Chapter 6

 /*   File: access.c

          This program prints out the values of pointers and values of

          dereferenced pointer variables.

     */

     #include <stdio.h>

     main()

     {    int *iptr,     /* integer pointer */

               i1;

          printf("Pointers: Direct and Indirect Access\n\n");

          /* initializations */

          i1 = 10;

          iptr = &i1;    /* iptr points to the object whose name is i1 */

          /* print value of iptr, i.e., address of i1 */

          printf("iptr = %u\n", iptr);

          /* print value of the object accessed indirectly and directly */

          printf("*iptr = %d,  i1 = %d\n", *iptr, i1);

          *iptr = *iptr * 10;      /* value of *iptr changed */

          /* print values of the object again */

          printf("*iptr = %d,  i1 = %d\n", *iptr, i1);

     }

 /*   File: indincr.c

        Program illustrates indirect access

        to x by a function indirect_incr().

        Function increments x by 1.

   */

   #include <stdio.h>

   void indirect_incr(int * p);

   main()

   {    int x;

        printf("***Indirect Access***\n");

        x = 7;

        printf("Original value of x is %d\n", x);

        indirect_incr(&x);

        printf("The value of x is %d\n", x);

   }

   /*   Function indirectly accesses object in calling function.  */

   void indirect_incr(int * p)

   {

        *p = *p + 1;

   }

/*   File: pay6.c

     Other Files: payutil.c

     Header Files; tfdef.h, payutil.h

   The program gets payroll data, calculates pay, and prints out

   the results for a number of people. Modular functions are used

   to get data, calculate total pay, print data, and print results.

*/

#include <stdio.h>

#include "tfdef.h"

#include "payutil.h"

main()

{

     /* declarations */

     int id_number, moredata;

     float hours_worked, rate_of_pay, regular_pay, overtime_pay, total_pay;

     /* print title */

     printf("***Pay Calculation***\n\n");

     /* get data and initialize loop  variable */

     moredata = get_data(&id_number, &hours_worked,

                           &rate_of_pay);

     /* process while moredata */

     while (moredata) {

          total_pay = calc_pay(hours_worked, rate_of_pay, &regular_pay,

                                   &overtime_pay);

          print_data(id_number, hours_worked, rate_of_pay);

          print_pay(regular_pay, overtime_pay, total_pay);

          moredata = get_data(&id_number, &hours_worked,

                                &rate_of_pay);

     }

}

/* File: payutil.c */

#include <stdio.h>

#include "tfdef.h"

#include "payutil.h"

/* Function prints out the input data */

void print_data(int id, float hours, float rate)

{

     printf("\nID Number = %d\n", id);

     printf("Hours Worked = %f, Rate of Pay = %f\n",

               hours, rate);

}

/* Function prints pay data */

void print_pay(float regular, float overtime, float pay)

{

     printf("Regular Pay = %f, Overtime Pay = %f\n",

               regular, overtime);

     printf("Total Pay = %f\n", pay);

}

/* Function calculates and returns total pay */

float calc_pay(float hours, float rate, float * preg, float * pover)

{    float total;

     if (hours > REG_LIMIT) {

          *preg = REG_LIMIT * rate;

          *pover = OT_FACTOR * rate * (hours - REG_LIMIT);

     }

     else {

          *preg = hours * rate;

          *pover = 0;

     }

     total = *preg + *pover;

     return total;

}

/* Function reads in the payroll data */

int get_data(int * pid, float * phrs, float * prate)

{

     printf("Type ID Number, zero to quit: ");

     scanf("%d", pid);

     if (*pid <= 0)           /* if ID number is <= 0, */

          return FALSE;       /* return 0 to calling function */

     printf("Hours Worked: "); /* ID number is valid, get data */

     scanf("%f", phrs);

     printf("Hourly Rate: ");

     scanf("%f", prate);

     return TRUE;             /* valid data entered, return 1 */

}

     /* File: payutil.h */

     #define REG_LIMIT 40

     #define OT_FACTOR 1.5

     int get_data(int *pid, float *phrs, float *prate);

     void print_data(int id, float hrs, float rate);

     void print_pay(float regular, float overtime, float total);

     float calc_pay(float hours, float rate, float * pregular,

                         float * povertime);

/*   File: sqcube.c

          Program uses a function that returns a square of its argument and

          indirectly stores the cube.

     */

     #include <stdio.h>

     double sqcube(double x, double * pcube);

     main()

     {    double x, square, cube;

          printf("***Directly and Indirectly Returned Values***\n");

          x = 3;

          square = sqcube(x, &cube);

          printf("x = %f, square = %f, cube = %f\n",

                    x, square, cube);

     }

     /* Function return square of x, and indirectly stores cube of x */

     double sqcube(double x, double * pcube)

     {

          *pcube = x * x * x;

          return (x * x);

     }

 /*   File: swapfnc.c

          Program uses a function to swap values of two objects.

     */

     #include <stdio.h>

     /* arguments of swap() are integer pointers */

     void swap(int * p1, int * p2);

     main()

     {    int dat1 = 100, dat2 = 200;

          printf("Original values: dat1 = %d, dat2 = %d\n", dat1, dat2);

          swap(&dat1, &dat2);

          printf("Swapped values: dat1 = %d, dat2 = %d\n", dat1, dat2);

     }

     /*  Function swaps values of objects pointed to by ptr1 and ptr2 */

     void swap(int * ptr1, int * ptr2)

     {    int temp;

          temp = *ptr1;

          *ptr1 = *ptr2;

          *ptr2 = temp;

     }

/* File: tfdef.h */

#define TRUE 1

#define FALSE 0