Arrays

Arrays

Let us write a program to count the number of occurrences of each digit, of white space characters (blank, tab,
newline), and of all other characters. This is artificial, but it permits us to illustrate several aspects of C in one
program.
There are twelve categories of input, so it is convenient to use an array to hold the number of occurrences of each
digit, rather than ten individual variables. Here is one version of the program:

#include <stdio.h>
/* count digits, white space, others */
main()
{
int c, i, nwhite, nother;
int ndigit[10];
nwhite = nother = 0;
for (i = 0; i < 10; ++i)
ndigit[i] = 0;
while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9')
++ndigit[c-'0'];
else if (c == ' ' || c == '\n' || c == '\t')
++nwhite;
else
++nother;
printf("digits =");
for (i = 0; i < 10; ++i)
printf(" %d", ndigit[i]);
printf(", white space = %d, other = %d\n",
nwhite, nother);

}
The output of this program on itself is
digits = 9 3 0 0 0 0 0 0 0 1, white space = 123, other = 345
The declaration
int ndigit[10];
declares ndigit to be an array of 10 integers. Array subscripts always start at zero in C, so the elements are
ndigit[0], ndigit[1], ..., ndigit[9]. This is reflected in the for loops that initialize and print
the array.
A subscript can be any integer expression, which includes integer variables like i, and integer constants.
This particular program relies on the properties of the character representation of the digits. For example, the test
if (c >= '0' && c <= '9')
determines whether the character in c is a digit. If it is, the numeric value of that digit is

c - '0'
This works only if '0', '1', ..., '9' have consecutive increasing values. Fortunately, this is true for all
character sets.
By definition, chars are just small integers, so char variables and constants are identical to ints in arithmetic
expressions. This is natural and convenient; for example c-'0' is an integer expression with a value between 0
and 9 corresponding to the character '0' to '9' stored in c, and thus a valid subscript for the array ndigit.
The decision as to whether a character is a digit, white space, or something else is made with the sequence
if (c >= '0' && c <= '9')
++n digit[c-'0'];
else if (c == ' ' || c == '\n' || c == '\t')
++n white;
else
++n other;
The pattern
if (condition 1)
statement 1
else if (condition 2)
statement 2
...
...
else

statement n
occurs frequently in programs as a way to express a multi-way decision. The conditions are evaluated in order
from the top until some condition is satisfied; at that point the corresponding statement part is executed, and the
entire construction is finished. (Any statement can be several statements enclosed in braces.) If none of the
conditions is satisfied, the statement after the final else is executed if it is present. If the final else and
statement are omitted, as in the word count program, no action takes place. There can be any number of
else if(condition)
statement
groups between the initial if and the final else.
As a matter of style, it is advisable to format this construction as we have shown; if each if were indented past the

previous else, a long sequence of decisions would march off the right side of the page.

Also Read:

• The first C programme.

• The Grammer Of C

• Program in C to find Cubic sum of a number

• Program to make number pattern

• Palindrome in C

• Prime Number Series

• C PROGRAM TO DISPLAY FIBONACCI SERIES

• Lucas Series

• Even Or ODD

• Greater of Two

• If Else in C

• Else If In C

• Switch

• Example For Switch Case

• Print without printf in C

• Functions