Structure pointer example

This example shows the use of pointers to structures and pointer arithmetic.

The code includes 4 different ways of printing a struct array. All these ways give the same result. Which one to use depends on the needs as well as personal preferences and team requirements.

Some notes for comparing this code to the square bracket array notation:

In PrintEmployees1() , you could use pEmployees[i].member instead.
In PrintEmployees3() , you could pass pEmployees[i] instead (but not pEmployee[i] ).

/**
 * File:            struct_pointers.c
 * Author:          Risto Heinsar
 * Created:         25.02.2015
 * Modified:        13.02.2024
 *
 * Descriptions:    A longer sample for passing structures to functions and
 *                  using pointers to access them. This code contains multiple
 *                  ways to achieve the same goal.
 */

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

#define N 20

typedef struct employee
{
    int employeeCode;
    char fName[N];
    char lName[N];
    float wage;
} employee;

void PrintEmployee(employee *pEmployee);
void PrintEmployees1(employee *pEmployees, int n);
void PrintEmployees2(employee *pEmployees, int n);
void PrintEmployees3(employee *pEmployees, int n);
void PrintEmployees4(employee *pEmployees, int n);

int main(void)
{
    employee manager = {75, "Indrek", "Tamm", 12.75f};
    employee staff[] = {{20, "Toomas", "Vali",  5.22f},
                        {23, "Madis",  "Mets",  4.21f},
                        {25, "Kaspar", "Kuusk", 3.25f}};
    

    // Prints a single employee records
    PrintEmployee(&manager);
    putchar('\n');

    // Calculate number of employees in the array
    int n = sizeof(staff) / sizeof(employee);
    
    // 3 different ways of printing employee data
    PrintEmployees1(staff, n);
    PrintEmployees2(staff, n);
    PrintEmployees3(staff, n);
    PrintEmployees4(staff, n);

    return EXIT_SUCCESS;
}


/**
 * Description: Prints the records of a single employee
 * 
 * Parameters:  pEmployee - pointer to employee data
 * Return:      none
 */
void PrintEmployee(employee *pEmployee)
{
    printf("Employee %06d, %s %s makes %2.2f in an hour\n", 
            pEmployee->employeeCode, 
            pEmployee->fName, 
            pEmployee->lName,
            pEmployee->wage);
}


/**
 * Description: This is an example print function that prints all employee data
 *              using pointer arithmetic to index the struct array. Prinding is
 *              done directly.
 * 
 * Parameters:  pEmployee - pointer to employee data
 *              n - number of employees
 * Return:      none
 */
void PrintEmployees1(employee *pEmployees, int n)
{
    for (int i = 0; i < n; i++)
    {
        printf("Employee %06d, %s %s makes %2.2f in an hour\n", 
                (pEmployees + i)->employeeCode, 
                (pEmployees + i)->fName,
                (pEmployees + i)->lName, 
                (pEmployees + i)->wage);
    }
    putchar('\n');        
}


/**
 * Description: This is very similar to PrintEmployees1(), but in this case 
 *              we are incrementing the the copy of the pointer address.
 * 
 * Parameters:  pEmployee - pointer to employee data
 *              n - number of employees
 * Return:      none
 */
void PrintEmployees2(employee *pEmployees, int n)
{
    // Store pointer to the first member separately (for clarity)
    employee *pEmployee = pEmployees;
    
    for(int i = 0; i < n; i++)
    {
        
       /* Print the current employee */
        printf("Employee %06d, %s %s makes %2.2f in an hour\n", 
                pEmployee->employeeCode, 
                pEmployee->fName,
                pEmployee->lName, 
                pEmployee->wage);
                
        /* Move the employee pointer to the next struct member (employee) */
        pEmployee++;
    }
    putchar('\n');
}


/**
 * Description: This is very similar to PrintEmployees1(), but in this case 
 *              we are using an exisitng print function to handle printing.
 *              Useuful if you need to print the same data in multiple places.
 * 
 * Parameters:  pEmployee - pointer to employee data
 *              n - number of employees
 * Return:      none
 */
void PrintEmployees3(employee *pEmployees, int n)
{
    // Store pointer to the first member separately (for clarity)
    employee *pEmployee = pEmployees;
    
    for(int i = 0; i < n; i++)
    {
        /* Print the current employee */
        PrintEmployee(pEmployee);
                
        /* Move the employee pointer to the next struct member (employee) */
        pEmployee++;
    }
    putchar('\n');
}

