1. Week 8 Arrays Part 2 String & Pointer
Sem1-06/07
EKT120: Computer Programming

2. EKT120: Computer Programming
Outline
Passing Array to Function
Print the Array
How Arrays are passed in a function call
Introduction to Strings
String Type
Character Array
Declaration of Strings
Fundamentals of Strings & Characters
Initialization of Strings
Assigning Values to Strings
Calculation of String Size
String Conversion Functions
Comparison Functions of the Strings
ASCII Table
Sem1-06/07
EKT120: Computer Programming

3. Passing Array to Function
void initialize (int list [ ]) {
int count;
for (count = 0; count < 5; count ++)
list [count] = 0; }
passing array list [ ] to function
Initialize all element inside array list[ ] to 0
i.e:
list [0]=0; .
list [4]=0
Sem1-06/07
EKT120: Computer Programming

4. Array as Parameters to Function
If size changes (lets say 10 or 20), need to write another function.
Introduce another variable, size without need to write another function.
void initialize (int list [ ], int size) {
int count;
for (count = 0; count < size; count ++)
list [count] = 0; }
Sem1-06/07
EKT120: Computer Programming

5. EKT120: Computer Programming
Constant Arrays
Prevent the function from changing the values in array.
Use word const in declaration.
Function can modify array x but not array y.
void example (int x[ ], const int y[ ], int sizeX[ ],
int sizeY[]) {
….. …. }
Sem1-06/07
EKT120: Computer Programming

6. Initialize all elements inside array x[ ] to 0
Initialize an array to 0
void initializeArray (int x [ ], int sizeX) {
int counter;
for (counter = 0; counter < sizeX; counter ++)
x [counter] = 0; }
Initialize all elements inside array x[ ] to 0
i.e:
x[0]=0,x[1]=0…….x[sizeX-1]
Sem1-06/07
EKT120: Computer Programming

7. Read data and store it in an array
void fillArray (int x [ ], int sizeX) {
int counter;
for (counter = 0; counter < sizeX; counter ++)
scanf (“%d”, &x[counter]); }
Store
Read
Sem1-06/07
EKT120: Computer Programming

8. EKT120: Computer Programming
Print the Array
void printArray (const int x [ ], int sizeX) {
int counter;
for (counter = 0; counter < sizeX; counter ++)
printf (“%d”, x [counter]); }
Sem1-06/07
EKT120: Computer Programming

9. Find & return the sum of an array
int sumArray (const int x [ ], int sizeX) {
int counter;
int sum = 0;
for (counter = 0; counter < sizeX; counter ++)
sum = sum + x [counter];
return sum; }
Constant array int x[ ] with sizeX having element from 0 to (sizeX – 1)
passed to sumArray function.
Sum all elements in array x[ ] with size of sizeX
x[0] + x[1] + ………x[sizeX - 1]
Sem1-06/07
EKT120: Computer Programming

10. Find & return Index of largest element of an array
int indexLargestElement (const int x [ ], int sizeX) {
int counter;
int maxIndex = 0;
for (counter = 0; counter < sizeX; counter ++)
if ( x[maxIndex] < x[counter] )
maxIndex = counter; // copy counter to maxIndex
return maxIndex; }
Program to find the index of the largest element.
Test each element in array x[ ]
x[counter]  test each index starts from 0 to (sizeX – 1)
Sem1-06/07
EKT120: Computer Programming

11. EKT120: Computer Programming
Let sizeX = 3
x[sizeX] = x[3]={2,6,3}
x[0]=2,x[1]=6,x[2]=3
Test each element to find the index of largest element.
x[counter] = x[0]>maxIndex, 2>0
maxIndex=counter maxIndex=0, repeat until counter = 2.
x[counter]=x[1]>2, 6>2
maxIndex=counter maxIndex=1, repeat until counter = 2.
x[counter]=x[2]>6, but 3<6
maxIndex=counter maxIndex=1, counter = 2. exit for loop
return maxIndex=1. x 2 6 3
x[0]
x[1]
x[2]
Sem1-06/07
EKT120: Computer Programming

12. Copy One Array Into Another Array
void copyArray (const int x [ ], int y [ ], int length) {
int counter;
for (counter = 0; counter < length; counter ++)
y [counter] = x [counter]; }
Length = size of array x[ ], array x[ ] is a constant array
y [counter] = x [counter]; // copy each element between arrays
Sem1-06/07
EKT120: Computer Programming

13. How Arrays are passed in a function call
#include <stdio.h>
const int arraySize = 10;
void initializeArray (int x [], int sizeX);
void fillArray (int x [], int sizeX);
void printArray (const int x [], int sizeX);
int sumArray (const int x [], int sizeX);
int indexLargestElement (const int x [], int sizeX);
void copyArray (const int x [], int y [], int length);
Sem1-06/07
EKT120: Computer Programming

