Module-3: Arrays, Strings and Functions

Transcription

1 Introduction to Arrays: Module-3: Arrays, Strings and Functions Normally, the programmer makes the use of scalar variable to store and process single value. However, it is necessary for the programmer to store and process large volume of data in computer s memory while developing the programs to solve complex problems and is possible by making the use of data structure or derived data type named array. The examples to store and process large volume of data in computers memory by using an array are as follow. i. To store and process roll numbers of 100 students int rno[100]; ii. To store and process total marks of 100 students int marks[100]; iii. To store and process name of a candidate char name[25]; iv. To store and process names of 100 candidates char name[100][25]; Definition of an array: An array can defined as a collection of related data elements of the same data type stored in computer s memory to store and process large volume of data Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 1 Or An array can defined as a fixed size sequenced collection of data elements of similar data type stored in consecutive computer s memory Examples: 1. To define an array with the name a of type int i.e. to store and process maximum number of 100 integer values instead of defining 100 separate variables. int a[100]; Index/subscript a The machine allocates 100 memories continuously with the common name a. The individual memories can be identified by common array name with the index values i.e. starts with 0 and end with ARRAY SIZE-1. The integer values can be stored in array elements with common array name a with different index values as follow. a[0]= 15, a[1]=25,a[2]=35, a[3]=45,a[5]=55,.,a[99]=125; Index a

2 bytes). The total memory allocated by this array is 200 bytes (100 memories x 2 bytes= To define an array with the name avg of float type to store and process percentage of marks of 100 students instead of defining 100 separate variables. float avg[100]; Index avg The floating point values can be stored in array elements with common array name avg with different index values as follow. bytes). avg[0]= 90.59, avg[1]=80.89,avg[2]=70.88, avg[3]=93.67,avg[5]=87.55,.,avg[99]=69.25; Index a The total memory allocated by this array is 400 bytes (100 memories x 4 bytes= To store and process name of a student in character array or string variable. char name[25]; strcpy(name, John ); /* character array or string variable*/ Index name J o h n \0 The total memory allocated by this array is 25 bytes (25 memories x 1 byte=25 bytes). 4. To store two strings (words) char str1[50], str2[50]; Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 2

3 Types of arrays: The arrays can be classified according to the volume of data to be stored in computer s memory. 1. One dimensional array e.g. int a[100]; 2. Two dimensional array e.g. int a[100][100]; 3. Multi dimensional array e.g. int a[100][100][100]; 1. One dimensional array: One dimensional array can defined as a collection of related data elements of the same data type stored in consecutive computer s memory to store and process linear list of data elements The individual arrays elements can be processed by using common array name with different index that starts with 0 and ends with the ARRAY SIZE 1. Declaration of one-dimensional array: The one dimensional array must be declared in the declaration part of the main() before the array elements are used in the executable part of main() by using following syntax. Syntax: where, data_type array_name[array_size]; data_type the data type of data to be stored and processed in computer s memory like int, float, char, double, long int, etc. array_name valid identifier ARRAY_SIZE the integer constant indicating maximum number of data elements can be stored. Examples: int a[5]; float price[5]; Index a Index price Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 3

4 double result[5]; Index result char name[5]; Index name char city[5]; Index city Note: Computer allocates 5 memory locations with garbage (unknown) values Initialization of one dimensional array: The process of assigning the values to the defined array elements is called initialization of array. The arrays can be initialized with the values in the following two ways. 1. Compile Time Array Initialization 2. Run Time Array Initialization 1. Compile Time Array Initialization: If the values are well known by programmers well in advance, then the programmer makes the use of compile time initialization. The process of assigning the values during the declaration of arrays in the declaration part of main() is called compile time initialization. The syntax is as follow. Syntax: data_type array_name[array_size]=value1,value 2,.,Value n; where, data_type the data type of data to be stored and processed in computer s memory like int, float, char, double, long int, etc. array_name valid identifier ARRAY_SIZE the integer constant indicating maximum number of data elements can be stored. Examples: 1. int a[5]=10,20,30,40,50; Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 4

5 or B.L.D.E.A s Vachana Pitamaha Dr. P. G. Halakatti College of Engineering & Technology, Vijyapur-03. a[0]=10, a[1]=20, a[2]=30, a[3]=40, a[4]=50; Index A float price[5]=55.50,99.50,100.50,75.60,50.60; Index price char name[5]= John ; or char name[5]= J, o, h, n ; or char name[ ]= John Index Name J O H n \0 char name[5]= J ; Index Name J \0 \0 \0 \0 4. int a[5]=0,0,0,0,0; or int a[5]=0; Index a int a[5]=10, 20; Index a int a[3]=1,2,3,4,5; /* invalid i.e. to many initialization*/ 2. Run Time Array Initialization: If the values are not known by programmers in advance then the programmer makes the use of run time initialization. It helps the programmers to read unknown values from the end users of a program by the keyboard by using input functions like scanf() getch() and gets(),etc. Examples: Partial Initialization of Array: If the number of values to be initialized is less than the size of the array then it is called as partial initialization. The remaining locations will be initialized to zero automatically Ex: Consider the array shown below Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 5

