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Display stream package September 3. 1975 1
Display stream package
A library package is now available which provides a capability
for display streams with considerably more flexihility than the current
operating system streams. Additional features include multiple fonts.
repositioning to any bit position in the current line (or, under proper
circumstances, any line). selective erasing and polarity inversion, and
better util ization of the availab'le bitmap space.
The package consists of two files, DSTREAM and DHANX. In
addition. the file DISP.D provides useful parameter and structure
declarations. in particular the parameters lOCB and 105 mentioned
below. DSTREAM is written in Bcpl and occupies about 2.4K (octal).
DHANX is written in assembly language and occupies about .1K (octal).
The package does not require any routines other than those in the
operating system.
1. Creating a display stream
CreateDstream(v, nl, ds, options)
creates a display stream. V is the samB 4-word vector currently used
for creating display streams through the operating system (see section
3.2.3 of the 0.5. manual). but, unlike tile 0.5., CreateDstream requires
that v be supplied and that v!O and v!l delimit a storage area. Nl is
the number of 1 ines for the stream: it is completely independent of the
amount of sflace supplied for bitmap and DCBs. Ds is a pointer to a
h I 0 c k 0 r I [) S V/O r d s wh i c h will be use d to s tor e the s t ream. its elf. If
ds is omitted. Cl'eateDstream will try to obtain such a block from the
0.5. using CHLAfES(v, DISPLAYOPErJ): tiltS procedure is not reCOrili11ended
in lJi~~\'! of. '. IH:\ ')mall nt.lIllber of .displ(lY str'ea''1S provided by the O.S.
Ine vaiue returned by CreateUstream is tile stream (dS if ds was
supplied).
The mlnlmum space for a display stream is lDCB