Programming

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>

/*Print a char twice like putchar, return char if successful, or EOF on error.*/

int putcharTwice(int c)
{
    if (putc(c, stdout) == EOF || putc(c, stdout) == EOF)  {//Q1
    return EOF;
    } else {
    return 0;        //NOT return c;
    }
}

#define NUM_CHARS (UCHAR_MAX + 1)    //UCHAR_MAX is in limits.h

  int (*table[NUM_CHARS]) (int);   //Q2, So moved outside main() to see this function pointer

int main(int argc, char **argv)
{
/*This declares table as array of function pointers */
    int i;
    int c;

    for (i = 0; i < UCHAR_MAX; i++) {
    // default is to call putchar 
    table[i] = putchar;
    }

    // but lower-case vowels show up twice 
    table['a'] = putcharTwice; //Q3, and following 4 lines
    table['e'] = putcharTwice; //Q3
    table['i'] = putcharTwice; //Q3
    table['o'] = putcharTwice; //Q3
    table['u'] = putcharTwice; //Q3

    while ((c = getchar()) != EOF) {
    table[c] (c); //Q4,
    }
    return 0;
}