6 int p[5]=10,20; Even though we have declared 5 as a array-size but we have initialized only 2 elements in the array. So other locations are initialized to 0 automatically by compiler as shown below. Index p[0] p[1] p[2] p[3] p[5] Here, elements of index 2,3 and 4 are initialized to 0 automatically by compiler Array Initialization without Size: Consider the example shown below int b[ ]=10,15,20,25,30; Size is not specified In this initialization even though we have not specified the size of array b, but array elements are initialized with 5 different values. The array size will be set to total number of values specified in the array. The compiler will calculate the size of array based on the number of initial values. Since number of elements is 5 so totally 5*2bytes = 10 bytes are reserved where 2 is size of integer. Accessing the element of array: Consider an array consist of 7 integer element int p[7]=15,9,8,19,29,36,85; We can access the elements of array using index or subscript of element. Index gives the position of the elements in the array. Index p[0] p[1] p[2] p[3] p[4] p[5] p[6] p[0]=15, p[1]=9, p[2]=8, p[3]=19, p[4]=29, p[5]=36, p[6]=85 Index of first element of array is 0. Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 6

7 1. To read and display 5 integer values from a keyboard by using an array. #include<conio.h> int a[5],i; printf("\n Enter any 5 integer values"); for(i=0;i<5;i++) scanf("%d",&a[i]); for(i=0;i<5;i++) printf("\n%d",a[i]); 2. To read and display n integer values from a keyboard by using an array. #include<conio.h> int a[50],i,n; printf("\n Enter n: "); scanf("%d",&n); printf("\n Enter %d integer values: ",n); for(i=0;i<n;i++) scanf("%d",&a[i]); printf("\n Array Elements "); for(i=0;i<n;i++) printf("\n%d",a[i]); a[0] a[1] a[2] a[3] a[4] Enter any 5 integer values Enter n: 7 Enter 7 integer values Array Elements Assignment Questions: Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 7

8 1. What is one dimensional array? Explain its declaration and initialization with syntax and examples. (2+2+2=6 marks) (Model QP) 2. What is two dimensional array? Explain its declaration and initialization with syntax and examples. (2+2+2=6 marks) 3. Write a c program to implement bubble sort technique. 4. Write a c program to find largest of n numbers. 5. Write a c program to read N integers into an array A and to i. Find the sum of odd numbers ii. Find the sum of even numbers iii. Find the average of all numbers Output the results computed with appropriate headings. (06 marks June/July 2015) 6. Write a program to multiple of two arrays of given order a[m x n] and b[ p x q] (09 marks Jan. 2015) Anyone who stops learning is old, whether at twenty or eighty~ Henry Ford When Henry Ford decided to produce his famous V-8 motor, he chose to build an engine with the entire eight cylinders cast in one block, and instructed his engineers to produce a design for the engine. The design was placed on paper, but the engineers agreed, to a man, that it was simply impossible to cast an eight-cylinder engine-block in one piece. Ford replied,''produce it anyway. ~ Henry Ford What we usually consider as impossible are simply engineering problems ~ Michio Kaku *** Programming Examples on one dimensional arrays /* To find largest and lowest of n numbers*/ #include<conio.h> int a[5],i,n,max,min; printf("\n Enter n: "); scanf("%d",&n); printf("\n Enter %d values: ",n); for(i=0;i<n;i++) scanf("%d",&a[i]); max=min=a[0]; for(i=1;i<n;i++) if (a[i]>max) Enter n: 5 Enter 5 values: Largest number is 67 Lowest number is 2 Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 8

9 max=a[i]; if (a[i]<min) min=a[i]; printf("\n Largest number is %d",max); printf("\n Lowest number is %d",min); Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 9

10 /* To find sum of odd,even,all and avg of N numbers by using array */ #include<conio.h> int a[5],i,n,sum=0,esum=0,osum=0; float avg; printf("\n Enter n: "); scanf("%d",&n); printf("\n Enter %d values: ",n); for(i=0;i<n;i++) scanf("%d",&a[i]); for(i=0;i<n;i++) if (a[i]%2==0) esum=sum+i; else osum=osum+i; sum=sum+a[i]; avg=(float)sum/n; printf("\n Sum of even numbers=%d",esum); printf("\n Sum of odd numbers=%d",osum); printf("\n Sum of all numbers=%d",sum); printf("\n Average of all numbers=%f",avg); Enter n: 5 Enter 5 values: Sum of even numbers = 9 Sum of even numbers = 6 Sum of all numbers = 15 Average of all numbers = Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 10

11 Sorting Techniques in C The process of arranging the elements in the ascending order or descending order is the sorting. There are 2 sorting technique 1) Bubble Sort 2) Selection Sort Bubble Sort: Bubble sort technique starts by comparing the first two elements of an array and swap the elements if necessary (Swapping is nothing but interchanging the elements), i.e., if you want to sort the elements of array in ascending order and if the first element is greater than second then, you need to swap the elements. If the first element is smaller than second, you must not swap the element. Then, again second and third elements are compared and swapped if it is necessary and this process go on until last and second last element is compared and swapped. This completes the first step of bubble sort. In the first level of sorting highest elements of the list will settles at bottom position. In the second level of sorting second highest element will settles at second bottom position and so on. Each and every level largest element settles at the bottom and smallest elements bubbles up. The following figure illustrates the working of bubble sort Bubble sort technique Here, there are 5 elements to the sorted. So, there are 4 steps(levels). Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 11

12 /* Program to sort n numbers using Bubble sort technique */ #include<conio.h> int n, a[25], i, j, temp; printf("enter n:"); scanf("%d",&n); printf("\n Enter any %d values",n); for(i=0;i<n;i++) scanf("%d",&a[i]); printf("\nbefore sorting\n"); for(i=0;i<n;i++) printf("\t%d",a[i]); for(i=0;i<n;i++) for(j=0; j<n-i-1 ;j++) if (a[j]> a[j+1]) temp=a[j]; a[j]=a[j+1]; a[j+1]= temp; printf("\nafter sorting\n"); for(i=0;i<n;i++) printf("\t%d",a[i]); Enter n: 5 Enter any 5 values: Before Sorting After Sorting Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 12

