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     30 .\"	@(#)appen.C	8.1 (Berkeley) 6/8/93
     31 .\"
     32 .ie t .oh '\*(Ln Appendix A''PS1:19-%'
     33 .eh 'PS1:19-%''\*(Ln Appendix A'
     34 .el .he ''\fIAppendix A\fR''
     35 .bp
     36 .(x
     37 .ti 0
     38 .b "Appendix A"
     39 .)x
     40 .sh 1 "Examples" 1
     41 .pp
     42 Here we present a few examples
     43 of how to use the package.
     44 They attempt to be representative,
     45 though not comprehensive.
     46 Further examples can be found in the games section
     47 of the source tree and in various utilities that use the screen such as
     48 .i systat(1) .
     49 .sh 2 "Screen Updating"
     50 .pp
     51 The following examples are intended to demonstrate
     52 the basic structure of a program
     53 using the screen updating sections of the package.
     54 Several of the programs require calculational sections
     55 which are irrelevant of to the example,
     56 and are therefore usually not included.
     57 It is hoped that the data structure definitions
     58 give enough of an idea to allow understanding
     59 of what the relevant portions do.
     60 .sh 3 "Simple Character Output"
     61 .pp
     62 This program demonstrates how to set up a window and output characters to it.
     63 Also, it demonstrates how one might control the output to the window.
     64 If you run this program, you will get a demonstration of the character output
     65 characteristics discussed in the above Character Output section.
     66 .(l I
     67 .so t2.gr
     68 .)l
     69 .sh 3 "A Small Screen Manipulator"
     70 .pp
     71 The next example follows the lines of the previous one but extends then to
     72 demonstrate the various othe uses of the package.
     73 Make sure you understand how this program works as it encompasses most of
     74 anything you will need to do with the package.
     75 .(l I
     76 .so t3.gr
     77 .)l
     78 .sh 3 "Twinkle"
     79 .pp
     80 This is a moderately simple program which prints
     81 patterns on the screen.
     82 It switches between patterns of asterisks,
     83 putting them on one by one in random order,
     84 and then taking them off in the same fashion.
     85 It is more efficient to write this
     86 using only the motion optimization,
     87 as is demonstrated below.
     88 .(l I
     89 .so twinkle1.gr
     90 .)l
     91 .sh 3 "Life"
     92 .pp
     93 This program fragment models the famous computer pattern game of life
     94 (Scientific American, May, 1974).
     95 The calculational routines create a linked list of structures
     96 defining where each piece is.
     97 Nothing here claims to be optimal,
     98 merely demonstrative.
     99 This code, however,
    100 is a very good place to use the screen updating routines,
    101 as it allows them to worry about what the last position looked like,
    102 so you don't have to.
    103 It also demonstrates some of the input routines.
    104 .(l I
    105 .so life.gr
    106 .)l
    107 .sh 2 "Motion optimization"
    108 .pp
    109 The following example shows how motion optimization
    110 is written on its own.
    111 Programs which flit from one place to another without
    112 regard for what is already there
    113 usually do not need the overhead of both space and time
    114 associated with screen updating.
    115 They should instead use motion optimization.
    116 .sh 3 "Twinkle"
    117 .pp
    118 The
    119 .b twinkle
    120 program
    121 is a good candidate for simple motion optimization.
    122 Here is how it could be written
    123 (only the routines that have been changed are shown):
    124 .(l
    125 .so twinkle2.gr
    126 .)l
    127