Turbo Prolog

goal
1* Program 30 *1
makewindow(l,7,7,"Directory for disk AII,o,o,20,3S),
system("dir a:"),
makewindow(2,7,7,"Directory for disk B",o,L;o,2o,3S),
system("dir b:"),
makewindow(3,7,7,"I,21,2S,3,30).
Program 31 illustrates a file copy utility with a very elegant, window-driven user interface.
In this design, the user needn't remember whether it is the name of the copy or
the name of the file to be copied that comes first in the DOS copy command (a point of
confusion for many novice computer users). Program 31 uses the standard predicate
concat (see Chapter 9) which takes the form
concat(X,y,Z)
and is true if Z is bound to the concatenated strings to which X and Yare bound. Thus
concat("hello"," mother",X)
will succeed and binds X to "hello mother" and
concat("valerie","ann","valerie-ann")
fails (because of the extra hyphen in "valerie-ann").
goal
Date and Time
1* Program 31 *1
makewindow(l,7,7,ISource",o,o,2o,3S),
write("Which file do you want to copy ?"),
cursor(3,B),readln(X),
makewindow(2,7,7,IDestination",o,L;o,2o,3S),
write("What is the name of the new copy ?"),
cursor(3,B),readln(Y),
concat(X," ",Xl) ,concat(Xl, Y, Z),
concat("copy ",Z,W),
makewindow(3,7,7,IProcess",M,lS,B,So),
write(" Copying ",X," to ",Y),cursor(2,3),
system(W) .
There are two other DOS-related standard predicates that are handy to use: date and
time. They can each be used in two ways, depending on whether all their parameters
are free or bound on entry. If all variables in
time(Hours,Minutes,Seconds,Hundredths)
are bound, time will reset the internal system time clock. If all variables are free, they
will be bound to the current values of the internal clock.
Date, which also relies on the internal system clock, operates in the same way, and
takes the form
date(Year,Month,Day)
Program 32 uses time to display the time elapsed during a listing of the directory in
drive A.
88 Turbo Prolog Owner's Handbook