Unit 4

1. Explain designing structure program

Structured Programming Approach, as the word suggests, can be defined as a programming approach in which the program is made as a single structure. It means that the code will execute the instruction by instruction one after the other. It doesn’t support the possibility of jumping from one instruction to some other with the help of any statement like GOTO, etc. Therefore, the instructions in this approach will be executed in a serial and structured manner. The languages that support Structured programming approach are:

• C
• C++
• Java
• C#

..etc

On the contrary, in the Assembly languages like Microprocessor 8085, etc, the statements do not get executed in a structured manner. It allows jump statements like GOTO. So the program flow might be random.

The structured program mainly consists of three types of elements:

• Selection Statements
• Sequence Statements
• Iteration Statements

The structured program consists of well structured and separated modules. But the entry and exit in a Structured program is a single-time event. It means that the program uses single-entry and single-exit elements. Therefore a structured program is well maintained, neat and clean program. This is the reason why the Structured Programming Approach is well accepted in the programming world.

Advantages of Structured Programming Approach:

1. Easier to read and understand
2. User Friendly
3. Easier to Maintain
4. Mainly problem based instead of being machine based
5. Development is easier as it requires less effort and time
6. Easier to Debug
7. Machine-Independent, mostly.

Disadvantages of Structured Programming Approach:

1. Since it is Machine-Independent, So it takes time to convert into machine code.
2. The converted machine code is not the same as for assembly language.
3. The program depends upon changeable factors like data-types. Therefore it needs to be updated with the need on the go.
4. Usually the development in this approach takes longer time as it is language-dependent. Whereas in the case of assembly language, the development takes lesser time as it is fixed for the machine.

2.     Explain with example defining and declaring a function

A function is a group of statements that together perform a task. Every C program has at least one function, which is main(), and all the most trivial programs can define additional functions.

You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division is such that each function performs a specific task.

A function declaration tells the compiler about a function's name, return type, and parameters. A function definition provides the actual body of the function.

The C standard library provides numerous built-in functions that your program can call. For example, strcat() to concatenate two strings, memcpy() to copy one memory location to another location, and many more functions.

A function can also be referred as a method or a sub-routine or a procedure, etc.

Defining a Function

The general form of a function definition in C programming language is as follows −

Return_type function_name( parameter list ) {

   body of the function

}

A function definition in C programming consists of a function header and a function body. Here are all the parts of a function −

• Return Type − A function may return a value. The return_type is the data type of the value the function returns. Some functions perform the desired operations without returning a value. In this case, the return_type is the keyword void.
• Function Name − This is the actual name of the function. The function name and the parameter list together constitute the function signature.
• Parameters − A parameter is like a placeholder. When a function is invoked, you pass a value to the parameter. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the parameters of a function. Parameters are optional; that is, a function may contain no parameters.
• Function Body − The function body contains a collection of statements that define what the function does.

Example

Given below is the source code for a function called max(). This function takes two parameters num1 and num2 and returns the maximum value between the two −

/* function returning the max between two numbers */

Int max(int num1, int num2) {

   /* local variable declaration */

   int result;

   if (num1 > num2)

      result = num1;

   else

      result = num2;

   return result;

}

Function Declarations

A function declaration tells the compiler about a function name and how to call the function. The actual body of the function can be defined separately.

A function declaration has the following parts −

Return_type function_name( parameter list );

For the above defined function max(), the function declaration is as follows −

Int max(int num1, int num2);

Parameter names are not important in function declaration only their type is required, so the following is also a valid declaration −

Int max(int, int);

Function declaration is required when you define a function in one source file and you call that function in another file. In such case, you should declare the function at the top of the file calling the function.

3.     What is signature of function?

A function signature (or type signature, or method signature) defines input and output of functions or methods.

A signature can include:

• Parameters and their types
• a return value and type
• Exceptions that might be thrown or passed back
• Information about the availability of the method in an object-oriented program (such as the keywords public, static, or prototype).

4.     Write in brief parameter and return type of a function

So a function either can take some arguments, or nothing is taken. Similarly, a function can return something, otherwise does not return anything. So we can categorize them into four types.

• Function with No argument and No return type.
• Function with No argument and Return something.
• A function that takes argument but returns nothing.
• Functions that take an argument and also return something.

Example

#include <stdio.h>

Void my_function() {

Printf("This is a function that takes no argument, and returns nothing.");

}

Main() {

My_function();

}

Output

This is a function that takes no argument, and returns nothing.

Here this function is not taking any input argument, and also the return type is void. So this returns nothing.

