Functions and Arrays in C Programming

functions in C

The function in C language is also known as procedure or subroutine in other programming languages.

To perform any task, we can create function. A function can be called many times. It provides modularity and code reusability.

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Advantage of functions in C

There are many advantages of functions.

1) Code Reusability

By creating functions in C, you can call it many times. So we don't need to write the same code again and again.

2) Code optimization

It makes the code optimized, we don't need to write much code.

Suppose, you have to check 3 numbers (781, 883 and 531) whether it is prime number or not. Without using function, you need to write the prime number logic 3 times. So, there is repetition of code.

But if you use functions, you need to write the logic only once and you can reuse it several times.

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Syntax to declare function in C

The syntax of creating function in c language is given below:

1. return_type function_name(data_type parameter...){  
2. //code to be executed  
3. }  

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Syntax to call function in C

The syntax of calling function in c language is given below:

1. variable=function_name(arguments...);  

1) variable: The variable is not mandatory. If function return type is void, you must not provide the variable because void functions doesn't return any value.

2) function_name: The function_name is name of the function to be called.

3) arguments: You need to provide same number of arguments as defined in the function at the time of declaration or definition.

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Example of function in C

Let's see the simple program of function in c language.

1. #include <stdio.h>      
2. #include <conio.h>    
3. //defining function    
4. int cube(int n){  
5. return n*n*n;  
6. }  
7. void main(){      
8. int result1=0,result2=0;    
9. clrscr();      
10.   
11. result1=cube(2);//calling function  
12. result2=cube(3);    
13.       
14. printf("%d \n",result1);  
15. printf("%d \n",result2);  
16.   
17. getch();      
18. }      

Output

8
27

Call by value and call by reference in C

There are two ways to pass value or data to function in C language: call by value and call by reference. Original value is not modified in call by value but it is modified in call by reference.

Let's understand call by value and call by reference in c language one by one.

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Call by value in C

In call by value, original value is not modified.

In call by value, value being passed to the function is locally stored by the function parameter in stack memory location. If you change the value of function parameter, it is changed for the current function only. It will not change the value of variable inside the caller method such as main().

Let's try to understand the concept of call by value in c language by the example given below:

1. #include <stdio.h>  
2. #include <conio.h>  
3. void change(int num) {  
4.     printf("Before adding value inside function num=%d \n",num);  
5.     num=num+100;  
6.     printf("After adding value inside function num=%d \n", num);  
7. }  
8.   
9. int main() {  
10.     int x=100;  
11.     clrscr();  
12.   
13.     printf("Before function call x=%d \n", x);  
14.     change(x);//passing value in function  
15.     printf("After function call x=%d \n", x);  
16.   
17.     getch();  
18.     return 0;  
19. }  

Output

Before function call x=100
Before adding value inside function num=100
After adding value inside function num=200
After function call x=100

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Call by reference in C

In call by reference, original value is modified because we pass reference (address).

Here, address of the value is passed in the function, so actual and formal arguments shares the same address space. Hence, value changed inside the function, is reflected inside as well as outside the function.

Note: To understand the call by reference, you must have the basic knowledge of pointers.

Let's try to understand the concept of call by reference in c language by the example given below:

1. #include <stdio.h>  
2. #include <conio.h>  
3. void change(int *num) {  
4.     printf("Before adding value inside function num=%d \n",*num);  
5.     (*num) += 100;  
6.     printf("After adding value inside function num=%d \n", *num);  
7. }  
8.   
9. int main() {  
10.     int x=100;  
11.     clrscr();  
12.   
13.     printf("Before function call x=%d \n", x);  
14.     change(&x);//passing reference in function  
15.     printf("After function call x=%d \n", x);  
16.   
17.     getch();  
18.     return 0;  
19. }  

Output

Before function call x=100
Before adding value inside function num=100
After adding value inside function num=200
After function call x=200

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Difference between call by value and call by reference in c

No.	Call by value	Call by reference
1	A copy of value is passed to the function	An address of value is passed to the function
2	Changes made inside the function is not reflected on other functions	Changes made inside the function is reflected outside the function also
3	Actual and formal arguments will be created in different memory location	Actual and formal arguments will be created in same memory location

Recursion in C

When function is called within the same function, it is known as recursion in C. The function which calls the same function, is known as recursive function.

