CISC181 9am 02/14/05

(1) (Continue?) going over the Farenheit to Celsius program at:

   http://udel.edu/~pconrad/cisc181/05S/work/labs/lab01/lab01b.cc



Three ways to handle the std:: stuff

(1) separate statment (e.g.) for each item used,
    using std::cout;
    using std::cin;
    using std::endl;
    etc.

(2) using namespace std;

(3) put it before every reference in the program;

    std::cout << "Hello World " << std::endl;


    For reasons that are more apparent when you are working on 
    a large real-world project, in the real world (professional
    large scale c++ development, method 1 is preferred)

    On labs, projects, and anything you do for this class where
    time is not an issue, I would prefer you to use method 1 or 3 (or a combination of
    both).

    When time is an issue, e.g. in lecture, quizzes, or exams,
    method 2 (lazy way)  is perfectly acceptable.

 Types:

     int for integers
     float or double for real numbers

     double is almost always preferred over float
     you need to know that float exists, but you should almost always
        use double instead.

     The number of bits used to represent int, float, double can vary
     from system to system.
  
     On strauss how big is an int, float or double?   How can we tell?

     Use the built-in feature of C++ "sizeof".

   (side note on emacs: to visit another file,
     use CTRL/X, CTRL/F).

   (another emacs side note:  

      CTRL/A beginning of line
      CTRL/E end of line 
      CTRL/K kill line   ... actually, only kills from cursor to end of line
      CTRL/Y yank (paste)
      CTRL/spacebar OR CTRL/shift-2 "set mark"
      CTRL/W  "wipe" ... corresponds to "cut" (cuts whole "region")
      esc-W  (written M-w "meta-w") copy
          of "region" (between "point" and "mark"... "point" is where the cursor is.
      )
      
      CTRL/X CTRL/X  (type it twice): "exchange point and mark"

      type CTRL/X four times, and you'll see the extent of the region.

      CTRL/X  K  (not CTRL/X CTRL/K)  is "kill buffer"... doesn't delete the file,
              just says "don't visit this file anymore... "


If you are in a terminal session in emacs, and you want to drop to 
a command line temporarily, use "CTRL/Z" to temporarily drop to 
a command line (putting emacs in the "background".)  Use "fg" at the
command line to bring emacs back into the "foreground".

Read more about "foreground" and "background" in your Just Enough Unix textbook
by Anderson.. these are important Unix concepts.

CTRL/X B (not CTRL/X CTRL/B) allows you to switch between two files you
are "visiting" in emacs.

CTRL/X CTRL/W is how you do a "save as" (W stands for "write file").

CTRL/X  1   one window
CTRL/X  2   two windows horiz
CTRL/X  3   two windows vert
CTRL/X o  (letter oh) is "other window"
CTRL/X 0  is "zero out this window"


 Compiling the "sizeofDemo.cc" program

> make demoSizeof.cc
`demoSizeof.cc' is up to date.
> make demoSizeof
CC    -o demoSizeof demoSizeof.cc 
> make demoSizeof
`demoSizeof' is up to date.
> ./demoSizeof 
sizeof(a) is 4
sizeof(b) is 8
sizeof(c) is 4
sizeof(int) is 4
sizeof(float) is 4
sizeof(double) is 8

(3) Modifying the farenToCelsius program to do milesToKm conversion.

(4) Modifying that program to use a loop to print a table of values.





(5) Review Compling on strauss (we did this last time, but lets make sure we covered all of this)

   ">" means the Unix prompt
 
   Show how to compile this with just 
        > CC lab01b.cc
        > ./a.out

   Show same result with just g++ and then running a.out

        > g++ lab01b.cc
        > ./a.out

   Show that we can rename to lab01b.cpp and it doesn't matter.

         > mv lab01b.cc lab01b.cpp
         > g++ lab01b.cpp
         > ./a.out
 
   Show that we can name the executable something else with the -o switch:

   > g++ lab01b.cpp -o lab01b
   > ./lab01b

   You need the . if "." is not in your path
   > ./lab01b

   You don't need the . if "." is in your path
   > lab01b

   How do we know if . is in the path?

   > echo $PATH

   How do we change our path (under csh or tcsh) ?
   What is csh or tcsh?

      emacs ~/.cshrc
      emacs ~/.localenv

   Using the "which" command to know where the compiler is
   coming from.

(6) Convert first program from last time (written in fictional language) 
    into C++

BEFORE:

// y<x is a boolean expression, either true or false

integer total, max, count, input   // declare four variables
count = 0                // initializing two of them
total = 0                // assignment statements
read max               // getting user input for variable max
while (count < max)    // loop count from 0 to the number inputted
  begin
  read input
  total = total + input
  count = count + 1
  end
print total      // better name for w: total of all the z's
end


AFTER:

// y<x is a boolean expression, either true or false

integer total, max, count, input   // declare four variables
count = 0                // initializing two of them
total = 0                // assignment statements
read max               // getting user input for variable max
while (count < max)    // loop count from 0 to the number inputted
  begin
  read input
  total = total + input
  count = count + 1
  end
print total      // better name for w: total of all the z's
end


(7) Another program, demonstrating "while loop" and "if/else"

   http://udel.edu/~pconrad/cisc181/05S/lect/code/9am/02.11/min-max.cc

Note that there is no prompt for input.

Note that you can type all five numbers on the same line, or 
on 5 different lines, or mix and match.

Note that if you type in 6 numbers, 6th one is ignored.

What happens if you mix non-numerics in with the numerics?