13 Selection Sort: Selection sort algorithm starts by comparing first two elements of an array and swap the elements if necessary, i.e., if you want to sort the elements of array in ascending order and if the first element is greater than second then, you need to swap the elements but, if the first element is smaller than second, leave the elements as it is. Then, again first element and third element are compared and swapped if necessary. This process goes on until first and last element of an array is compared. This completes the first step of selection sort. If there are n elements to be sorted then, the process mentioned above should be repeated n -1times to get required result. Following figure shows the working of selection sort technique Fig: Selection sort technique In above example the first number 20 is compared with second number 12. Since first number is larger than second number then swap the numbers. Then compare the second number with third number if swapping is necessary then swap the number otherwise compare third element with fourth element and so on up to n. C Program for illustrating Selection sort technique Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 13

14 /* C Program to sort the numbers in ascending order using selection sort technique*/ #include<conio.h> void main( ) int n,i,j,temp,a[20]; printf("enter total elements: "); scanf("%d",&n); printf("enter %d elements: ",n); for(i=0;i<n;i++) scanf("%d",&a[i]); for(i=0;i<n;i++) for(j=i+1;j<n;j++) if(a[i]>a[j]) temp=a[i]; a[i]=a[j]; a[j]=temp; printf("after sorting is: "); for(i=0;i<n;i++) printf(" %d",a[i]); getch( ); /*Swapping technique*/ Output Enter total elements:5 Enter 5 elements: After Sorting is: Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 14

15 /* Program to find sum and average of N numbers using array */ #include<conio.h> int a[25],n,i,sum=0; float avg; printf("enter n:"); scanf("%d",&n); printf("\nenter any %d values",n); for(i=0;i<n;i++) scanf("%d",&a[i]); for(i=0;i<n;i++) sum=sum+a[i]; avg=(float)sum/n; printf("\n Sum of all numbers=%d",sum); printf("\n Average of all numbers=%f",avg); Enter n: 5 Enter any 5 values: Sum of all numbers = 15 Average of all numbers = Bell Teacher: A new student approached the Zen master and asked how he should prepare himself for his training. "Think of me a bell," the master explained. "Give me a soft tap, and you will get a tiny ping. Strike hard, and you'll receive a loud, resounding peal." People's reactions to this story: "You get out of something what you put into it." "The more you try, the more a good teacher will help." "Be careful what you ask for. The universe may just provide you with what you seek." "Sounds like the master is saying pay me a lot, and I will help you a lot; pay me little, and that's what I'll give you in return." "I think the teacher was warning the student that if he is struck he will strike back with equal force." Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 15

16 Searching Techniques in C Programming Language More often we will be working on large amount of data. It may be necessary to determine whether a particular item is present in that large amount of data. The Process of finding a particular element in the large amount of data is called as Searching. There are 2 types of searching techniques 1) Linear Search 2) Binary Search 1) Linear Search( Sequential Search): A linear search also called as Sequential Search is a simple searching technique. In this technique we search for a given specific element called as key element in the large list of data in sequential order( One after another) from first element to last element. If the key element is present in the list of data then search is Successful. Otherwise, search is Unsuccessful. Ex: int a[5]=10,20,30,40,50; Index a[0] a[1] a[2] a[3] a[4] Consider above example where array a contains 5 integer elements. If user wants to search a key element 30 from given list of elements, then search begins from first element of array i.e. 10(Index is 0). Then it checks this element with given key element. If both element are same then it is called as SUCESSFUL SEARCH and it returns the position of that particular element in the array. If the element is not present in the array then it is called as UNSUCESSFUL SEARCH and it returns -1. So here in above example the search is successful and the key element is present at Position 3(Position=index+1). Following is the C Program for Linear Search Technique Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 16

17 /* Program to implement linear search technique by using an array*/ #include<conio.h> int a[25],n,i,key ; printf("enter n:"); scanf("%d",&n); printf("\n Enter any %d values",n); for(i=0;i<n;i++) scanf("%d",&a[i]); printf("\n Enter item to be search:"); scanf("%d",&key); for(i=0;i<n;i++) if (key==a[i]) printf("\n Item found at %d position",i+1); exit(); printf("\n Item not found!"); Enter n: 5 Enter any 5 values: Enter item to be search: 88 Item found at 4 position Enter n: 5 Enter any 5 values: Enter item to be search: 100 Item not found! Advantages: 1) Very simple approach. 2) Works well for small arrays 3) Used to search when the elements are not sorted. Disadvantages: 1) Less efficient if the array is large 2) If the elements are the already sorted, linear search is not efficient. Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 17

18 Binary Search Technique: A binary search is simple and very efficient searching technique which can be applied if the items to be compared are either in ascending order or descending order. The general idea behind Binary Search technique is finding middle element from the sorted list of element. If given Key element is less than middle element search towards left side of middle element, otherwise search towards right side. This process is repeated until key element is found or key element is not found. If key element is found then return position of that element. If key element is not found then retuen -1. Consider the array shown below int a[10]=10,20,30,40,50,60,70,80,90,100; index: a[0] a[1] a[2] a[3] a[4] a[5] a[6] a[7] a[8] a[9] low high low --> Represents the first element of array where index is 0. Hence low=0. High --> Represents the last element of array where last index is 9 i.e. n-1. Hence high=n-1. low=0 high=n-1( n is total number of elements) So position of middle element is obtained by mid=(low+high)/2 Here in above example mid=(0+9)/2=4. Because the mid value is integer. This suggest that the element which is at index 4 is the middle element. So middle element is 50. Case 1) Now key element is compared with middle element. If both elements are same then return mid value. if(key==a[mid]) return mid; Case 2) If key element to be search is less than middle element then search towards left of the middle element. i.e. Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 18