A function that calls itself, and doesn't perform any task after function call, is know as tail recursion. In tail recursion, we generally call the same function with return statement. An example of tail recursion is given below.

Let's see a simple example of recursion.

1. recursionfunction(){  
2.   
3. recursionfunction();//calling self function  
4.   
5. }  

Example of tail recursion in C

Let's see an example to print factorial number using tail recursion in C language.

1. #include<stdio.h>  
2. #include<conio.h>  
3. int factorial (int n)  
4. {  
5.     if ( n < 0)  
6.         return -1; /*Wrong value*/  
7.     if (n == 0)  
8.         return 1; /*Terminating condition*/  
9.     return (n * factorial (n -1));  
10. }  
11.   
12. void main(){  
13. int fact=0;  
14. clrscr();  
15. fact=factorial(5);  
16. printf("\n factorial of 5 is %d",fact);  
17.   
18. getch();  
19. }  

Output

factorial of 5 is 120

We can understand the above program of recursive method call by the figure given below:

Storage Classes in C

Storage classes are used to define scope and life time of a variable. There are four storage classes in C programming.

• auto
• extern
• static
• register

Storage Classes	Storage Place	Default Value	Scope	Life-time
auto	RAM	Garbage Value	Local	Within function
extern	RAM	Zero	Global	Till the end of main program, May be declared anywhere in the program
static	RAM	Zero	Local	Till the end of main program, Retains value between multiple functions call
register	Register	Garbage Value	Local	Within function

1) auto

The auto keyword is applied to all local variables automatically. It is the default storage class that is why it is known as automatic variable.

1. #include <stdio.h>  
2. void main(){  
3. int a=10;  
4. auto int b=10;//same like above  
5. printf("%d %d",a,b);  
6. }  

Output:

10 10

2) register

The register variable allocates memory in register than RAM. Its size is same of register size. It has a faster access than other variables.

It is recommended to use register variable only for quick access such as in counter.

Note: We can't get the address of register variable.

1. register int counter=0;  

3) static

The static variable is initialized only once and exists till the end of the program. It retains its value between multiple functions call.

The static variable has the default value 0 which is provided by compiler.

1. #include <stdio.h>  
2. void func() {  
3.    static int i=0;//static variable  
4.    int j=0;//local variable  
5.    i++;  
6.    j++;  
7.    printf("i= %d and j= %d\n", i, j);  
8. }  
9. void main() {  
10.   func();  
11.   func();  
12.   func();  
13. }  

Output:

i= 1 and j= 1
i= 2 and j= 1
i= 3 and j= 1

4) extern

The extern variable is visible to all the programs. It is used if two ore more files are sharing same variable or function.

1. extern int counter=0;  

C Array

Array in C language is a collection or group of elements (data). All the elements of c array are homogeneous (similar). It has contiguous memory location.

C array is beneficial if you have to store similar elements. Suppose you have to store marks of 50 students, one way to do this is allotting 50 variables. So it will be typical and hard to manage. For example we can not access the value of these variables with only 1 or 2 lines of code.

Another way to do this is array. By using array, we can access the elements easily. Only few lines of code is required to access the elements of array.

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Advantage of C Array

1) Code Optimization: Less code to the access the data.

2) Easy to traverse data: By using the for loop, we can retrieve the elements of an array easily.

3) Easy to sort data: To sort the elements of array, we need a few lines of code only.

4) Random Access: We can access any element randomly using the array.

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Disadvantage of C Array

1) Fixed Size: Whatever size, we define at the time of declaration of array, we can't exceed the limit. So, it doesn't grow the size dynamically like LinkedList which we will learn later.

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Declaration of C Array

We can declare an array in the c language in the following way.

1. data_type array_name[array_size];  

Now, let us see the example to declare array.

1. int marks[5];  

Here, int is the data_type, marks is the array_name and 5 is the array_size.

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Initialization of C Array

A simple way to initialize array is by index. Notice that array index starts from 0 and ends with [SIZE - 1].

