Syntax for lab 5

Key syntax elements for lab 5

The C++ features we will add for lab 5 are structs (plus arrays of structs) and char arrays with cin.getline, strcpy, strcmp, and strlen. (Refer back to the course notes or to the previous labs for refreshers on the syntax used earlier.)

Structs and arrays of structs

Declaring a struct data type, typically in the global definitions section of our programs, after the global constant definitions but before function prototypes

// declare a data type to represent time,
//    with ints for hours and minutes,
//    and a float for seconds (0-59.9999)
struct Time {
   int hour;     // 0-23
   int minute;   // 0-59
   float second; // 0-59.9999
};

Initializing variables of a struct type

Time startTime = { 11, 30, 0.00 };  // sets hour, minute, and seconds

Accessing the fields of a struct variable using the variable.field notation

   startTime.hour = 9;
   startTime.minute = 20;
   startTime.second =  0.01;
   printf("Start time is %02d:%02d:%05.2f\n", startTime.hour, startTime.minute, startTime.second);

Using a function to set the fields of a struct (i.e. pass by reference)

// sets time to 00:00:00
void setTime(Time &T);

int main()
{
   Time t;
   setTime(t);
}

void setTime(Time &T)
{
   T.hour = 0;
   T.minute = 0;
   T.second = 0;
}

Declaring and using an array of structs:

int main()
{
    const int size = 10;
    Time timevals[size]; // creating the array

    // filling it one element at a time with calls to setTime
    for (int i = 0; i < size; i++) {
        setTime(timevals[i]);
    }

    // accessing the elements directly through the array
    for (int j = 0; j < size; j++) {
        cout << "Hour: ";
        cout << timevals[j].hour; // the hour field of the j'th element
        cout << ", minute: ";
        cout << timevals[j].minute; // the minute field of the j'th element
        cout << endl;
    }
}

Key syntax elements for lab 5

Structs and arrays of structs

Character arrays with cstdio, cout, cin.getline