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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


Structured Datatypes

  • A structure in C is a collection of items of different types. You can think of a structure as a "record" is in Pascal or a class in Java without methods.

  • Structures, or structs, are very useful in creating data structures larger and more complex than the ones we have discussed so far.

  • Simply you can group various built-in data types into a structure.

  • Object concepts was derived from Structure concept. You can achieve few object oriented goals using C structure but it is very complex.

Following is the example how how to define a structure.

struct student
{
char firstName[20];
char lastName[20];
char SSN[9];
float gpa;
};

Now you have a new datatype called student and you can use this datatype define your variables of student type:

struct student student_a, student_b;

or an array of students as

struct student students[50];

Another way to declare the same thing is:

struct {
char firstName[20];
char lastName[20];
char SSN[10];
float gpa;
} student_a, student_b;

All the variables inside an structure will be accessed using these values as student_a.firstName will give value of firstName variable. Similarly we can access other variables.

Structure Example:
Try out following example to understand the concept:

#include <stdio.h>
struct student {
char firstName[20];
char lastName[20];
char SSN[10];
float gpa;
};

main()
{
struct student student_a;

strcpy(student_a.firstName, "Deo");
strcpy(student_a.lastName, "Dum");
strcpy(student_a.SSN, "2333234" );
student_a.gpa = 2009.20;

printf( "First Name: %s\n", student_a.firstName );
printf( "Last Name: %s\n", student_a.lastName );
printf( "SNN : %s\n", student_a.SSN );
printf( "GPA : %f\n", student_a.gpa );
}

This will produce following results:

First Name: Deo
Last Name: Dum
SSN : 2333234
GPA : 2009.

Pointers to Structs:
Sometimes it is useful to assign pointers to structures (this will be evident in the next section with self-referential structures). Declaring pointers to structures is basically the same as declaring a normal pointer:

struct student *student_a;

To dereference, you can use the infix operator: ->.

printf("%s\n", student_a->SSN);

typedef Keyword
There is an easier way to define structs or you could "alias" types you create. For example:

typedef struct{
char firstName[20];
char lastName[20];
char SSN[10];
float gpa;
}student;

Now you can use student directly to define variables of student type without using struct keyword. Following is the example:

student student_a;

You can use typedef for non-structs:

typedef long int *pint32;

pint32 x, y, z;

x, y and z are all pointers to long ints

Unions Datatype
Unions are declared in the same fashion as structs, but have a fundamental difference. Only one item within the union can be used at any time, because the memory allocated for each item inside the union is in a shared memory location.

Here is how we define a Union

union Shape
{
int circle;
int triangle;
int ovel;
};

We use union in such case where only one condition will be applied and only one variable will be used.

Conclusion:
You can create arrays of structs.
Structs can be copied or assigned.
The & operator may be used with structs to show addresses.
Structs can be passed into functions. Structs can also be returned from functions.
Structs cannot be compared!
Structures can store non-homogenous data types into a single collection, much like an array does for common data (except it isn't accessed in the same manner).
Pointers to structs have a special infix operator: -> for dereferencing the pointer.
typedef can help you clear your code up and can help save some keystrokes.

NEXT >> Working With Files

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