05_ArraysAndStrings

UNIT 5

Arrays and Strings

CpE311N: C Programming

Importance of arrays in computer programming.

Array declaration and definition

One-dimensional Array

Two-dimensional Array

Multi-dimensional Array

Strings

Topics


To learn the importance of arrays in computer programming.

To apply concepts of arrays using the C language.

To create simple programs in one, two or multidimensional arrays.

To make simple string programs using the standard string functions.

Objectives


An array is a collection of variables of the same type and placed in memory contiguously .

The set of data of data in an array is only given one name and the indices are used to differentiate each of the data.

The array is important to avoid redundancy of variable declaration and for easy access of data that are placed contiguously in memory.

It is the job of the programmer to ensure that the array is large enough to hold what the program will put in them.

Arrays


Syntax Declaration:<data_type> array_name[size_of_array] = {optional initialization

data};

Example: int num[5]={ 2, 4, 3, 10, 20};

One-Dimensional Array

202 4 3 10

Index 0 1 2 3 4

Data num[0] num[1] num[2] …

Address &num[0] &num[1] &num[2] …

or num

Note: Min Index =0

Max Index = size -1

Important:

The name of the array is the starting address of the array.



Sample Program : Compute Sum of Array Inputs

1 /* Filename: SumArray.c

Program Description: Ask 5 integers and compute the sum.

Programmer: Pedro de la Cruz

Date Written: May 29,2005

*/ Sample Output:

Enter a number: 3

Enter a number: 1

Enter a number: 2

Enter a number: 5

Enter a number: 2

Sum = 13

2

3

4

5

6

7

8

9

10

#include<stdio.h>

int main(void)

{ int num[5];

int x, sum=0;

for(x=0; x,5; x++)

{ printf(“Enter a number: “);

scanf(“%d”, &num[0]);

}

for(x=0; x<5; x++)

sum += num[x];

printf(“\nSum=%d”, sum);

}

11

12

13

14

15

16


Seatwork

Make a program that will ask 10 integers and determine how many numbers are positive, negative or zero.

Make a program that will ask 10 integers and determine how many of the inputs are odd or even numbers.



In C, a string is a group of characters terminated by a null character (‘\0’).

It is necessary to declare character arrays to be one character longer than the size of the string.

Example: char str[6]= “hello”;

Strings

h ‘\0’e l l o


Sample Program : Ask Characters and Make it a String

1 /* Filename: Function1.c Program Description: Ask 4 characters, then make it a string. Programmer: Pedro de la Cruz Date Written: May 29,2005*/

Sample Output:

Enter a character: aEnter a character: bEnter a character: cEnter a character: dString: abcd

23456789

10

#include<stdio.h>int main(void){ char str[5], ch; int x;

for(x=0; x<5; x++) { printf(“\nEnter a character:”); ch=getche( ); str[x]=ch; }

str[x]= ‘\0’;

printf(“\nString: %s”, str);}

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Strings


Sample Program : Ask A String Using A Standard Function

1 /* Filename: Function1.c Program Description: Ask a string using scanf or gets. Programmer: Pedro de la Cruz Date Written: May 29,2005*/

Sample Output:

Enter your name: MayAnnEnter your surname: CruzCruz

23456789

10

#include<stdio.h>int main(void){ char str[80];

printf(“\nEnter your name: “); scanf(“%s”, &str[0]);

printf(“Enter your surname:”); gets(str);

puts(str);

}

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Strings


strcpy( dest, source) –copy the content of source string to dest string

strncpy(dest, source, n) – copy at most n character from source to dest

Common String Library Functions

Sample Program : String Copy

1 /* Filename: StringCopy.c Program Description: Example of strcpy and strncpy. Programmer: Pedro de la Cruz Date Written: May 29,2005*/

Output:

I will passI willhello

2345678

#include<stdio.h>#include<string.h>int main(void){ char s1[80], s2[80]; char s3[6]=“hello”;

strcpy(s1, “I will pass”);strcpy(s2,s3);strncpy(s2,s1,6);

puts(s1);puts(s2);puts(s3);}

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strcat( dest, source) –appends source string to destination string

strncat(dest, source, n) – appends at most n characters of source string to dest


Sample Program : String Concatenate

1 /* Filename: StringConcat.c Program Description: Example of strcat and strncat Programmer: Pedro de la Cruz Date Written: May 29,2005*/

Output:

hello friendhello

2345678

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

int main(void){ char s1[20], s2[20];

strcpy(s1,”hello”);strcpy(s2,” friend”);strcat(s1,s2);strncat(s2,s1,5)

puts(s1);puts(s2);}

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strlen( string) – determines the length of the string excluding the null terminator


