第7章函数-函数调用过程机制vs程序设计方法

#include <stdio.h>
#define LowerLimit 0
#define UpperLimit 7

int Factorial(int n);

main()
{
    int i;
    for (i = LowerLimit; i <= UpperLimit; i++) {
        printf("%d! = %5d\n", i, Factorial(i));
    }
}

int Factorial(int n)
{
    int product, i;

    product = 1;
    for (i = 1; i <= n; i++) {
        product *= i;
    }
    return (product);
}

#include <stdio.h>

int Combinations(int n, int k);
int Factorial(int n);

main()
{
    int n, k;
    printf("Enter number of objects in the set (n)?  ");
    scanf("%d", &n);
    printf("Enter number to be chosen (k)?  ");
    scanf("%d", &k);
    printf("C(%d, %d) = %d\n", n, k, Combinations(n, k) );
}

int Combinations(int n, int k)
{
 return (Factorial(n) / (Factorial(k) * Factorial(n - k)));
}

int Factorial(int n)
{
    int product, i;
    product = 1;
    for (i = 1; i <= n; i++) {
	 product *= i;
    }
    return (product);
}

#include <stdio.h>

#define Sunday     0
#define Monday     1
#define Tuesday    2
#define Wednesday  3
#define Thursday   4
#define Friday     5
#define Saturday   6

typedef enum {FALSE, TRUE} bool;
typedef char *string;

void GiveInstructions(void);
int GetYearFromUser(void);
void PrintCalendar(int year);
void PrintCalendarMonth(int month, int year);
void IndentFirstLine(int weekday);
int MonthDays(int month, int year);
int FirstDayOfMonth(int month, int year);
string MonthName(int month);
bool IsLeapYear(int year);

main()
{
    int year;

    GiveInstructions();
    year = GetYearFromUser();
    PrintCalendar(year);
}

void GiveInstructions(void)
{
    printf("This program displays a calendar for a full\n");
    printf("year.  The year must not be before 1900.\n");
}

int GetYearFromUser(void)
{
    int year;

    while (TRUE) {
	printf("Which year? ");
	scanf("%d", &year);
	if (year >= 1900) return (year);
        printf("The year must be at least 1900.\n");
    }
}

void PrintCalendar(int year)
{
    int month;

    for (month = 1; month <= 12; month++) {
	 PrintCalendarMonth(month, year);
	 printf("\n");
	 getch();
    }
}

void PrintCalendarMonth(int month, int year)
{
    int weekday, nDays, day;

    printf("    %s %d\n", MonthName(month), year);
    printf(" Su Mo Tu We Th Fr Sa\n");
    nDays = MonthDays(month, year);
    weekday = FirstDayOfMonth(month, year);
    IndentFirstLine(weekday);
    for (day = 1; day <= nDays; day++) {
        printf(" %2d", day);
	if (weekday == Saturday) printf("\n");
	weekday = (weekday + 1) % 7;
    }
    if (weekday != Sunday) printf("\n");
}

void IndentFirstLine(int weekday)
{
    int i;

    for (i = 0; i < weekday; i++) {
	printf("   ");
    }
}

int MonthDays(int month, int year)
{
    switch (month) {
      case 2:
	if (IsLeapYear(year)) return (29);
	return (28);
      case 4: case 6: case 9: case 11:
	return (30);
      default:
	return (31);
    }
}

int FirstDayOfMonth(int month, int year)
{
    int weekday, i;
    weekday = Monday;
    for (i = 1900; i < year; i++) {
        weekday = (weekday + 365) % 7;
	if (IsLeapYear(i)) weekday = (weekday + 1) % 7;
    }
    for (i = 1; i < month; i++) {
	weekday = (weekday + MonthDays(i, year)) % 7;
    }
    return (weekday);
}

string MonthName(int month)
{
    switch (month) {
      case  1: return ("January");
      case  2: return ("February");
      case  3: return ("March");
      case  4: return ("April");
      case  5: return ("May");
      case  6: return ("June");
      case  7: return ("July");
      case  8: return ("August");
      case  9: return ("September");
      case 10: return ("October");
      case 11: return ("November");
      case 12: return ("December");
      default: return ("Illegal month");
    }
}

bool IsLeapYear(int year)
{
    return ( ((year % 4 == 0) && (year % 100 != 0))
	     || (year % 400 == 0) );
}