1. 
        cp = c;
illegal, must assign an address to cp

        cp = &c;
legal, assign variable c's address to cp

        *cp = &c;
illegal, cannot copy/store the address to where cp points to

        cp = &a;
illegal, a's address is the address of a[0], &a does not make any sense.
        cp is also a char pointer

        &cp = c;
illegal, cannot assign a value to the address of anything

        &cp = &c;
illegal, same as above

        ip = &a;
illegal, a can be used for its address, which is &a[0], no need to have &

        ip = a;
legal, assign the address of array a, which is &a[0], to ip

        ip = &a[0];
legal, same as above

        (ip = a) + n;
legal, assign the address of array a to ip and then return the address of
        a[2]. note that n=2

        *((ip=a)+n) = 5;
legal, assign the address of array a to ip and then store value 5 to a[2]

2.
#defind ELEMENTS 20     // assume that we will read in 20 numbers

float *read_array(void)
{
        int      count;
        static float    array[ELEMENTS];
/* NOTE use of static array as we are returning its address */

        for(count = 0; count<ELEMENTS; count++)
        {
                printf(" Please enter the value for element %2d : ",count);
                scanf("%f", &array[count]);
        }

        return array;
}

3.
        p1 = &b;
p1 assigned the address of constant char variable

        p1 = &a;
p1 assigned the address of char variable

        p2 = &a;
p2 assigned the address of char variable

        p2 = &b;
ILLEGAL. cannot assign p2 the address of constant char variable

        *p1 = '$';
ILLEGAL. p1 points to constant char variable, value cannot be re-assigned

        *p2 = '$';
the address that p2 points to now stores char '$'

        p1 = p2;
p1 assigned the address that p2 points to

        p2 = p1;
ILLEGAL. cannot the address of p1, a pointer to constant char, to p2

4.
   1) a[] = {10,20}, x = 25
left = 0, right = 2: check = 1, a[1] < 25
left = check + 1 = 2, right = 2: check = 2, now access a[2], wrong.

   2) a[] = {10, 20}, x = 20
left = 0, right = 1: check = 0, a[0] < 20
left = check + 1 = 1, right = 1: will not check a[1] and report not found.

   3) a[] = {10, 20}, x = 20
left = 0, right = 1: check = 0, a[0] < 20
left = check + 1 = 1, right = 1: check = 0, a[0] < 20
left = check + 1 = 2, right = 1: left > right, stop and report not found.

   4) a[] = {10, 20}, x = 20
left = 0, right = 1: check = 0, a[0] < 20
left = check  = 0, right = 1: check = 0, stays in the while loop infinitely.

5. 
#include<stdio.h>
#include<string.h>

int main()
{
        int correctDay = 0;
        char *day;
        int i=0;

        do
        {
                day= (char *) malloc(sizeof(char));
                printf("Enter a day of the week (Sun, Mon, Tues, Wednes, Thurs, Fri, or Satur):");
                i=0;
                do
                {
                        scanf("%c",&day[i]);
                        i++;
                        day=(char *)realloc(day,sizeof(char)*(i+1));
                }while(day[i-1]!='\n');
// read in the input

                day[i-1]='\0'; 
// put \0 so we can do string operation later

                day=(char *)realloc(day,sizeof(char)*i);
// this reduces the size of day by 1 sizeof(char).
// It does not affect the correctness

                if(!strcmp(day,"Sun")|| !strcmp(day,"Mon")||!strcmp(day,"Tues")||!strcmp(day,"Wednes") ||!strcmp(day,"Thurs")||!strcmp(day,"Fri") ||!strcmp(day,"Satur"))
                {
                        printf("Today is %s",day);
                        printf("day.\n");
                        correctDay=1;
                }
                free(day);
        }while(correctDay!=1);
// the outer do-while loop keeps on asking for input until a valid
// day is entered.

        return 0;
}


6. 
#include<stdio.h>

int main()
{
        int a1=0;
        int b1=0;
        int a2=0;
        int b2=0;

        printf("Please enter value of a1 and b1 (with a space between their values):");
        scanf("%d %d",&a1,&b1);
        printf("Please enter value of a2 and b2 (with a space between their values):");
        scanf("%d %d",&a2,&b2);
        if(a1<a2 || (a1 == a2 && b1 < b2 ))
        {
                printf("(%d %d) (%d %d)\n",a1,b1,a2,b2);
        }
        else
        {
                printf("(%d %d) (%d %d)\n",a2,b2,a1,b1);
        }
        return 0;

}

7. 
#include<stdio.h>

int main()
{
        int imax=0, imin=0, *p;
// imax and imin are the indices for the max and min item in the list
        int i=0,j;

        printf("Enter a list of integers:");
        p = (int *) malloc(sizeof(int));

        do
        { scanf("%d",&p[i]);
          if ( p[imax] < p[i]) imax = i;
          if ( p[imin] > p[i]) imin = i;
          i++;
          p =(int *)realloc(p, sizeof(int)*(i+1));
// get ready for next integer
        }while(getchar() != '\n');

        for (j=0; j<i; j++)
        { if (j == imax || j == imin )
                continue;
          printf("%d ", p[j]);
        }

        putchar('\n');
        free(p);

        return 0;
}