The solution for this month’s Exercise is perhaps a bit trickier than you may have anticipated. The issue is to set the first letter of a word as upper case and the remaining letters lowercase. The solution I devised involves reading two characters at a time.

I’m sure other solutions are possible, but for mine I created two variables: ch and prev. Both are integers, as to write a proper filter you must test for the EOF (End Of File) condition. Variable ch holds the current character and prev holds the previously-read character.

By holding two variables, you can confirm whether a letter is at the start of a word; if both prev and ch are letters, then prev must be capitalized and ch not. The only tussle is how to read the previous character when the code first runs. Here’s my solution:

#include <stdio.h>
#include <ctype.h>

int main()
{
    int ch,prev;

    /* must initialize prev */
    prev = '\0';

    /* filter loop */
    while(1)
    {
        /* fetch input */
        ch = getc(stdin);
        /* quit on EOF */
        if( ch == EOF)
            break;
        
        /* process input */
        if( isalpha(prev) )
            ch = tolower(ch);
        if( isspace(prev) || prev=='\0' || prev=='(' )
            ch = toupper(ch);

        /* send output */
        putc(ch,stdout);
        /* save current as previous character */
        prev = ch;
    }
}

Variable prev must be initialized before processing starts. Because no character is available at the beginning of input, prev is set to the null character at Line 9.

In the endless while loop, input is fetched at Line 15 and the EOF character tested at Line 17.

At Line 21, the value of character prev is tested. When isalpha() is true, prev holds a letter of the alphabet, upper or lower case. Therefore, the value of ch should be lower case, and it’s converted at Line 22.

If the previous character is a space (tab, enter, space) or null, or a beginning parentheses, the value of ch is set to uppercase at Line 24.

Line 27 sends character ch to standard output. And line 29 assigns the value of prev to the value of ch and the loop continues.

I tried to conceive of other ways to process an initial caps filter, but it just can’t be done without storing at least one character of input. For example, it’s possible to read an entire line (or buffer) and process it on output. Still, the solution I devised seems simple enough.

With C programming, no two solutions need to be the same, nor is there any one solution that’s better than the others. If you coded a solution that properly processes input and translates the words output as initial caps, great!