C Structures

A structure is used to group different types of data together. It is defined using the struct keyword.

Syntax

struct Name{
  type1 memberName1;
  type2 memberName2;
  type3 memberName3;
  ...
  typeN memberNameN;
};

A structure is made up of members where each memberName has to be declared with a type.

Example

The following example uses the struct keyword to create a Patient structure:

struct Patient{
  char name[30];
  int age;
  int weight;
  int heightInInches;
};

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name, age, weight, and heightInInches are members of the Patient structure.

Structure Variables

Variables can be created in order to work with the Patient structure above. The following example declares and initializes a structure variable:

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

struct Patient {
  char name[30];
  int age;
  int weight;
  int heightInInches;
};

int main() {
  // Variable initialization at declaration
  struct Patient patientA = {"Douglas Franklin", 62, 280, 74};
  return 0;
}

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Accessing Members

Members can be accessed using the member operator .:

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

struct Patient {
  char name[30];
  int age;
  int weight;
  int heightInInches;
};

int main() {
  // Variable initialization at declaration
  struct Patient patientA = {"Douglas Franklin", 62, 280, 74};

  // Accessing members
  printf("Name: %s \nAge: %d \nWeight: %d \nHeight: %d\n",
        patientA.name, patientA.age, patientA.weight, patientA.heightInInches);

  return 0;
}

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This will output the following:

Name: Douglas Franklin
Age: 62
Weight: 280
Height: 74

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Nested Structures

A structure can be within another structure. Nested structure members can be accessed using the member operator .. The example below shows a Hospital structure member variable being declared within the Patient structure:

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

struct Hospital {
  char department[30];
  int roomNum;
};

struct Patient {
  char name[30];
  int age;
  int weight;
  int heightInInches;
  struct Hospital roomDetails;
};

int main() {
  // Variable initialization at declaration
  struct Patient patientA = {"Douglas Franklin", 62, 280, 74, "oncology", 526};

  // Accessing nested structure members
  printf("Department: %s \nRoom: %d \n", patientA.roomDetails.department, patientA.roomDetails.roomNum);

  return 0;
}

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The output is as follows:

Department: oncology
Room: 526

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