Pointers and Arrays

Pointer

•Pointer is a variable that store the address of another variable

•Syntax :

  <type> *ptr_name;

•Two operators mostly used in pointer : * (content of) and & (address of)

Pointer to Pointer

•Pointer to pointer is a variable that saves another address of a pointer

•Syntax:

  <type> **ptr_ptr ;

Array

•Data saved in a certain structure to be accessed as a group or individually. Some variables

saved using the same name distinguish by their index.

•Syntax:

  type array_value [value_dim];

Array Initialization

•Array can be initialized explicitly without dimensional value declaration

Accessing Arrays

•Two analogous ways of accessing an element i=2;

  *(A+2) or A[2]

•A  is equivalent with &A[0] or a constant pointer to the first element of particular array

•To show A[2] on the monitor screen:

  printf(“%d”,A[2]) or

  printf(“%d\n”,*(A+2));

Pointer Constant & Pointer Variable

•Pointer variable is a pointer that can be assigned with new value at run-time.

•Pointer constant is a pointer that can not be assigned with new value at run-time

•Array is Pointer Constant to its first element of the array. Array can be filled with pointer variable.

One Dimensional Array

•Syntax 1D Array:

  type name_array[row];

Two Dimensional Array

•Syntax 2D Array:

type name_array[row][col];

Three Dimensional Array

•Syntax 3D Array :

type name_array[row][col][depth];

Array of Pointer

•An array filled with pointer/s

•Syntax :

type *array_name [value_dim];

Array of Character

•Array filled with character/s

•Syntax:

char array_name[value_dim];

String

•String is an array of character that ended with null character ( ‘\0’ or in ASCII = 0)

String Manipulation

•Types of function to manipulate string in string.h library

– strlen()

Return a value of string length; excluded null char

– strcpy(statement1, statement2)

Copy statement2 to statement1

– strncpy(statement1, statement2,n)

Copy first n characters of statement2 to statement1

– strcat(statement1, statement2)

Adding string statement2 to the end of string statement1

– strncat(statement1, statement2,n)

Adding n characters of string statement2 to the end of string statement1

– strcmp(statement1, statement2)

Comparing the value of string statement1 and statement2, if similar returning 0

– etc.

Repetition

Repetition

·One or more instruction repeated for certain amount 

of time

·Repetition/looping operation:

– For

– While

– Do-while

             1. For

•Syntax:

for(exp1; exp2; exp3) statement;

or:

for(exp1; exp2; exp3){

  statement1;

  statement2;

  …….

 }

exp1 :  initialization

exp2 :  conditional

exp3 :  increment or decrement

exp1, exp2 and exp3 are optional

EXAMPLE :

Program to print out numbers from 1 to 10

     #include<stdio.h>

int main()

{

    int x;

    for( x = 1 ;  x <= 10 ;  x++ ) printf( "%d\n", x );

    return(0);

}

      2. While

•Syntax :

while (exp) statements;

or:

while(exp){

  statement1;

  statement2;

   …..

}

EXAMPLE :

int counter = 1;

while ( counter <= 10 ) {

     printf( "%d\n", counter );

     ++counter;

}

3. Do-While

•Syntax :

do{

    < statements >;

} while(exp);

•Keep executing while exp is true

•exp evaluation done after executing the statement(s)

EXAMPLE :

int counter=0;

do {

     printf( "%d  ", counter );

  ++counter;

} while (counter <= 10);