C struct

In C programming, a struct (or structure) is a collection of variables (can be of different types) under a single name.

How to define structures?

Before you can create structure variables, you need to define its data type. To define a struct, the struct keyword is used.

Syntax of struct

struct structureName 
    dataType member1;
    dataType member2;

Here is an example:

struct Person
    char name[50];
    int citNo;
    float salary;

Here, a derived type struct Person is defined. Now, you can create variables of this type.

Create struct variables

When a struct type is declared, no storage or memory is allocated. To allocate memory of a given structure type and work with it, we need to create variables.

Here’s how we create structure variables:

struct Person
    char name[50];
    int citNo;
    float salary;

int main()
    struct Person person1, person2, p[20];
    return 0;

Another way of creating a struct variable is:

struct Person
    char name[50];
    int citNo;
    float salary;
} person1, person2, p[20];

In both cases, two variables person1person2, and an array variable p having 20 elements of type struct Person are created.

Access members of a structure

There are two types of operators used for accessing members of a structure.

  1. . – Member operator
  2. -> – Structure pointer operator (will be discussed in the next tutorial)

Suppose, you want to access the salary of person2. Here’s how you can do it.


Example: Add two distances

  1. // Program to add two distances (feet-inch)
  2. #include <stdio.h>
  3. struct Distance
  4. {
  5. int feet;
  6. float inch;
  7. } dist1, dist2, sum;
  8. int main()
  9. {
  10. printf("1st distance\n");
  11. printf("Enter feet: ");
  12. scanf("%d", &dist1.feet);
  13. printf("Enter inch: ");
  14. scanf("%f", &dist1.inch);
  15. printf("2nd distance\n");
  16. printf("Enter feet: ");
  17. scanf("%d", &dist2.feet);
  18. printf("Enter inch: ");
  19. scanf("%f", &dist2.inch);
  20. // adding feet
  21. sum.feet = dist1.feet + dist2.feet;
  22. // adding inches
  23. sum.inch = dist1.inch + dist2.inch;
  24. // changing to feet if inch is greater than 12
  25. while (sum.inch >= 12)
  26. {
  27. ++sum.feet;
  28. sum.inch = sum.inch - 12;
  29. }
  30. printf("Sum of distances = %d\'-%.1f\"", sum.feet, sum.inch);
  31. return 0;
  32. }Output
    1st distance
    Enter feet: 12
    Enter inch: 7.9
    2nd distance
    Enter feet: 2
    Enter inch: 9.8
    Sum of distances = 15'-5.7"

    Keyword typedef

    We use the typedef keyword to create an alias name for data types. It is commonly used with structures to simplify the syntax of declaring variables.

    This code

    struct Distance{
        int feet;
        float inch;
    int main() {
        structure Distance d1, d2;

    is equivalent to

    typedef struct Distance{
        int feet;
        float inch;
    } distances;
    int main() {
        distances d1, d2;

    Nested Structures

    You can create structures within a structure in C programming. For example,

    struct complex
     int imag;
     float real;
    struct number
       struct complex comp;
       int integers;
    } num1, num2;

    Suppose, you want to set imag of num2 variable to 11. Here’s how you can do it:

    num2.comp.imag = 11;

    Why structs in C?

    Suppose, you want to store information about a person: his/her name, citizenship number, and salary. You can create different variables namecitNo and salary to store this information.

    What if you need to store information of more than one person? Now, you need to create different variables for each information per person: name1citNo1salary1name2citNo2salary2, etc.

    A better approach would be to have a collection of all related information under a single name Person structure and use it for every person.

    More on struct

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