Example

#include <stdio.h>

Int my_function() {

Printf("This function takes no argument, But returns 50\n");

Return 50;

}

Main() {

Int x;

x = my_function();

Printf("Returned Value: %d", x);

}

Output

This function takes no argument, But returns 50

Returned Value: 50

Here this function is not taking any input argument, but its return type is int. So this returns a value.

Example

#include <stdio.h>

Void my_function(int x) {

Printf("This function is taking %d as argument, but returns nothing", x);

Return 50;

}

Main() {

Int x;

x = 10;

My_function(x);

}

Output

This function is taking 10 as argument, but returns nothing

Here this function is taking an input argument, but its return type is void. So this returns nothing.

Example

#include <stdio.h>

Int my_function(int x) {

Printf("This will take an argument, and will return its squared value\n");

Return x * x;

}

Main() {

Int x, res;

x = 12;

Res = my_function(12);

Printf("Returned Value: %d", res);

}

Output

This function is taking 10 as argument, but returns nothing

Here this function is taking any input argument, and also returns value.

5.     Explain passing parameters to function with example

This is the default way of passing the parameters to the function. This is achieved by passing the copy of data to the function. This mechanism is also called as call by value. In case of parameter passing by value, the changes made to the formal arguments in the called function have no effect on the values of actual arguments in the calling function.

This mechanism is used when programmer don't want to change the value of passed parameters. When parameters are passed by value then functions in C create copies of the passed in variables and do required processing on these copied variables.

Pass-by-value is implemented by actual data transfer so additional storage is required to maintain the copies of passed parameters.

Example:

Output :

Before: Value of a = 10 and value of b = 20

Value of a (p1) = 20 and value of b (p2) = 10

After: Value of a = 10 and value of b = 20

Note: In the above example the values of “a” and “b” remain unchanged before calling swap function and after calling swap function.

6.     What is call by value explain in brief?

The function called at program startup is named main . The main function can be defined with no parameters or with two parameters (for passing command-line arguments to a program when it begins executing). The two parameters are referred to here as argc and argv, though any names can be used because they are local to the function in which they are declared.

A main function has the following syntax:

Int main(void) { . . . }

Int main(int argc, char *argv[ ]) { . . . })

Argc

The number of arguments in the command line that invoked the program. The value of argc is nonnegative.

Argv

Pointer to an array of character strings that contain the arguments, one per string. The value argv[argc] is a null pointer.

If the value of argc is greater than zero, the array members argv[0] through argv[argc - 1] inclusive contain pointers to strings, which are given implementation-defined values by the host environment before program startup. The intent is to supply the program with information determined before program startup from elsewhere in the host environment.

If the host environment cannot supply strings with letters in both uppercase and lowercase, the host environment ensures that the strings are received in lowercase.

If the value of argc is greater than zero, the string pointed to by argv[0] represents the program name; argv[0][0] is the null character if the program name is not available from the host environment.

If the value of argc is greater than one, the strings pointed to by argv[1] through argv[argc –

1] represent the program parameters.

The parameters argc and argv, and the strings pointed to by the argv array, can be modified by the program and keep their last-stored values between program startup and program termination.

In the main function definition, parameters are optional. However, only the parameters that are defined can be accessed.

7.     Explain passing array to function with example

In C, there are various general problems which requires passing more than one variable of the same type to a function. For example, consider a function which sorts the 10 elements in ascending order. Such a function requires 10 numbers to be passed as the actual parameters from the main function. Here, instead of declaring 10 different numbers and then passing into the function, we can declare and initialize an array and pass that into the function. This will resolve all the complexity since the function will now work for any number of values.

As we know that the array_name contains the address of the first element. Here, we must notice that we need to pass only the name of the array in the function which is intended to accept an array. The array defined as the formal parameter will automatically refer to the array specified by the array name defined as an actual parameter.

Consider the following syntax to pass an array to the function.

1. Functionname(arrayname);//passing array  

Methods to declare a function that receives an array as an argument

There are 3 ways to declare the function which is intended to receive an array as an 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 a pointer. In pointer chapter, we will learn about it.

