c_ch01_ex14.c

/*
 * Exercise 1-14.
 * Write a program to print a histogram of the
 * frequencies of different characters in its input.
 */

#include <stdio.h>

#define	CHARCOUNT 52
#define	HWIDTH 80


main() {
	int c, chrs[CHARCOUNT], i;
	int count, max;


	/* initialize the histogram and max */
	for (i = 0; i < CHARCOUNT; i++)
		chrs[i] = 0;
	max = 0;

	/* populate the histogram */
	while ((c = getchar()) != EOF) {
		if (c >= 'a' && c <= 'z') {
			++chrs[c - 'a'];
		} else if (c >= 'A' && c <= 'Z') {
			++chrs[c - 'A' + 26];
		}
	}

	/* calculate max */
	for (i = 0; i < CHARCOUNT; i++)
		if (chrs[i] > max)
			max = chrs[i];

	/* draw the histogram */
	for (i = 0; i < CHARCOUNT; i++) {
		if (chrs[i]) {
			/* is it a small character */
			if (i < 26)
				c = i + 'a';
			else
				c = i - 26 + 'A';

			printf("[%c] ", c);
			for (count = 0; count < (chrs[i]*HWIDTH)/max; count++)
				putchar('@');
			for (count = 0;
				count < HWIDTH - (chrs[i]*HWIDTH)/max; count++)
				putchar(' ');
			printf(" %6d\n", chrs[i]);
		}
	}

}