14. How Arrays are passed in a function call
int main() {
int listA [arraySize] = {0};
int listB [arraySize];
printArray (listA, arraySize);
initializeArray (listB, arraySize);
printArray (listB, arraySize);
fillArray (listA, arraySize);
sumArray (listA, arraySize);
copyArray (listA, listB, arraySize);
return 0; }
Sem1-06/07
EKT120: Computer Programming

15. EKT120: Computer Programming
Sample Program
#include <stdio.h>
void printArray( const int a[][3]); // function prototype
//function main begins program execution
int main() {
//initialize array1, array2, array3
int array1 [2][3] = { {1, 2, 3}, {4, 5, 6} };
int array2 [2][3] = { 1, 2, 3, 4, 5 };
int array3 [2][3] = { {1, 2 }, { 4 } };
printf (“Values in array1 by row are : \n);
printArray (array1);
printf ("Values in array2 by row are : \n");
printArray (array2);
printf ("Values in array3 by row are : \n");
printArray (array3);
return 0;
} // end of main
Sem1-06/07
EKT120: Computer Programming

16. EKT120: Computer Programming
Sample Program (cont…) Function To Output Array With Two Rows And Three Columns
void printArray (const int a[][3]) {
int i; //row counter
int j; //column counter
//loop through row
for (i = 0; i <= 1; i++)
//output column values
for (j = 0; j <= 2; j++)
printf ("%d ", a[i][j]);
} // end inner for
printf ("\n"); // start new line of output
} // end outer for
} // end function printArray
Sem1-06/07
EKT120: Computer Programming

17. EKT120: Computer Programming
Output
Values in array1 by row are :
1 2 3
4 5 6
Values in array2 by row are :
4 5 0
Values in array3 by row are :
1 2 0
4 0 0
Compare with the following……….
int array1 [2][3] = { {1, 2, 3}, {4, 5, 6} };
int array2 [2][3] = { 1, 2, 3, 4, 5 };
int array3 [2][3] = { {1, 2 }, { 4 } };
Sem1-06/07
EKT120: Computer Programming

18. Details…………review lecture W7 string
Re-Cap from previous lecture…..
Previous….array that contain numerical values in each array element.
String….array that contain a single char in each element including the last element of these arrays is the null character (\0).
String….arrays of characters
Numerical array works element by element
More convenient work with strings by using the address of the first element of string (advantage of pointer).
  pointer becomes very important.
Details…………review lecture W7 string
Sem1-06/07
EKT120: Computer Programming

19. Assigning values to string
The left hand side value of an assignation can only be array items and not the entire array, the probable way to assign a string of characters to an array of char can be shown as:
newstring[0] = ‘W’;
newstring[1] = ‘e’;
newstring[2] = ‘l’;
newstring[3] = ‘c’;
newstring[4] = ‘o’;
newstring[5] = ‘m’;
newstring[6] = ‘e’;
newstring[7] = ‘\0’;
Sem1-06/07
EKT120: Computer Programming

20. Calculation of string size What are the result?
char is 1 byte, the total number of alphabets plus a null would be the size of the string. Example program:
#include <stdio.h>
#include <string.h>
char newstring[] = {'W','e','l','c','o','m','e','\0'};
char mystring[] = "Good Bye";
int main() {
printf ("Size of newstring is %d", sizeof (newstring)); //size of string Welcome
printf ("\nSize of mystring is %d", sizeof (mystring));// size of string Good Bye
return 0; }
Sem1-06/07
EKT120: Computer Programming

21. Character & String manipulation
Eg:
a program may need to verify that an ID number of first year students starts with ’04’.
Determine whether last three characters in a part number are valid.
Built-in functions available – makes it easier.
Sem1-06/07
EKT120: Computer Programming

22. Controlling the Case of a Character
‘K’ is not equal to ‘k’.
Previously use:
if (choice == ‘K’ || choice == ‘k’)
while (choice == ‘K’ || choice == ‘k’)
Can use a function that temporarily converts the letter to uppercase or lowercase before comparing it.
strupr(charVariable)
strlwr(charVariable)
Sem1-06/07
EKT120: Computer Programming

23. Controlling the Case of a Character Example strupr
char repeat;
printf ( “Continue? (Y or N) : “);
scanf (“%c”, &repeat);
while (strupr(repeat) == ‘Y’) {
….. }
While loop performed even though the ‘y’ is entered.
Function strupr temporarily converts the letter to uppercase
Sem1-06/07
EKT120: Computer Programming

24. Controlling the Case of a Character Example of strupr
char name[];
printf (“Enter a name : “);
scanf (“%s”, name);
strupr( name );
printf("The name in uppercase is %s", name );
Function strupr temporarily converts the letter to uppercase even though user keyed lowercase.
Sem1-06/07
EKT120: Computer Programming