C language passing an array to function example

1. #include<stdio.h>  
2. Int minarray(int arr[],int size){    
3. Int min=arr[0];    
4. Int i=0;    
5. For(i=1;i<size;i++){    
6. If(min>arr[i]){    
7. Min=arr[i];    
8. }    
9. }//end of for    
10. Return min;    
11. }//end of function    
12.    
13. Int main(){      
14. Int i=0,min=0;    
15. Int numbers[]={4,5,7,3,8,9};//declaration of array    
16.  
17. Min=minarray(numbers,6);//passing array with size    
18. Printf("minimum number is %d \n",min);    
19. Return 0;  
20. }    

Output

Minimum number is 3

8.     Write a program to sort the array

C function to sort the array

1. #include<stdio.h>   
2. Void Bubble_Sort(int[]);  
3. Void main ()    
4. {    
5.    Int arr[10] = { 10, 9, 7, 101, 23, 44, 12, 78, 34, 23};     
6.    Bubble_Sort(arr);    
7. }    
8. Void Bubble_Sort(int a[]) //array a[] points to arr.   
9. {  
10. Int i, j,temp;     
11.    For(i = 0; i<10; i++)    
12.    {    
13.        For(j = i+1; j<10; j++)    
14.        {    
15.            If(a[j] < a[i])    
16.            {    
17.                Temp = a[i];    
18.                a[i] = a[j];    
19.                a[j] = temp;     
20.            }     
21.        }     
22.    }     
23.    Printf("Printing Sorted Element List ...\n");    
24.    For(i = 0; i<10; i++)    
25.    {    
26.        Printf("%d\n",a[i]);    
27.    }  
28. }  

Output

Printing Sorted Element List ...

7 

9 

10 

12 

23

23 

34 

44 

78 

101 

9.     Explain Returning array from the function with example

As we know that, a function can not return more than one value. However, if we try to write the return statement as return a, b, c; to return three values (a,b,c), the function will return the last mentioned value which is c in our case. In some problems, we may need to return multiple values from a function. In such cases, an array is returned from the function.

Returning an array is similar to passing the array into the function. The name of the array is returned from the function. To make a function returning an array, the following syntax is used.

1. Int * Function_name() {  
2. //some statements;   
3. Return array_type;  
4. }  

To store the array returned from the function, we can define a pointer which points to that array. We can traverse the array by increasing that pointer since pointer initially points to the base address of the array. Consider the following example that contains a function returning the sorted array.

1. #include<stdio.h>   
2. Int* Bubble_Sort(int[]);  
3. Void main ()    
4. {    
5.    Int arr[10] = { 10, 9, 7, 101, 23, 44, 12, 78, 34, 23};     
6.    Int *p = Bubble_Sort(arr), i;  
7.    Printf("printing sorted elements ...\n");  
8.    For(i=0;i<10;i++)  
9.    {  
10.        Printf("%d\n",*(p+i));  
11.    }  
12. }    
13. Int* Bubble_Sort(int a[]) //array a[] points to arr.   
14. {  
15. Int i, j,temp;     
16.    For(i = 0; i<10; i++)    
17.    {    
18.        For(j = i+1; j<10; j++)    
19.        {    
20.            If(a[j] < a[i])    
21.            {    
22.                Temp = a[i];    
23.                a[i] = a[j];    
24.                a[j] = temp;     
25.            }     
26.        }     
27.    }     
28.    Return a;  
29. }  

Output

Printing Sorted Element List ...

7 

9  

10 

12 

23

23 

34 

44 

78

101 

10. Explain passing pointers to function.

C programming allows passing a pointer to a function. To do so, simply declare the function parameter as a pointer type.

Following is a simple example where we pass an unsigned long pointer to a function and change the value inside the function which reflects back in the calling function −

#include <stdio.h>

#include <time.h>

Void getSeconds(unsigned long *par);

Int main () {

   unsigned long sec;

   getSeconds( &sec );

   /* print the actual value */

   printf("Number of seconds: %ld\n", sec );

   return 0;

}

Void getSeconds(unsigned long *par) {

   /* get the current number of seconds */

   *par = time( NULL );

   return;

}

When the above code is compiled and executed, it produces the following result −

Number of seconds :1294450468

The function, which can accept a pointer, can also accept an array as shown in the following example −

#include <stdio.h>

/* function declaration */

Double getAverage(int *arr, int size);

Int main () {

   /* an int array with 5 elements */

   int balance[5] = {1000, 2, 3, 17, 50};

   double avg;

   /* pass pointer to the array as an argument */

   avg = getAverage( balance, 5 ) ;

   /* output the returned value  */

   printf("Average value is: %f\n", avg );

   return 0;

}

Double getAverage(int *arr, int size) {

   int  i, sum = 0;      

   double avg;         

   for (i = 0; i < size; ++i) {

      sum += arr[i];

   }

   avg = (double)sum / size;

   return avg;

}

When the above code is compiled together and executed, it produces the following result −

Average value is: 214.40000