1. marks[0]=80;//initialization of array  
2. marks[1]=60;  
3. marks[2]=70;  
4. marks[3]=85;  
5. marks[4]=75;  

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C array example

1. #include <stdio.h>    
2. #include <conio.h>    
3. void main(){    
4. int i=0;  
5. int marks[5];//declaration of array  
6. clrscr();    
7.   
8. marks[0]=80;//initialization of array  
9. marks[1]=60;  
10. marks[2]=70;  
11. marks[3]=85;  
12. marks[4]=75;  
13.   
14. //traversal of array  
15. for(i=0;i<5;i++){    
16. printf("%d \n",marks[i]);  
17. }//end of for loop  
18.   
19. getch();    
20. }    

Output

80
60
70
85
75

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C Array: Declaration with Initialization

We can initialize the c array at the time of declaration. Let's see the code.

1. int marks[5]={20,30,40,50,60};  

In such case, there is no requirement to define size. So it can also be written as the following code.

1. int marks[]={20,30,40,50,60};  

Let's see the full program to declare and initialize the array in C.

1. #include <stdio.h>    
2. #include <conio.h>    
3. void main(){    
4. int i=0;  
5. int marks[5]={20,30,40,50,60};//declaration and initialization of array  
6. clrscr();    
7.   
8. //traversal of array  
9. for(i=0;i<5;i++){    
10. printf("%d \n",marks[i]);  
11. }  
12.   
13. getch();    
14. }    

Output

20
30
40
50
60

Two Dimensional Array in C

The two dimensional array in C language is represented in the form of rows and columns, also known as matrix. It is also known asarray of arrays or list of arrays.

The two dimensional, three dimensional or other dimensional arrays are also known as multidimensional arrays.

Declaration of two dimensional Array in C

We can declare an array in the c language in the following way.

1. data_type array_name[size1][size2];  

A simple example to declare two dimensional array is given below.

1. int twodimen[4][3];  

Here, 4 is the row number and 3 is the column number.

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Initialization of 2D Array in C

A way to initialize the two dimensional array at the time of declaration is given below.

1. int arr[4][3]={{1,2,3},{2,3,4},{3,4,5},{4,5,6}};  

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Two dimensional array example in C

1. #include <stdio.h>    
2. #include <conio.h>    
3. void main(){    
4. int i=0,j=0;  
5. int arr[4][3]={{1,2,3},{2,3,4},{3,4,5},{4,5,6}};  
6. clrscr();    
7.   
8. //traversing 2D array  
9. for(i=0;i<4;i++){  
10.  for(j=0;j<3;j++){  
11.    printf("arr[%d] [%d] = %d \n",i,j,arr[i][j]);  
12.  }//end of j  
13. }//end of i  
14.   
15. getch();    
16. }    

Output

arr[0][0] = 1
arr[0][1] = 2
arr[0][2] = 3
arr[1][0] = 2
arr[1][1] = 3
arr[1][2] = 4
arr[2][0] = 3
arr[2][1] = 4
arr[2][2] = 5
arr[3][0] = 4
arr[3][1] = 5
arr[3][2] = 6

Passing Array to Function in C

To reuse the array operation, we can create functions that receives array as argument. To pass array in function, we need to write the array name only in the function call.

1. functionname(arrayname);//passing array  

There are 3 ways to declare function that receives array as argument.

First way:

1. return_type function(type arrayname[])  

Declaring blank subscript notation [] is the widely used technique.

Second way:

1. return_type function(type arrayname[SIZE])  

Optionally, we can define size in subscript notation [].

Third way:

1. return_type function(type *arrayname)  

You can also use the concept of pointer. In pointer chapter, we will learn about it.

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C language passing array to function example

1. #include <stdio.h>    
2. #include <conio.h>    
3. int minarray(int arr[],int size){  
4. int min=arr[0];  
5. int i=0;  
6. for(i=1;i<size;i++){  
7. if(min>arr[i]){  
8. min=arr[i];  
9. }  
10. }//end of for  
11. return min;  
12. }//end of function  
13.   
14. void main(){    
15. int i=0,min=0;  
16. int numbers[]={4,5,7,3,8,9};//declaration of array  
17. clrscr();    
18.   
19. min=minarray(numbers,6);//passing array with size  
20. printf("minimum number is %d \n",min);  
21.   
22. getch();    
23. }    

Output

minimum number is 3