- Character set - Character escape conventions - Canonical form - - - PowerPoint PPT Presentation

character set
SMART_READER_LITE
LIVE PREVIEW

- Character set - Character escape conventions - Canonical form - - - PowerPoint PPT Presentation

CHARACTER STREAM PROCESSING - Character set - Character escape conventions - Canonical form - Line editing conventions CHARACTER SET CONSIDERATIONS minimum: graphic range equal to a typical office typewriter support: throughout system -programs


slide-1
SLIDE 1

CHARACTER STREAM PROCESSING

  • Character set
  • Character escape conventions
  • Canonical form
  • Line editing conventions
slide-2
SLIDE 2

CHARACTER SET CONSIDERATIONS

minimum:

graphic range equal to a typical office typewriter support: throughout system

  • programs and data files

program language literals symbolic file names symbolic subroutine linkage punched cards

typewriters and displays printers

slide-3
SLIDE 3

CHARACTER STREAM PROCESSING CONSIDERATIONS

1. Device Independence--any program with any terminal, 2.

Unambiguous relation between

printed image and stored string.

slide-4
SLIDE 4

EXAMPLE OF DEVICE INDEPENDENT, UNAMBIGUOUS CHARACTER SET SUPPORT

stored

flies

User Procr

am 1-1~

Supervisor Subroutine

Llnslde: ASCII

canonical form ASCII

non-e~nonlcal

edltln& characters

EBCDIC

non-canonical escapes for ASCII codes edltln& characters no unlnterpreted edltlnc or escape characters

slide-5
SLIDE 5

ESCAPE CONVENTIONS FOR DEVICE INDEPENDENCE Typed at 2741 terminal: y = board_position <i,j >;

Character string passed to program:

y = board_position l,j ;

slide-6
SLIDE 6

CANONICAL REDUCTION EXAMPLE 1.

(user) locate "order"

2. ( edItor)

the order has been f i I ed.

3.

(user)

change "1." to II .!1." 4. (edl tor) the order has been f i J

] !i:d •

slide-7
SLIDE 7

CANONICAL REDUCTION METHOD

typed:

f.Qr.

that stored:

1. Graphics typed in the same column

are In ASCU collating sequence, separated by backspaces.

2. White space is represented by ASCII "blank" characters regardless

  • f how typed.
slide-8
SLIDE 8

Ll NE AND PRINT POSITION ED I Tl NG

1. typed: y = lenz#gth(string4);

stored:

y • length(strlng4); 2.

typed: Silncer@Sincerly## yours,

stored: Sincerely yours,

3.

typed:

we have ~#U#.liQ

1

eft.

stored:

we have .lllQ left.

slide-9
SLIDE 9

OBSERVATIONS FROM USAGE

  • Economically implementable
  • Effective human interface
  • User can Ignore special features

until needed

  • Interaction between canonical form

and horizontal tabulation