19 if(key<a[mid]) high=mid-1; high=mid-1 searches towards left side of middle element Case 3) If Key element to be search is greater than middle element then search towards right side of middle element. i.e. if(key>a[mid]) low=mid+1; low=mid+1 searches towards right side of middle element. Finally if key element to be searched is not present in the list, then it returns -1. /* Program to implement binary search technique by using an array*/ #include<conio.h> int a[25], n, i, key, low, high, mid; float avg; printf("enter n:"); scanf("%d",&n); printf("\n Enter any %d values in ascending order: ",n); for(i=0;i<n;i++) scanf("%d",&a[i]); printf("\n Enter item to be search:"); scanf("%d",&key); low=0; high=n-1; while(low<=high) mid=(low+high)/2; if (key==a[mid]) printf("\n Item found at %d position",mid+1); Enter n: 5 Enter any 5 values in ascending order: Enter item to be search: 3 Item found at 3 position Enter n: 5 Enter any 5 values in ascending order: Enter item to be search: 8 Item not found! Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 19

20 exit(0); if (key>a[mid]) low=mid+1; if (key<a[mid]) high=mid-1; printf("\n Item not found!"); Advantage: Very efficient searching technique. Disadvantage: Array elements should be in sorted. Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 20

21 Two dimensional arrays: A two dimensional array helps the programmers to store and process table of data elements of similar type in computer s primary memory RAM. It is similar to a matrix containing numbers of rows and columns. The rows and columns of 2D array are indexed by starting from 0(zero). i.e row index starts with 0 and end with ROW_SIZE-1 and column index starts with 0 and end with COLUMN_SIZE-1. The 2D arrays elements can be processed by using common array name with two index representing row and column. Examples: 1. To store and process 6 subject marks of 5 students. int a[5][6]; Col-0 Col-1 Col-2 Col-3 Col-4 Col-5 Row Row-1 Row-2 Row-3 Row In each row, programmer can store 6 subject marks of each student. a[0][0]=65, a[0][1]=75, a[0][2]=90, a[0][3]=80, a[0][4]=66, a[0][5]=68;. a[4][0]=50, a[4][1]=60, a[4][2]=70, a[4][3]=80, a[4][4]=90, a[4][5]=99; 2. To store and process table of integer values containing 2 rows & 3 columns. int a[2][3]; To store and process table of floating point numbers of the size 3 x float b[3][2]; 0 1 Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 21

22 Declaration of two-dimensional array: The two dimensional array must be declared in the declaration part of the main() before the array elements are used in the executable part of main() by giving common name with two indexes representing no. of rows and columns. The syntax is as follow. Syntax: where, data_type array_name[row_size] [COLUMN_SIZE]; data_type the data type of data to be stored and processed in computer s memory like int, float, char, double, long int, etc. array_name valid identifier ROW_SIZE & COLUMN_SIZE the maximum number of row and column elements can be stored ( The values should be integer). Examples: 1. To store the integer values for 5 x 5 matrix. int a[5][5]; Col-0 Col-1 Col-2 Col-3 Col-4 Row-0 Row-1 Row-2 Row-3 Row-4 Total memory occupied by this array is ( 5 x 5 x 2 bytes=50 bytes) 2. To store and process table of integer values containing 2 rows & 3 columns. 0 1 int a[2][3]; To store the names of 100 students char name[100][25]; Total memory occupied by this array is ( 100 x 25 x 1 byte=25000 bytes) Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 22

23 Initialization of two dimensional array: The process of assigning the values to the defined array elements of 2D array is called initialization of 2D array. The array elements can be initialized with different in the following two ways. 1. Compile Time Array Initialization 2. Run Time Array Initialization 1. Compile Time Array Initialization: If the values are well known by programmers in advance, then the programmer makes the use of compile time initialization. i.e the process of assigning the values during the declaration of arrays in the declaration part of main() is called compile time initialization. The syntax is as follow. Syntax: Examples: data_type array_name[row_size] [COLUMN_SIZE]= list of values, list of values, list of values ; int a[2][3]= or int a[2][3]=10,20,30,40,50,60; 10,20,30, 40,50,60 ; int a[3][2]=10,20,30,40,50,60; int a[ ][2]=0,0,0,0; Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 23

24 1. Run Time Array Initialization: If the values are not known by programmers in advance then the programmer makes the use of run time initialization. i.e. programmer reads values from users through the keyboard by using input functions like scanf() getch() and gets(),etc. Examples: 1. To read and display integer values for m x n matrix by using 2D array. /* To read and display values for (m x n) matrix*/ #include<conio.h> int a[25][25],m,n,i,j; printf("enter the order of matrix A:"); scanf("%d%d",&m,&n); printf("\n Enter %d values in row order: ",m*n); for(i=0;i<m;i++) for(j=0;j<n;j++) scanf("%d",&a[i][j]); Enter the order of matrix A: 2 3 Enter 6 values in row order: printf("\n Array Elements \n"); Array Elements for(i=0;i<m;i++) for(j=0;j<n;j++) printf("\t%d",a[i][j]); printf("\n"); Assignments: 1. Write a c program to find addition of two matrices A and B of the same size. 2. Write a c program to find multiplication two matrices A(m,n) and B(p,q). Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 24