Sample Program : String Length

1 /* Filename: StringLength.c Program Description: Example of strlen Programmer: Pedro de la Cruz Date Written: May 29,2005*/

Sample Output:

Enter a string: pasarLength of String: 52

345678


int main(void){ char str[20]; int len;

printf(“Enter a string: “);gets(str);len=strlen(str);

printf(“Length of String: %d”, len);

}

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strcmp( s1, s2) – compares two strings


Return Values:0 s1==s2 <0 s1<s2 >0 s1>s2

Sample Program : String Compare

1 /* Filename: StringLength.c Program Description: Example of strcmp Programmer: Pedro de la Cruz Date Written: May 29,2005*/

Sample Output:

0

2345678


int main(void){ char s1[5]=“hello”; char s2[5]=“hello”; int result;

result = strcmp(s1,s2);printf(“%d”, result);

}

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Seatwork

Ask a string and print it backwards.

Ask 5 strings and display the longest string.

Ask 3 strings and arrange them in alphabetical order.



Syntax Declaration:

<data_type> array_name[row][column] = {optional initialization data};

Example: int num[3][4] = { 1, 2, 3, 4,

5, 6, 7, 8,

9, 3, 1, 0};

Two-Dimensional Array

Note:

Min Col & Row =0

Max Row = Row – 1

Max Col = Column – 1

Size of array = col x row x size of data

Important:

When the name of the array is used with only 1 index specifying the row, it refers to the address of the first element of the row.

1 2 3 4

Column

0 1 2 3

5 6 7 8

9 3 1 0

0

1

2

Row

Data = num[0][0]

Address = &num[0][0]

or num[0]


Two-Dimensional ArraySample Program : Fill a Two-dimensional Array

1 /* Filename: Function1.c Program Description: Ask 6 integers and place it in a 2x3 array. Programmer: Pedro de la Cruz Date Written: May 29,2005*/

Sample Output:

Enter a number: 1Enter a number: 10Enter a number: 2Enter a number: 20Enter a number: 3Enter a number: 30

23456789

10

#include<stdio.h>int main(void){ int x[2][3]; int row, col;

for(row=0; row<3; row++){ for(col=0; col<2; col++) { printf(“Enter a number: “); scanf(“%d”, &num[row][col]); } }

}

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Sample Program : Array of Strings

1 /* Filename: StrArray.c Program Description: Array of Strings Programmer: Pedro de la Cruz Date Written: May 29,2005*/

Sample Output:

Enter a string: IEnter a string: loveEnter a string: programmingIloveprogramming

23456789

10

#include<stdio.h>int main(void){ char s[3][20]; int x;

for(x=0; x<3; x++){ printf(“Enter a string: “); gets(s[x]);}

for(x=0; x<3; x++) puts(s[x]);}

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Two-Dimensional Array


Multidimensional arrays can have three, four or more dimensions.

Example: 3-Dimensional Array

Multidimensional Array

4 5 6 7

3 4 5 6

1 2 3 4

5 6 7 8

0 1 2 30

1

23

4

0 1 2 30

12

Row

Column

Plane

Syntax:

<data_type> array_name[plane][row][column]

int table[3][5][4] =

{ { /*Plane 0*/

{0,1,2,3}, /*Row 0*/

{1,2,3,4}, /*Row 1*/

{3,4,5,6}, /*Row 2*/

{4,5,6,7}, /*Row 3*/

{5,6,7,8}, /*Row 4*/

}

}


Sample Program : Multidimensional Array

1 /* Filename: MultiDim.c Program Description: Multidimensional Array sample Programmer: Pedro de la Cruz Date Written: May 29,2005*/

Output:

0 1 2 31 2 3 42 3 4 5

23456789

10

#include<stdio.h>

main(){ int table[3][3][4]= { { /*Plane 0*/ {0,1,2,3}, {1,2,3,4}, {2,3,4,5}, } };

int plane, row, col;

for(plane=0;plane<1; plane++){ for(row=0; row<3; row++) { for(col=0; col<4; col++) printf(“\t%d”, table[plane][row][col}; printf(“\n”); }}}

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Multidimensional Array


Computer Science: A Structure Programming Approach in C Behrouz A. Fourozan and Richard F. Gilberg

Using Turbo C

Borland Osborne

The C Programming Language

Kernighan and Ritchie

Applications Programming in C

Johnsonbaugh, et.al.

C Programming: The Accessible Guide to Professional Programming Steven Holzner

Problem Solving and Program Design in C Jeri Hanly, et.al

References

05_ArraysAndStrings

Documents

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