ARRAYS
(Numerical Arrays of Multiple Dimensions)
Traversing the Elements of a 2D Array
/* 3 METHODS OF MANIPULATING OF ELEMENTS OF A MATRIX*/










/* PROGRAM #80-B */
/* 3 METHODS OF MANIPULATING OF ELEMENTS OF A
MATRIX*/
#include<stdio.h>
#define
row
3
#define
column 3
main( ){
int Matrix[row][column]={ {1, 3, 5}, {7, 9, 11}, {13, 15, 17} };
int i, j, *ptr;
int *FirstElement=&Matrix[0][0];
int *LastElement=&Matrix[row-1][column-1];



}
/* METHOD 1 */







/* Use of two FOR loops, the outer loop for moving
along rows, */
/* the inner loop for moving along columns */
for(i = 0; i < row; i++)
for( j = 0; j < column; j++)
printf(“%5d”, Matrix[i][j]);
puts(“”);
/* METHOD 2 */



/* PTR is a pointer pointing to the1st element of the
matrix. This pointer gets incremented by one
through the For loop */
for(ptr = FirstElement; ptr <= LastElement; ptr++)
printf(“%5d”, *ptr);
/* METHOD 3 */







/* Showing &MATRIX[i][0] and MATRIX[i] are the
same ie, any matrix is a collection of row vectors */
/* For MATRIX[i][j], vectors can be accessed using
MATRIX[i] */
printf(“\n%d, %d\n”, &Matrix[0][0], &Matrix[1][0]);
printf(“\n%d, %d\n”, Matrix[0], Matrix[1]);
for(i = 0; i < row; i++)
for( j = 0; j < column; j++)
printf(“%5d”, *(Matrix[i]+j) );
STRINGS
STRINGS IN C
FUNCTIONS DEALING WITH
CHARACTERS
FUNCTIONS DEALING WITH STRINGS
Strings


There is no string type in C. Instead, to approximate
strings, we will use arrays of characters.
To transform a simple array of characters into a string,
it must contain the '\0‘ character in the last cell. Note
that '\0' is one character. It is called the null character
or the end-of-string character.
STRINGS IN C

String and array Similarities:

Both represent a collection of a fixed number of
elements of the same type
Elements of both array & string are located
consecutively in the memory
Name of the array is a pointer that points to the first
element of the array
Name of the string is a pointer that points to the first
element of the string



STRINGS IN C

String and array Differences:

Array represents a collection of numerical values,
Data types include int, float, double



String represents a collection of characters
Data type include only characters
String & Character:







Character: a byte of data (ASCII CODE)
char Letter='B';
/* Letter is a variable of data type char */
String:
a collection of characters
char Str[ ]="BIRDS";
/* Str is a string */
NOTE:
'A':
"A":
a single character
a string containing 2 characters, 'A' and '\0'
How to Declare a String?







1. Need to have a name for the string
2. Need to know the length of the string
3. Actual memory space needed is length of the
string + 1
(to take care of the NULL character)
4. Data type is char
Example:
char Str[20];
To declare a string and initialize it










we could do it the same way as seen before:
char city[ ] = {'T', 'o', 'r', 'o', 'n', 't', 'o', '\0'};
Notice that the size of the array can be omitted here, since the
computer can deduce it.
However, declaring the size (in this case 8), is always good
form.
But there is a simpler way:
char city[ ] = “Toronto”;
If you specify the size here, do not forget the invisible '\0'! Size
must be 8 not 7!
The result is exactly the same. By using the simpler way, the
'\0' is added automatically at the end.
'T' ' o' 'r' 'o' 'n' 't' 'o' '\0‘
01234567
“U" and ‘U'

Double quotes " " represent a string, A single quote ' ',
one character.

‘U' is the single character U But “U" is an array size 2
containing the ‘U' character and the '\0' character.

All string constants are represented in double quotes
(remember "This is my first C program." ?).
How to Initialize a String?
















/*PROGRAM # 94*/
/*DEMONSTRATES INITIALIZING STRING*/
/* length of the string is 5, need 5+1 memory space */
/* char Str[6]=”BIRDS”; */
#include <stdio.h>
main( ){
/* Declare and array with type char */
char str[ ] = "BIRDS";
printf("The string is %s.", str);
}
Note:
The format specifier for a string variable is %s.
char str [ ]="BIRDS":
declare an array named str
capable of storing characters
initialize it to "BIRDS"
Inside the Memory



char Str[6]=”BIRDS”;
char Str[ ]=”BIRDS”;
These 2 statements are equal.
Memory Map – Placement of a string
within the memory
Address
memory
Array element
2400
‘B’
Str[0]
2401
‘I’
Str[1]
2402
‘R’
Str[2]
2403
‘D’
Str[3]
2404
‘S’
Str[4]
2405
‘\0’
Str[5]
NOTES!!!

Str and &str[0] both refer to the top of the string (ie, address 2400).

‘\0’ is NULL character.

‘\0’ lets ‘C’ knows where the string ends.

When we calculate the length of the string, '\0' is NOT counted.

The length of the string is 5 but we need 6 bytes for the string (one extra
for ‘\0’).

Therefore, when declaring the string we need (LengthOfString+1) bytes.
Inside the Memory

char Str[100]="BIRDS";

is acceptable, it means that we set aside 100 bytes
in the memory for Str.

Right now we only initialize the first 6 bytes but we
expect that later on there will be some usage for the
rest of them. Furthermore, we do not have any idea
about the content of the Str[6] to str[99].
Placement of a string within the memory
Address
memory
Array element
2400
‘B’
Str[0]
2401
‘I’
Str[1]
2402
‘R’
Str[2]
2403
‘D’
Str[3]
2404
‘S’
Str[4]
2405
‘\0’
Str[5]
2406
?
Str[6]
2407
?
Str[7]
2408
?
Str[8]
…
…
…
/*DEMONSTRATES DISPLAYING
STRING*/

/* PROGRAM # 95 */

#include <stdio.h>
#define ssize 6
main( ){
char str[ ] = "BIRDS";
int i;
printf("Our string is %s. \n", str);




















/*Display characters string contains*/
puts(“Our string is made out of the following characters:”);
for(i=0; i<ssize; i++)
printf("%c\n ", str[i]);
puts(“”);
}
AFTER EXECUTION:
Our string is BIRDS.
Our string is made out of the following characters:
B
I
R
D
S