PROBLEM 1:
runner% cat exam1_3.c
#include <stdio.h>
#define MAXA 100
struct atag {
    char ch;
    int num;
};

void init(struct atag a[]);
int addup(struct atag a[]);

void main(void)
{
   struct atag a[MAXA];
   int sum;
   init(a);
   sum = addup(a);
   printf("sum: %i\n", sum);
}

void init(struct atag a[])
{
   int i;
   for (i = 0; i < MAXA; i++) {
      a[i].ch = ' ';
      a[i].num = i;
   }
}

int addup(struct atag a[])
{
   int i;
   int sum = 0;
   for (i = 0; i < MAXA; i++)
      sum += a[i].num;
   return sum;
}

PROBLEM 2:
runner% exam1_3
sum: 4950

runner% cat -n exam1_2.c
     1  #include <stdio.h>
     2  
     3  void main(void)
     4  {
     5     char t[] = "UTSA";
     6     char *p;
     7     char *q;
     8     p = t;
     9     
    10     printf("Printing t:        %s\n", t);
    11     printf("Printing p:        %s\n", p);
    12     printf("Printing t[0]:     %c\n", t[0]);
    13     printf("Printing t[1]:     %c\n", t[1]);
    14     printf("Printing *p:       %c\n", *p);
    15     printf("Printing &t[0]:    %s\n", &t[0]);
    16     printf("Printing *(p+2):   %c\n", *(p+2));
    17     printf("Printing p+2:      %s\n", p+2);
    18     printf("Printing *&p:      %s\n", *&p);
    19     printf("Printing &t:       %c\n", &t);    /* ERROR */
    20     printf("Printing &t[1]:    %s\n", &t[1]);
    21     printf("Printing &q[0]:    %c\n", &q[0]); /* ERROR */
    22  }
runner% lint -m -u exam1_2.c
(21) warning: variable may be used before set: q

function returns value which is always ignored
    printf          

function argument ( number ) type inconsistent with format
    printf (arg 2)      char (*)[] :: (format) int      exam1_2.c(19)
    printf (arg 2)      char * :: (format) int  exam1_2.c(21)
runner% cc -o exam1_2 exam1_2.c
runner% exam1_2
Printing t:        UTSA
Printing p:        UTSA
Printing t[0]:     U
Printing t[1]:     T
Printing *p:       U
Printing &t[0]:    UTSA
Printing *(p+2):   S
Printing p+2:      SA
Printing *&p:      UTSA
Printing &t:       
Printing &t[1]:    TSA
Printing &q[0]:    

PROBLEM 3:
runner% cat exam1_4.c
#include <stdio.h>
#include "stack.h"

void pop_and_print1(void);
void pop_and_print2(void);

void main(void)
{
   char ch;
   while (((ch = getchar()) != '\n') && !full())
      push(ch);
   /* pop_and_print1(); putchar('\n'); */
   pop_and_print2(); putchar('\n');
}

void pop_and_print1(void)
{
   while (!empty())
      putchar(pop());
}

void pop_and_print2(void)
{   
   char ch;
   if (!empty()) {
      ch = pop();
      pop_and_print2();
      putchar(ch);
   }
}
runner% cc -o exam1_4 exam1_4.c stack.c
exam1_4.c:
stack.c:
runner% exam1_4
abcd
abcd