/**
 * Description: This is again the in same notion as the previous examples,
 *              but this time we make a dedicated pointer to an employee
 *              struct in the loop, offering even cleaner code
 * 
 * Parameters:  pEmployee - pointer to employee data
 *              n - number of employees
 * Return:      none
 */
void PrintEmployees4(employee *pEmployees, int n)
{
    for(int i = 0; i < n; i++)
    {
        /* Select the employee from the struct pointer array */
        employee *pEmployee = pEmployees + i;
        
        /* Print the current employee */
        PrintEmployee(pEmployee);
    }
    putchar('\n');
}

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/**

* File: struct_pointers.c

* Author: Risto Heinsar

* Created: 25.02.2015

* Modified: 13.02.2024

* Descriptions: A longer sample for passing structures to functions and

* using pointers to access them. This code contains multiple

* ways to achieve the same goal.

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#define N 20

typedef struct employee

{

int employeeCode;

char fName[N];

char lName[N];

float wage;

} employee;

void PrintEmployee(employee *pEmployee);

void PrintEmployees1(employee *pEmployees, int n);

void PrintEmployees2(employee *pEmployees, int n);

void PrintEmployees3(employee *pEmployees, int n);

void PrintEmployees4(employee *pEmployees, int n);

int main(void)

{

employee manager = {75, "Indrek", "Tamm", 12.75f};

employee staff[] = {{20, "Toomas", "Vali", 5.22f},

{23, "Madis", "Mets", 4.21f},

{25, "Kaspar", "Kuusk", 3.25f}};

// Prints a single employee records

PrintEmployee(&manager);

putchar('\n');

// Calculate number of employees in the array

int n = sizeof(staff) / sizeof(employee);

// 3 different ways of printing employee data

PrintEmployees1(staff, n);

PrintEmployees2(staff, n);

PrintEmployees3(staff, n);

PrintEmployees4(staff, n);

return EXIT_SUCCESS;

}

/**

* Description: Prints the records of a single employee

* Parameters: pEmployee - pointer to employee data

* Return: none

void PrintEmployee(employee *pEmployee)

{

printf("Employee %06d, %s %s makes %2.2f in an hour\n",

pEmployee->employeeCode,

pEmployee->fName,

pEmployee->lName,

pEmployee->wage);

}

/**

* Description: This is an example print function that prints all employee data

* using pointer arithmetic to index the struct array. Prinding is

* done directly.

* Parameters: pEmployee - pointer to employee data

* n - number of employees

* Return: none

void PrintEmployees1(employee *pEmployees, int n)

{

for (int i = 0; i < n; i++)

{

printf("Employee %06d, %s %s makes %2.2f in an hour\n",

(pEmployees + i)->employeeCode,

(pEmployees + i)->fName,

(pEmployees + i)->lName,

(pEmployees + i)->wage);

}

putchar('\n');

}

/**

* Description: This is very similar to PrintEmployees1(), but in this case

* we are incrementing the the copy of the pointer address.

* Parameters: pEmployee - pointer to employee data

* n - number of employees

* Return: none

void PrintEmployees2(employee *pEmployees, int n)

{

// Store pointer to the first member separately (for clarity)

employee *pEmployee = pEmployees;

for(int i = 0; i < n; i++)

{

/* Print the current employee */

printf("Employee %06d, %s %s makes %2.2f in an hour\n",

pEmployee->employeeCode,

pEmployee->fName,

pEmployee->lName,

pEmployee->wage);

/* Move the employee pointer to the next struct member (employee) */

pEmployee++;

}

putchar('\n');

}

/**

* Description: This is very similar to PrintEmployees1(), but in this case

* we are using an exisitng print function to handle printing.

* Useuful if you need to print the same data in multiple places.

* Parameters: pEmployee - pointer to employee data

* n - number of employees

* Return: none

void PrintEmployees3(employee *pEmployees, int n)

{

// Store pointer to the first member separately (for clarity)

employee *pEmployee = pEmployees;

for(int i = 0; i < n; i++)

{

/* Print the current employee */

PrintEmployee(pEmployee);

/* Move the employee pointer to the next struct member (employee) */

pEmployee++;

}

putchar('\n');

}

/**

* Description: This is again the in same notion as the previous examples,

* but this time we make a dedicated pointer to an employee

* struct in the loop, offering even cleaner code

* Parameters: pEmployee - pointer to employee data

* n - number of employees

* Return: none

void PrintEmployees4(employee *pEmployees, int n)

{

for(int i = 0; i < n; i++)

{

/* Select the employee from the struct pointer array */

employee *pEmployee = pEmployees + i;

/* Print the current employee */

PrintEmployee(pEmployee);

}

putchar('\n');

}