAW on a NULL file. Another command XCTA (execute and add) would XCT then increment the third member of the array by the number of arguments in the command specified by NULLSET. Thus (b) becomes

(c) 
      NULLSET (DSRTN:' SETXY')) 
      WHILE('PS',LE,LEN) 
      BEGINS 
      XCTA('P1','P2','P3') 
      ADUFLM 
      ENDS

Thus, XCTA causes a 'SETXY' on each pair of arguments in the NULL file and increments P3 by 2.

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