Structure of C program

Before starting understanding the Structure of C program, we need to know what are instructions?

C programming language for beginners from ShreyaSingh291866

What is C programming language.

Character set in C Programming Language 

Instructions

Instructions are very much similar to sentences/statements in English language. It is the combination of various tokens, character set elements to perform a desired task/output to help a program make it complete.

OR

Instructions in C are the commands in the program that will instruct C compiler to perform specific tasks or actions. Whenever we write a C instruction, we are telling C compiler to do a task for us.

Structure of C program

Following are the categories of instructions:

1. Declaration instructions
2. Input/output instructions
3. Assignment instructions
4. Arithmetic/logical instructions
5. Control instructions

1- Declaration instructions

These are used to declare different kind of variable further to be used by the C program.

Eg:- we want to make a program and declare the variable suppose, we want to write the area of rectangle. So the declaration is 

int A, B, Area;

       OR

int l, b, area;

We want to add two numbers, then the declarations is

int A, B, sum;

2- Input/output instructions

Input instructions are used for supplying values to the variables as declared in declarative instructions.

Eg:-   (Statically supplying the values to the variables)

          

              A=10;

              B=20;

Where the values of variables are fixed.

 

     (for dynamically supplying the value)

  then we use a C library function called scanf( )

 output instructions are used for printing the output after the execution of instructions.

Then we use a C library function called printf( );

3- Assignment instructions

These are used for assigning the values in proper order to the variables.

 int A, B, C;

 printf(“Enter the first number”);

 scanf(“%d”,&A);

 printf(“Enter the second number”);

 scanf(“%d”,&B);

 printf(“Enter the third number”);

 scanf(“%d”,&C);

 

4-  Arithmetic instructions / Logical instructions

These are used for applying the arithmetic formula or logic to solve the problems.

Eg:- we need to give a logical instruction to out program

 area=l * b;

OR

 area = A * B;

5- Control instructions

These are used to control the flow of execution of the program.

Data types in C

Ranges of Data types in C

Our first C program

 stdio.h

Standard input output header  file 

This header files contains the definition of standard

Input output functions used by a C program.

Eg:-  printf( );                scanf( );

             |                             |

             |                             |

             |                             |

    output           input 

 conio.h

Console input ouput header file

This header file contains the definition of standard input output functions used by C program related to console input output devices.

Eg:- keyboard for input 

       monitor for output

The function needed for supplying the input data via keyboard and to get output data via monitor are defined inside <conio.h> library header  file.

            clrscr( );    Clear the screen

            getch( );     Get character

 void main( )

C compiler starts its compilation from main( ).

Before compilation these is another process known as pre-processing takes place.

During pre-processing, the header files are to be declared in this section.

Some important points to be noted while you make any program

1. C program is case sensitive
2. All the statements are end with semicolon ( ; ) 
3. You must have to include header files 
4. Space values are ignored in C.