C Programming Code Examples

C > Beginners Lab Assignments Code Examples

A simple mailing list using an array of structures



A simple mailing list using an array of structures

#include <stdio.h>
#include <stdlib.h>

#define MAX 100

struct addr {
  char name[25];
  char street[50];
  char city[25];
  char state[3];
  unsigned long int zip;
} addr_list[MAX];

void init_list(void), enter(void);
void delete(void), list(void);
int menu_select(void), find_free(void);

int main(void)
{
  char choice;

  init_list(); /* initialize the structure array */
  for(;;) {
    choice = menu_select();
    switch(choice) {
      case 1: enter();
        break;
      case 2: delete();
        break;
      case 3: list();
        break;
      case 4: exit(0);
    }
  }

  return 0;
}

/* Initialize the list. */
void init_list(void)
{
  register int t;

  for(t=0; t<MAX; ++t) addr_list[t].name[0] = '\0';
}

/* Get a menu selection. */
int menu_select(void)
{
  char s[100];
  int c;

  printf("1. Enter a name\n");
  printf("2. Delete a name\n");
  printf("3. List the file\n");
  printf("4. Quit\n");
  do {
    printf("\nEnter your choice: ");
    gets(s);
    c = atoi(s);
  } while(c<0 || c>4);
  return c;
}

/* Input addresses into the list. */
void enter(void)
{
  int slot;
  char s[100];

  slot = find_free();

  if(slot==-1) {
    printf("\nList Full");
    return;
  }

  printf("Enter name: ");
  gets(addr_list[slot].name);

  printf("Enter street: ");
  gets(addr_list[slot].street);

  printf("Enter city: ");
  gets(addr_list[slot].city);

  printf("Enter state: ");
  gets(addr_list[slot].state);

  printf("Enter zip: ");
  gets(s);
  addr_list[slot].zip = strtoul(s, '\0', 10);
}

/* Find an unused structure. */
int find_free(void)
{
  register int t;

  for(t=0; addr_list[t].name[0] && t<MAX; ++t) ;

  if(t==MAX) return -1; /* no slots free */
  return t;
}

/* Delete an address. */
void delete(void)
{
  register int slot;
  char s[100];

  printf("enter record #: ");
  gets(s);
  slot = atoi(s);

  if(slot>=0 && slot < MAX)
    addr_list[slot].name[0] = '\0';
}

/* Display the list on the screen. */
void list(void)
{
  register int t;

  for(t=0; t<MAX; ++t) {
    if(addr_list[t].name[0]) {
      printf("%s\n", addr_list[t].name);
      printf("%s\n", addr_list[t].street);
      printf("%s\n", addr_list[t].city);
      printf("%s\n", addr_list[t].state);
      printf("%lu\n\n", addr_list[t].zip);
    }
  }
  printf("\n\n");
}