Page:FORTRAN IV enhanced character graphics (IA fortranivenhance5003wolc).pdf/5

 FORTRAN IV ENHANCED CHARACTER GRAPHICS

N. M. Wolcott

National Bureau of Standards, Washington, D.C., 20234

ABSTRACT. A FORTRAN IV subroutine is described which allows the drawing of six styles of alphabetic characters, three styles of numbers, and 48 special mathematical symbols from the enhanced graphic character set of Dr. A. V. Hershey. Twenty two symbols for graph plotting are also provided. Output is by linkage to an external subroutine PLOT. The program requires a computer which can accommodate a 30 bit word-length.

Key words: Alphabets; CCM; computer graphics; computerized typesetting; digital plotting; plotting; type fonts; type setting; vectorized characters

I. INTRODUCTION. The enhanced graphic characters of Dr. A. V. Hershey (1), (2) are suitable for use on pen plotters or computer output microform devices using vector graphics. The subroutines presented here are an extension of those previously developed (3) to make the Hershey characters available with subroutines conforming as closely as possible the American Standards Association FORTRAN IV Standard (4) so as to to be useable on a variety of computers. The characters provided include the SIMPLEX ROMAN, SIMPLEX GREEK, DUPLEX ROMAN, COMPLEX ROMAN, COMPLEX GREEK, and COMPLEX ITALIC alphabets; SIMPLEX, COMPLEX,and DUPLEX numerals (as described in Refs (1) and (2)); and 48 special characters and mathematical symbols.

II. COMPUTER ORGANIZATION. The data to describe the characters and symbols are included in a BLOCK DATA subprogram of about a thousand cards. The data are in the form of decimal integers less than 2**30 to accommodate a variety of computer word-lengths. The current 30 bit implementation allows the encoding of two (x,y) pen instructions per computer word. Each 15 bit pen instruction contains 3 bits of pen up or pen down information, 6 bits of x-coordinate information, and 6 bits of y-coordinate information. A zero instruction indicates the end of the character. In order to allow for textual input from various computers the input characters are limited to the 47 FORTRAN characters, that is A-Z, blank, 0-9, and + - / = *,. $.

Eleven additional non-FORTRAN characters are used for control information; these characters may be varied by local option at each computer site.

Partial word accesses are provided for by means of an internal FORTRAN FUNCTION:

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