A circular queue example using a keyboard buffer : Queue « Data Structure Algorithm « C / ANSI-C






  1. C / ANSI-C
  2. Data Structure Algorithm
  3. Queue

A circular queue example using a keyboard buffer

/*
C: The Complete Reference, 4th Ed. (Paperback)
by Herbert Schildt

ISBN: 0072121246
Publisher: McGraw-Hill Osborne Media; 4 edition (April 26, 2000)
*/
/* A circular queue example using a keyboard buffer. */
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>

#define MAX 80

char buf[MAX+1];
int spos = 0;
int rpos = 0;

void qstore(char q);
char qretrieve(void);

int main(void)
{
  register char ch;
  int t;

  buf[80] = '\0';

  /* Input characters until a carriage return is typed. */
  for(ch=' ',t=0; t<32000 && ch!='\r'; ++t) {
    if(_kbhit()) {
      ch = _getch();
      qstore(ch);
    }
    printf("%d ", t);
    if(ch == '\r') {
      /* Display and empty the key buffer. */
      printf("\n");
      while((ch=qretrieve()) != '\0') printf("%c", ch);
      printf("\n");
    }
  }
  return 0;
}

/* Store characters in the queue. */
void qstore(char q)
{
  if(spos+1==rpos || (spos+1==MAX && !rpos)) {
    printf("List Full\n");
    return;
  }
  buf[spos] = q;
  spos++;
  if(spos==MAX) spos = 0; /* loop back */
}

/* Retrieve a character. */
char qretrieve(void)
{
  if(rpos==MAX) rpos = 0; /* loop back */
  if(rpos==spos) return '\0';

  rpos++;
  return buf[rpos-1];
}








Related examples in the same category

1.Queue in CQueue in C