25 /* Addition of two matrices*/ #include<conio.h> int a[25][25],b[25][25],c[25][25],m,n,i,j; printf("enter the order of both the matrix A and B:"); scanf("%d%d",&m,&n); printf("\nenter %d values of A matrix: ",m*n); for(i=0;i<m;i++) for(j=0;j<n;j++) scanf("%d",&a[i][j]); printf("\nenter %d values of B matrix: ",m*n); for(i=0;i<m;i++) for(j=0;j<n;j++) scanf("%d",&b[i][j]); /* code to find addition of matrix*/ for(i=0;i<m;i++) for(j=0;j<n;j++) c[i][j]=a[i][j]+b[i][j]; printf("\n Resultant Matrix \n"); for(i=0;i<m;i++) for(j=0;j<n;j++) printf("\t%d",c[i][j]); printf("\n"); Enter the order of both matrix A & B : 2 3 Enter 6 values of A matrix : Enter 6 values of B matrix : Resultant Matrix Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 25

26 /* Substraction of two matrices*/ #include<conio.h> int a[25][25],b[25][25],c[25][25],m,n,i,j; printf("enter the order of both the matrix A and B:"); scanf("%d%d",&m,&n); printf("\nenter %d values of A matrix: ",m*n); for(i=0;i<m;i++) for(j=0;j<n;j++) scanf("%d",&a[i][j]); printf("\nenter %d values of B matrix: ",m*n); for(i=0;i<m;i++) for(j=0;j<n;j++) scanf("%d",&b[i][j]); /* code to find substraction of matrix*/ for(i=0;i<m;i++) for(j=0;j<n;j++) c[i][j]=a[i][j]-b[i][j]; printf("\n Resultant Matrix \n"); for(i=0;i<m;i++) for(j=0;j<n;j++) printf("\t%d",c[i][j]); printf("\n"); Enter the order of both matrix A & B : 2 3 Enter 6 values of A matrix : Enter 6 values of B matrix : Resultant Matrix Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 26

27 /* Multiplication of two matrices*/ #include<conio.h> int a[25][25],b[25][25],c[25][25],m,n,p,q,i,j,k; printf("enter the order of matrix A:"); scanf("%d%d",&m,&n); printf("enter the order of matrix B:"); scanf("%d%d",&p,&q); if (n==p) printf("\n Multiplication of A and B is possible\n"); printf("\nenter values of A matrix: "); for(i=0;i<m;i++) for(j=0;j<n;j++) scanf("%d",&a[i][j]); printf("\nenter values of B matrix: "); for(i=0;i<p;i++) for(j=0;j<q;j++) scanf("%d",&b[i][j]); /* code to find multiplication of matrix*/ for(i=0;i<m;i++) for(j=0;j<n;j++) c[i][j]=0; for(k=0;k<n;k++) c[i][j]+=a[i][k]*b[k][j]; printf("\n Resultant Matrix \n"); for(i=0;i<m;i++) for(j=0;j<q;j++) printf("\t%d",c[i][j]); printf("\n"); else printf("\n Multiplication is not possible!"); Enter the order matrix A & B : 2 3 Enter the order matrix A & B : 3 2 Multiplication is possible Enter values of A matrix : Enter values of B matrix : Resultant Matrix Enter the order matrix A & B : 2 3 Enter the order matrix A & B : 2 3 Multiplication is not possible Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 27

28 /* C Program to print transpose of given matrix*/ #include <stdio.h> #include<conio.h> int a[10][10]; int i, j, m, n; printf("enter the order of the matrix \n"); scanf("%d %d", &m, &n); printf("enter the coefiicients of the matrix\n"); for (i = 0; i < m; ++i) for (j = 0; j < n; ++j) scanf("%d", &a[i][j]); Output: Enter the order of the matrix printf("the given matrix is \n"); 3 3 for (i = 0; i < m; ++i) Enter the coefiicients of the for (j = 0; j < n; ++j) matrix printf(" %d", a[i][j]); printf("\n"); The given matrix is printf("transpose of matrix is \n"); for (j = 0; j < n; ++j) for (i = 0; i < m; ++i) Transpose of matrix is printf(" %d", a[i][j]); printf("\n"); Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 28

29 /* C Program to print principal diagonal elements of the matrix*/ #include<conio.h> int a[20][20],i,j,m,n; printf("enter the rows and columns of the matrixs\n"); scanf("%d%d",&m,&n); printf("enter the first matrics\n"); for(i=0;i<m;i++) for(j=0;j<n;j++) scanf("%d",&a[i][j]); //reads the matrics printf("the diagonal element of the matrics are\n"); for(i=0;i<m;i++) for(j=0;j<n;j++) if(i==j) printf("%d,",a[i][j]); //prints the diagonal element of the matrics Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 29

30 Introduction to Strings The use of strings plays very important role, while developing the user friendly software. Hence, it is necessary for the programmer to store and process strings within computers memory. To read and display the strings, the programmer makes the use of I/O functions like scanf(), printf(), gets() and puts(). C supports different string handling functions like strcmp(), strcat(), strcpy() and strupr(),strlwr(), etc. to perform different operations on strings to get desired results. A string constant or literal can be defined as a sequence of characters enclosed in double quotes that will be treated as single data element Technically, a string constant is an array of characters. By default, each string ends with the NULL character (\0) that helps the programmer to identify the end of string. Examples: 1) Brain W. Kernighan and Dennis M. Ritchie 2) Computer Programming in C 3) VTU V T U \0 4) A 5) 2015 and 6) etc. Declaration and Initialization of string variables: The character arrays are also called as string variables. The string variables must be defined and initialized in same way of array declaration and initialization. Syntax: char string_variable[size]; Example: 1) To store name of a student. char name[25]; strcpy(name, Thomas ); Name T h o m a s \0 \0 Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 30

