STRUCTURE

Structures are used to represent a record. Suppose you want to keep track of your books in a library. You might want to track the following attributes about each book −

• Title
• Author
• Subject
• Book ID

Defining a Structure

To define a structure, you must use the struct statement. The struct statement defines a new data type, with more than one member. The format of the struct statement is as follows −

struct Books {
   char  title[50];
   char  author[50];
   char  subject[100];
   int   book_id;
} book;  

Accessing Structure Members

To access any member of a structure, we use the member access operator (.). The member access operator is coded as a period between the structure variable name and the structure member that we wish to access. You would use the keyword struct to define variables of structure type.

Ex : student.number, book1.title

FILE PROCESSING

Opening Files

You can use the fopen( ) function to create a new file or to open an existing file. This call will initialize an object of the type FILE, which contains all the information necessary to control the stream.

Ex : FILE *f = fopen("data.txt","r");

#NB : r = read file

         w = write file

          a = append file

Closing a File

You can use the fclose() function to close an existing file

Ex : fclose(read), fclose(f)

FUNCTION AND RECURSION

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.

Ex : void check(){

      .....;

}

int check(int a,int b){

        ......;

        return ...;

}

Recursion is the process of repeating items in a self-similar way. In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.

Ex : 

void recursion(){

      recursion();

}

int recursion(int a, int b){

         recursion(a,b);   

         return ...;

}

ARRAY AND POINTER

A pointer is a variable whose value is the address of another variable, i.e., direct address of the memory location. Like any variable or constant, you must declare a pointer before using it to store any variable address.

Ex : int *a, char *ch

Arrays a kind of data structure that can store a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Ex : char str[100], double balance[20]

LOOPING / REPETITION

Repetisi dalam bahasa inggris sering disebut loops, biasanya digunakan untuk mengulang kode yang sama berkali-kali. Jumlah repetisinya itu beragam sesuai yang diinginkan, biasanya berisi ekspresi true/false.

Ada 3 variasi looping : while, do while, dan for.

While Looping : Repeats a statement or group of statements while a given condition is true. It tests the condition before executing the loop body.

Ex : while(...){

      ......;

}

Do While Looping : It is more like a while statement, except that it tests the condition at the end of the loop body. 

Ex : do{

     ......;

}while(....);

For Looping : Executes a sequence of statements multiple times and abbreviates the code that manages the loop variable.

Ex : for(...;...;...){

            ........;

}