Programming in C

342 Chapter 15 Working with Larger Programs

// Date type

typedef struct date Date;

// Functions that work with dates

Date dateUpdate (Date today);

int numberOfDays (Date d);

bool isLeapYear (Date d);

// Macro to set a date in a structure

#define setDate(s,mm,dd,yy) s = (Date) {mm, dd, yy}

// External variable reference

extern Date todaysDate;

The header file defines two enumerated data types,kMonthand kDay, and the date struc-

ture (and note the use of the enumerated data types); uses typedefto create a type

called Date; and declares functions that use this type, a macro to set a date to specific val-

ues (using compound literals), and an external variable called todaysDate, that will pre-

sumably be set to today’s date (and is defined in one of the source files).

As an example using this header file, the following is a rewritten version of the

dateUpdatefunction from Chapter 9.

#include "date.h"

// Function to calculate tomorrow's date

Date dateUpdate (Date today)

{

Date tomorrow;

if ( today.day != numberOfDays (today) )

setDate (tomorrow, today.month, today.day + 1, today.year);

else if ( today.month == December ) // end of year

setDate (tomorrow, January, 1, today.year + 1);

else // end of month

setDate (tomorrow, today.month + 1, 1, today.year);

return tomorrow;

}.

Other Utilities for Working with Larger

Programs

As briefly mentioned previously, the IDE can be a powerful tool for working with larger

programs. If you still want to work from the command line, there are tools you might