int light = green;
int red = 2;
while(light == green){
cout<<"I can drive through";
light = red;
}
This code is kind of silly, but it shows the point.
Now we can add out while() loop and condition.
#include < stdio.h >
|
Now, we going to make our program start doing things. We're going to add some code to our function that will tell us which month a person entered.
#include < stdio.h >
|
For a while, we're just going to look at the function. The rest of our program will remain the same until we are done with the get_date function.
//get_date function(so far).
|
switch() statement.
The switch statement is powerfull tool for making choices in
a program. The parameter is passed into the switch() statement
through the parentheses. The value passed should match one of the
case: values. In our situation, it's the months of
the year that are the values. break; allows us to
exit the switch() statement once our match has been found.
Between each case: and break; our assignment takes place.
This is the value that is passed out of the switch() and back to
our function.As you can see, the switch() starts with March. This is so because January and February are special and will be dealt with in different way.
//get_date function(so far).
|
if/else statement
that keeps us out of the switch() if the user enters January(1) or
February(2). If the user enters January, we add the day to the month
value and skip everything else. If the user enters February, we bypass
the section about Januray and then skip everything else. If the user
enters a different month, we bypass the January & February sections
and go right to the switch(). We have structured this this way
because of the next section we're going to add which will
determine if the year is leapyear. If the year is a leapyear, we
need an extra day added to the months after February. If
the date entered is February 29, the extra day is added already.
//get_date function(so far).
|
if/else statements.
if
The
if statement is a great way to do something in a program only when we want it to. Unchecked, program
statements will execute every time the program runs, or every time a loop runs. if works much like it does
in natural language. "if the light is on, turn it off." We don't want the light turned off if it already is. In real
life doing such a thing would cause momentary confusion. In code, it will cause errors. This is called program flow control.
Look at this example code:
int password;
cout << "Enter your password: ";
cin >> password;
if(password == 4819){
cout << "Access Granted!";
}
But what if they enter the wrong password? This is where we would use
else.
else
In C++
else cannot be used without an if preceding it. However, if
may be used by itself as we can see above. Let's add an else to our code snippet.
int password;
cout << "Enter your password: ";
cin >> password;
if(password == 4819){
cout << "Access Granted!";
}
else{
cout << "Access denied!";
}
if/else statements may be nested, meaning other if/else conditions may be placed within other if/else statements. This is where things can get very confusing very quickly. Be sure to use brackets -{ }- to open an close your statements and use proper indentation and line skipping to clearly indicate where one statement begins and the next one ends.
A nested if/else statement:
int num1 = 1;
int num2 = 2;
int num3;
if(num1 == 3){
cout << "three";
}
else{
if(num1 == 1){
num3 = num1 + num2;
cout << "three";
}
else{
cout << "Not three";
}
}
Looks dumb, but I couldn't think of anything else.
Back to our program.
At this point, if we returned the_date to the main program, we would get day number of the year (i.e., 308 for November 4th), but we want more that that. However, the number produced by the_date will be very useful to us. Our final output is going to be the day of the week and for that we need more calculations. For more calculations, we need another function. Before we start writing another function. First, let's take a step back and look at the whole program, what we have so far.
#include < stdio.h >
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Our new function will be called "get_year" and will be called from within our first function get_date. In order to figure out what day of the week a day fell on, we need to know first what the first day of a particular year was and then count up a week at a time. This is what our new function will do. Just like the first function, we will need to declare it at the top, call it from somewhere, and then create the function itself.
Continue Tutorial ----->
