There is a program to compute word length of a machine as below.

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#include <stdio.h>
 
int wordlength(void);
 
int main()
{
    printf("Word Length: %dn", wordlength());  
    return 0;
}
 
int wordlength(void)
{
    int i;
    unsigned v = (unsigned)~0;
 
    for (i = 1; (v = v >> 1) > 0; ++i)
        ;
    return i;
}

Reference

The C Programming Language