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  C Programming Tutorials
Basics of C:
Facts about C
Why to Use C
C Program File
C Compilers

Program Structure:
Simple C Program
C Program Compilation

Basic DataTypes:
DataTypes
Modifiers
Qualifiers
Arrays

Variable Types:
Local Variable
Global Variable

Storage Classes:
auto storage class
register storage class
static storage class
extern storage class

Using Constants:
Defining Constants
The enum Data Types

Operator Types:
Arithmetic Operators
Logical Operators
Bitwise Operators
Assignment Operators
Misc Operators

Control Statements:
Branching
Looping

Input and Output:
printf() function
scanf() function

Pointing to Data:
Pointers and Arrays
Pointer Arithmetic
Pointer Arithmetic with arrays

Functions:
Using functions
Declaration and Definition

Strings:
Reading and Writing Strings
String Manipulation Function

Structured DataTypes:
Structure
Pointer to Structure

Working with Files:
Files
Basic I/O

Bits:
Bits Manipulation
Bits Field

Pre-Processors:
Pre-Processors Examples
Parameterized Macros
Macro Caveats

Useful Concepts

Built-in Library Functions:
String Manipulation Function
Memory Management Function
Buffer Manipulation
Character Functions
Error Handling Functions

Soft Skills
Communication Skills
Leadership Skills
                              .........More

 

 

  

C Programming Tutorials


Declaration and Definition
When a function is defined at any place in the program then it is called function definition. At the time of definition of a function actual logic is implemented with-in the function.

A function declaration does not have any body and they just have their interfaces.

A function declaration is usually declared at the top of a C source file, or in a separate header file.

A function declaration is sometime called function prototype or function signature. For the above Demo() function which returns an integer, and takes two parameters a function declaration will be as follows:

int Demo( int par1, int par2);

Passing Parameters to a Function
There are two ways to pass parameters to a function:

  • Pass by Value: mechanism is used when you 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 Reference mechanism is used when you want a function to do the changes in passed parameters and reflect those changes back to the calling function. In this case only addresses of the variables are passed to a function so that function can work directly over the addresses.

Here are two programs to understand the difference: First example is for Pass by value:

#include <stdio.h>

/* function declaration goes here.*/
void swap( int p1, int p2 );

int main()
{
int a = 10;
int b = 20;

printf("Before: Value of a = %d and value of b = %d\n", a, b );
swap( a, b );
printf("After: Value of a = %d and value of b = %d\n", a, b );
}

void swap( int p1, int p2 )
{
int t;

t = p2;
p2 = p1;
p1 = t;
printf("Value of a (p1) = %d and value of b(p2) = %d\n", p1, p2 );
}

Here is the result produced by the above example. Here the values of a and b remain unchanged before calling swap function and after calling swap function.

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

Following is the example which demonstrate the concept of pass by reference

#include <stdio.h>

/* function declaration goes here.*/
void swap( int *p1, int *p2 );

int main()
{
int a = 10;
int b = 20;

printf("Before: Value of a = %d and value of b = %d\n", a, b );
swap( &a, &b );
printf("After: Value of a = %d and value of b = %d\n", a, b );
}

void swap( int *p1, int *p2 )
{
int t;

t = *p2;
*p2 = *p1;
*p1 = t;
printf("Value of a (p1) = %d and value of b(p2) = %d\n", *p1, *p2 );
}

Here is the result produced by the above example. Here the values of a and b are changes after calling swap function.

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 = 20 and value of b = 10

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