31 2) To store names of 3 students. char name[5][25]; strcpy(name[0], Thomas ); strcpy(name[1], Alice ); strcpy(name[2], Bob ); T h o m a s \0 \0 1 A l i c e \0 \0 2 B o b \0 \0 Reading and Writing Strings: The strings can be read and write by using following I/O functions. 1. scanf() and printf() 2. gets() and puts() The scanf( ) reads a string until white space found from a keyboard, whereas gets( ) reads a string until user press ENTER KEY. The printf( ) helps to write (display) strings on the monitor screen in different formats with appropriate message, whereas puts () helps to display only the string on monitor screen without format. /* To read and siplay strings by using scanf() and printf() */ char name[5][25]; printf("enter your name: "); scanf("%s",name); printf("hello! %s",name); /* To read and siplay strings by using gets() and puts() */ char name[25]; printf("enter your name"); gets(name); printf("hello! "); puts(name); Enter your name: Alice Bob Hello! Alice Bob Enter your name: Alice Bob Hello! Alice Bob Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 31

32 /* Program to find length of a string without using string built-in function*/ #include<conio.h> char str[25]; int i,count=0; printf("enter a string"); gets(str); for(i=0;str[i]!='\0';i++) count++; printf("\n Length of a string is %d",count); Enter a string: Alice Length of a string is 5 /* Program to copy one string1 into string2 without using string built-in function*/ #include<conio.h> char str1[25],str2[25]; int i; printf("enter string1 to be copy: "); gets(str1); for(i=0;str1[i]!='\0';i++) str2[i]=str1[i]; str2[i]='\0'; printf("\nstring Copied\n"); printf("\nstring1=%s String2=%s",str1,str2); Enter string1 to be copy: Alice String Copied String1= Alice String2=Alice /* To reverse a string without using string builtin function*/ #include<string.h> char str[25]; int i,len,temp; printf("enter string to be reverse: "); gets(str); len=strlen(str)-1; for(i=0;i<strlen(str)/2;i++) temp=str[i]; str[i]=str[len]; str[len--]=temp; printf("\n The reversed string is %s",str); Enter string to be reverse: tech The reversed string is hcet Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 32

33 String Manipulating Functions/ String Built-in Function: C supports different string handling functions to perform different operations on strings. All the string handling functions are stored in string.h file. Some of the most common used string functions are as follow. Sl.No. Function Description 1 strlen() Returns number of characters in the given string 2 strcpy() Copies the given source string to another destination string variable 3 strncpy() Copies first n characters from source to destination 4 strcmp() Compares two strings for their similarity 5 strncmp() Compares first n characters from two strings for their similarity 6 strcat() Concatenates (joins) two strings into single string 7 strncat() Concatenates first n characters from source string to destination 8 strupr() Converts characters into uppercase 9 strlwr() Converts characters into lowercase 10 strrev() Reverses a given string 1. strlen(): It returns the number of characters in the given string. Syntax: strlen(string); Examples: Programming Example: int len; len=strlen( vtu ); len=3 /* To find length of a string */ #include<string.h> char str[50]; int len; printf("enter a string"); gets(str); len=strlen(str); int len; char str[]= vtu ; len=strlen(str); len=3 printf("\n Length of the string is %d",len); Enter a string : vtu Length of the string is 3 Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 33

34 2. strcpy(): It copies the contents of source string to another destination string variable. Syntax: strcpy(destination, source string); Examples: char str1[25]= vtu,str2[25]; strcpy(str2,str1); printf( copied string is %s,str2); Programming Example: Copied string is vtu /* To copy a string */ #include<string.h> char str1[50],str2[50]; Enter string1 to be copy : vtu Copied string is vtu printf("enter string1 to be copy: "); gets(str1); strcpy(str2,str1); printf("\n Copied string is %s",str2); 3. strncpy(): It copies the number of characters from source string to another destination string variable. Syntax: strcpy(destination, source string, n); where, n number of characters to be copy Examples: char str1[25]= Technology,str2[25]; strcpy(str2,str1,4); printf( copied string is %s,str2); Copied string is Tech 4. strcmp(): It compares given two strings for their similarity character by character. If, the given strings are same then it returns zero; otherwise, non-zero (ASCII difference of dissimilar characters). Syntax: strcmp(string1,string2); Examples: char str1[25]= VTU,str2[25]= VTU ; int temp; temp=strcmp(str1,str2); temp=0 /* because both are same */ Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 34

