A9 - derived data types

arrays

array

a collection of values with the same time, represented by a single name, and an index that allows the selection of individual members

type array_name[array_length] = {elememnt1, element2};
 
 int arr[5] = {1, 2, 3, 4, 5};
 
 int arr_2D[3][2] = {1, 2}, 
				{3, 4}, 
				{5, 6};

pointer

a type, whose value is the address of another variable

#include <stdio.h>

int main ()
{
	float var1 = 5;
	float *p = &var1; /* points to var1 */
	
	printf("%f\n", p); /* address of pointer p */
	printf("%f\n", *p); /* value of pointer p */
}

function

a group of instructions to perform a given task

#include <stdio.h>
#include <stdint.h>

/* function declaration */
int calculateSum(int x, int y);

int main ()
{
	int calc = calculateSum(1, 2);
	print("%d\n", calc);
}

/* function implementation */
int calcualteSum(int x, int y)
{
	return x + y;
}

structure

a collection of variables of possibly different types, into a single user defined type

struct address {
	char name[100];
	char street[100];
	char city[50];
	int pin;
}

struct address add1 = {"abode", "this street", "that town", 12345}; /* assign values */

add1.name = "residence" /* edit a value */

int num = add1.pin /* access a value */

// access using a pointer
struct address add2;             /* define a new address */
add2_ptr = &add2;               /* assign a pointer for the structure */
add2_ptr->name = 'work'  /* assign values */

union

a collection of variables of possibly different types into a single user defined type, stored in the same memory location

only one property can be initialised at a time

union address {
	char name[100];
	char street[100];
	char city[50];
	int pin;
}

union address add1 = {"abode"};
strcpy(add1.street, "this street");