25. Sample Program To convert a string to uppercase
#include <stdio.h>
#include <string.h>
void main() {
char name[80]; /* declare an array of characters 0-79 */
printf("Enter in a name in lowercase\n");
scanf( "%s", name );
strupr( name ); // converts to uppercase
printf("The name in uppercase is %s", name ); }
Output
Enter in a name in lowercase
ahmad
The name in uppercase is AHMAD
Sem1-06/07
EKT120: Computer Programming

26. Controlling the Case of a Character
Real value does not changed.
The functions only affect characters of letters or alphabet. Doesn’t affect numbers and special characters such as $ and %.
If the character of already lowercase or uppercase, the function will not affect the real value. It will return the original value.
char repeat = ‘Y’;
letter = strupr(repeat);
Letter = ? affected or not?
Sem1-06/07
EKT120: Computer Programming

27. String Conversion Functions
In <stdlib.h> (general utilities library)
Convert strings of digits to integer and floating-point values
Sem1-06/07
EKT120: Computer Programming

28. Comparison Functions of the String
Comparing strings
Computer compares numeric ASCII codes of characters in string
int strcmp( const char *s1, const char *s2 );
Compares string s1 to s2
Returns a negative number if s1 < s2, zero if s1 == s2 or a positive number if s1 > s2
int strncmp( const char *s1, const char *s2, size_t n );
Compares up to n characters of string s1 to s2
Returns values as above
Sem1-06/07
EKT120: Computer Programming

29. EKT120: Computer Programming
ASCII Table
ASCII Character Set 1 2 3 4 5 6 7 8 9
nul
soh
stx
etx
eot
enq
ack
bel bs ht If vt ff cr so si
dle
dc1
dc2
dc3
dc4
nak
syn
etb
can em
sub
esc fs gs rs us sp ! “ # $ %
& ` ( ) * + , - . / : ;
< =
> ? @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z [ \ ] ^ _ ’ a b 10 d e f g h i j k l 11 n o p q r s t v 12 x y z { | } ~
del
Sem1-06/07
EKT120: Computer Programming

30. EKT120: Computer Programming
Sample program 1
#include <stdio.h>
#include <string.h>
int main() {
char string1[ 20 ], string2[ 20 ]; //declaration of string1 and string2
int result;
printf( "Enter two strings: " );
scanf( "%s%s", string1, string2 );
result = strcmp( string1, string2 ); // compare between string1 and string2
if ( result > 0 )
printf( "\"%s\" is greater than \"%s\"\n", string1, string2 );
else if ( result == 0 )
printf( "\"%s\" is equal to \"%s\"\n", string1, string2 );
else
printf( "\"%s\" is less than \"%s\"\n", string1, string2 );
return 0; }
Sem1-06/07
EKT120: Computer Programming

31. EKT120: Computer Programming
Output
Enter two strings: computer programming
"computer" is less than "programming"
Enter two strings: programming computer
"programming" is greater than "computer"
Sem1-06/07
EKT120: Computer Programming

32. EKT120: Computer Programming
Sample program 2
#include <stdio.h>
#include <string.h>
int main() {
char string1[ 20 ], string2[ 20 ];
int result, compareCount;
printf( "Enter two strings: " );
scanf( "%s%s", string1, string2 );
printf( "How many characters should be compared: " );
scanf( "%d", &compareCount );
result = strncmp( string1, string2, compareCount );
if ( result > 0 )
printf( "\"%s\" is greater than \"%s\" up to %d characters\n",
string1, string2, compareCount );
else if ( result == 0 )
printf( "\"%s\" is equal to \"%s\" up to %d characters\n",
else
printf( "\"%s\" is less than \"%s\" up to %d characters\n",
return 0; }
Sem1-06/07
EKT120: Computer Programming

33. EKT120: Computer Programming
Output
Enter two strings: computer programming
How many characters should be compared: 7
"computer" is less than "programming" up to 7 characters
Enter two strings: programming computer
"programming" is greater than "computer" up to 7 characters
Sem1-06/07
EKT120: Computer Programming

34. Built in Functions for String Handling
strcat Appends a string
strchr Finds first occurrence of a given character
strcmp Compares two strings
strcmpi Compares two strings, non-case sensitive
strcpy Copies one string to another
strlen Finds length of a string
strlwr Converts a string to lowercase
strnca t Appends n characters of string
strncmp Compares n characters of two strings
strncpy Copies n characters of one string to another
strnset Sets n characters of string to a given character
strrchr Finds last occurrence of given character in string
strrev Reverses string
strset Sets all characters of string to a given character
strspn Finds first substring from given character set in string
strupr Converts string to uppercase
Sem1-06/07
EKT120: Computer Programming