35 char str1[25]= Ant,str2[25]= Cat ; int temp; temp=strcmp(str1,str2); temp=-2 /* ASCII of A ASCII of C i.e =-2 */ 5. strncmp(): It compares given two strings for their similarity for the specified number of characters from the beginning. If, the given strings are same then it returns zero; otherwise, non-zero (ASCII difference of dissimilar characters). Syntax: strncmp(string1,string2,n); where, n number of characters to be compare. Examples: char str1[25]= THERE,str2[25]= THEIR ; int temp; temp=strncmp(str1,str2,3); temp=0 /* because first 3 characters are same */ 6. strcat(): It concatenates (joins) two strings into a single string. Syntax: strcat(string1,string2); Example: char str1[25]= Honey, str2[25]= well, str3[25]; strcpy(str3,strcat(str1,str2)); printf( %s,str3); Honeywell 7. strncat(): It concatenates (joins) only specified number of characters from source to destination string. Syntax: strncat(string1,string2,n); where, n number of characters to be joined. Example: char str1[25]= Honey, str2[25]= well, str3[25]; strcpy(str3,strcat(str1,str2,2)); printf( %s,str3); Honeywe 8. strrev(): It reverses a string. Syntax: strrev(string); Example: char str1[25]= computer ; strrev(str1); printf( %s,str1); retupmoc Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 35

36 /* check string for palindrome */ #include<string.h> char str1[25],str2[25]; printf("enter a string:"); gets(str1); strcpy(str2,str1); strrev(str1); if(strcmp(str1,str2)==0) printf("\n Palindrome"); else printf("\n Not palindrome"); Enter a string : madam Palindrome Enter a string : teacher Not Palindrome 9. strupr(): It converts the characters of a given string into uppercase. Syntax: strupr(string); Example: char str1[25]= computer ; strupr(str1); printf( %s,str1); COMPUTER 10. strlwr(): It converts the characters of a given string into lowercase. Syntax: strlwr(string); Example: char str1[25]= COMPUTER ; strlwr(str1); printf( %s,str1); computer *** Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 36

37 Functions or Subprograms Introduction to Functions: As we know, every C program permits the programmer to make use only one main ( ) to solve a problem. Hence, it is very difficult for the programmer to solve a large and complex problem by using single main() with only built-in functions. Hence, programmers write different sub programs to do specific task. These subprograms written by programmers are called subprograms or user defined functions or modules. The programming approach in which the given large and complex problem will be divided into many subprograms and are called by main() to do specific task is called modular programming approach. A function can be defined as a subprogram that contains a group of statements to do specific task Examples: int sum (int x, int y) return(x+y); float area (float x) return(3.142*x*x); A function to find sum of two numbers int sum (int x, int y) or int ans; ans=x+y; return (ans); A function to find area of circle or float area (float x) float ans; ans=3.142*x*x; return(ans); A function to find largest of two numbers int large (int x, int y) if (x>y) return x; or int large (int x, int y) int ans; if (x>y) else return y; ans=x; else ans=y; return (ans); Advantages of writing user defined functions 1. Reduction in the size of main( ). 2. Reusability of the written functions. 3. Program maintenance, testing and debugging is easier. 4. Functions can be shared among many C files. 5. Programmers can create their own functions library like header files. 6. Modular programming approach. Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 37

38 Elements of user defined functions: In order to design and develop user defined functions of sub programs the programmer needs to establish and use the following three elements of user defined functions. i. Function declaration or prototype ii. iii. Function call Function definition The programming example that includes all the three elements is as follows. /* to find sum of two numbers by using function*/ int sum(int x, int y); /* function prototype*/ int n1,n2,ans; printf("\n Enter any two numbers"); scanf("%d%d",&n1,&n2); ans=sum(n1,n2); printf("\n Addition is %d",ans); int sum(int x, int y) return (x+y); /* function call*/ /* function definition*/ Enter any two numbers: 7 3 Addition is 10 (i) Function declaration or prototype: The function must be declared in the global declaration part of the C program i.e. before the main( ). It provide three details of function to be write to C-compiler. The syntax is as follows. Syntax: return_type function_name (arguments list); where, return_type The data type of return value like int,cfloat, char, double etc. The default return type is int. function name valid identifier. arguments list Number of inputs or parameters or arguments. Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 38

39 Examples: int sum (int x, int y); or int sum(int, int) /* to find sum*/ float area (float x); or float area (float) /* to find area of circle*/ void STRCOPY(char str1[],char str2[]); /* to copy str1 into str2*/ long int fact(long int x); /* to find factorial */ int isprime (int x); /* to check of prime number*/ Note: If you write the function before the main() then no need to declare the function. ii. Function call: The user defined function is called by the main() function to do specific task by passing the number of actual parameters. Examples: i) ans1=square(n); ans2=cube(n); 2) r=isprime(i); 3) rightrot(x,n); /* function call*/ /* function call*/ /* function call*/ /* function call*/ iv. Function definition: This is the subprogram, which can be written before or after the main(). To write function, the programmer needs to provide three details of function to C compiler. They are, return type, function name and number of parameters to be received. Syntax: return_type function_name (arguments list) local definitions; statements; return (value); Examples: 1) To find addition of factorial of n number. Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 39

40 int sum (int x, int y) int ans; ans=x+y; return (ans); 2) To find factorial of n number. long int fact(int x) int i, prod=1; for(i=1;i<=x;i++) prod=prod*i; return (prod); 3) To check for prime number. int isprime(int x) int i; for(i=2;i<=x/2;i++) if (x%i==0) return 0; return(1); Programming Examples on user defined functions or subprograms /* to find square and cube of number by using functions*/ int square(int); int cube(int); /* function declaration*/ int n,ans1,ans2; printf("\n Enter a number"); scanf("%d",&n); ans1=square(n); /* function call*/ ans2=cube(n); /* function call*/ printf("\n Square is %d",ans1); printf("\n Cube is %d",ans2); Enter a number: 2 Square is 4 Cube is 8 int square(int x) return (x*x); int cube(int x) return (x*x*x); /* function definition*/ /* function definition*/ Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 40

41 /* to find factorial n by using function*/ long int fact(long int x); /* function declaration*/ long int n,ans; printf("\n Enter a number"); scanf("%ld",&n); ans=fact(n); /* function call*/ printf("\n Factorial is %ld",ans); Enter a number: 4 Factorial is 24 long int fact(long int x) long int prod=1; int i; for (i=1;i<=x;i++) prod=prod*i; return(prod); /* function definition*/ /* to check for prime number by using function*/ int isprime(int x); /* function declaration*/ int n,r; printf("\n Enter a number"); scanf("%d",&n); r=isprime(n); /* function call*/ if(r==1) printf("\n %d is prime number",n); else printf("\n %d is not prime number",n); int isprime(int x) /* function definition*/ int i; for (i=2;i<=x/2;i++) if(x%i==0) return 0; return(1); Enter a number: is prime number Enter a number:24 24 is not prime number Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 41

42 /* to copy string1 into string2 by using user defined function*/ void STRCOPY(char str1[],char str2[]); /* function declaration*/ char str1[50],str2[50]; printf("\n Enter string1 to be copy: "); gets(str1); STRCOPY(str1,str2); /* function call*/ void STRCOPY(char str1[],char str2[]) int i; for (i=0;str1[i]!='\0';i++) str2[i]=str1[i]; str2[i]='\0'; printf("\n String copied..."); printf("\n string1=%s string2=%s",str1,str2); /* function definition*/ Enter a string1 to be copy : Happy String copied String1= Happy String2=Happy Assignments 1. Explain string declaration and initialization with examples. 2. Write a c program to find length of a string without using string handling function. 3. Explain any FIVE string manipulating functions with syntax and examples. 4. What is user defined function? Give example. 5. List advantages of writing subprograms or user defined functions? 6. Explain THREE elements of user defined functions with programming example. 7. Write c program to find factorial of n using user defined function. 8. Write user defined function named isprime(n) that returns 1 if the number is prime; otherwise Write user defined function STRCOPY() to copy string1 into string Solve questions from model and annual question papers. Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 42

43 Parameters (Arguments or Inputs) : The inputs given to the functions to do specific task are called parameters or arguments. The parameters are passed by main() to user defined function to process and to get desired result as an output from it. These parameters are classified into following two types. i) Formal parameters ii) Actual parameters Formal Parameters: The parameters used in the function header of function definition are called formal parameters. These parameters receive input data for processing from the actual parameters from the calling function main(). i,e. formal parameters receive data from actual parameters. The changes made to formal parameters do not affect the contents of actual parameters. Examples: int square(int x); /* Here, x is formal or dummy parameter */ int n,ans; printf( Enter a number: ); ans=square(n); /* Here, n is actual parameter*/ printf( \n square is %s,ans); int square(int x) /* Here, x is formal parameter */ return (x*x); Actual Parameters: The parameters used during the function call in the main() function are called actual parameters. These are actual (original) input data received from users of program and passed to user define function to do specific task. i.e. the contents of actual parameters will be copied into formal parameters. Examples: /* Example for actual parameters */ void test(int x,int y); int x=7,y=3; printf("\n Before calling function: Actual parameters "); printf("\n x=%d y=%d", x,y); test(x,y); /* Here, x & y are actual parameters*/ printf("\n After calling function: Actual parameters "); printf("\n x=%d y=%d", x,y); Before calling function: Actual parameters x = 7 y = 3 Inside function: Formal parameters x = 8 y = 4 After calling function: Actual parameters x = 7 y = 3 void test(int x,int y) /* Here, x & y are formal parameters*/ x++; y++; printf("\n Inside function: Formal parameters"); printf("\n x=%d y=%d",x,y); Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 43

44 Categories of Functions based on number of arguments and return value: The functions can be categorized into following 4 types based on the number of parameters or inputs they receive to do specific task and return value. i. Functions with no arguments and no return value ii. Functions with arguments and no return value iii. Functions with arguments and return value iv. Functions with no arguments and return value i. Functions with no arguments and no return value: These functions do not receive any inputs from the calling function main() and do not return any value back to it. But, these functions do specific task. i.e. there is no data transmission between calling and called function. void line(void); line(); line(); printf("\nvtu,belagavi.\n"); line(); line(); void line(void) int i; for(i=1;i<=80;i++) printf("_"); void sum(void); sum(); void sum(void) int n1,n2,ans; printf("\nenter two numbers:"); scanf("%d%d",&n1,&n2); ans=n1+n2; printf("\naddition is %d",ans); VTU,Belagavi Enter any two numbers: 7 3 Addition is 10 Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 44

45 ii. Functions with arguments and no return value: These functions receive inputs from the calling function main() to do specific task; but, do not return any value back to it. The processed data will be displayed by it. Example: void sum(int x,int y); int n1,n2; printf("\nenter two numbers:"); scanf("%d%d",&n1,&n2); sum(n1,n2); void sum(int x,int y) int ans; ans=x+y; printf("\naddition is %d",ans); iii. Functions with arguments and return value: These functions receive inputs from the calling function main() to process and return a value back to it. i.e. data transmission takes place between calling and called function. Example: int sum(int x, int y); int n1,n2,ans; printf("\n Enter any two numbers"); scanf("%d%d",&n1,&n2); ans=sum(n1,n2); printf("\n Addition is %d",ans); int sum(int x, int y) return (x+y); Enter any two numbers: 7 3 Addition is 10 Enter any two numbers: 7 3 Addition is 10 Department of Computer Science and Engineering Class Notes By Miss Laxmi S Shabadi Page 45