Basic Structure of C Program – C Tutorial #3

A ‘C’ program is divided into six sections: Documentation, Link, Definition, Global Declaration, Main() Function, Subprograms. While the main section is compulsory, the rest are optional in the structure of the C program.

Three Major things which Should Consider

  1. Firstly, think about what should be the output?
  2. Then, think about what should be the inputs that will be required to produce this output.
  3. And Last, think about the steps of instructions which use these inputs to produce required output.

Structure of C program

The structural parts of C program

  • Documentation section
  • Preprocessor section
  • Definition section
  • Global declaration
  • Main function
  • User defined functions

Explanation of Structure of C Programming by an Example.

C Program To Find Your Age

A simple C Program

Simple C Program

Explanation of Above C Program

#include<stdio.h>

  • This is a reference to a special file which is also known as the header file called stdio.h.
  • stdio.h contains information that must be included in the program when it is compiled.
  • The #include statement tells the compiler to include the input/output library or Header file (stdio.h) in the program.
  • It is present at the beginning of almost every C program.

Basically, all the statements starting with # in a C program are called preprocessor directives. This statement allows you to use some predefined functions such as, printf (), in this case.

int main()

  • Every C program contains a function called main().
  • This is the starting point of the program. This is the point from where the execution begins.
  • It will usually call other functions to help to performs its job, some that we write and others from the standard libraries provided.
  • main () declares the start of the function/while the curly brackets() shows the sent and finish of the function. Curly brackets in Care used to group statement together as a function, on in the body of a loop. Such a grouping is known as a compound statement on a block.
  • Every statement within a function ends with a terminator semicolon (;).
  • int is the return value of the main function and instead of int we can use void which means having no return type.

printf(“www.PrabhakarGuru.com \n”);

  • The printf is a function which is defined in the stdio.h file and is used to prints the words on the screen.
  • The text to be printed is enclosed in double quotes and put inside brackets.
  • The message is quoted because in C a text (also known as String or a sequence of charaters) is always put between inverted commas.
  • The \n is an escape sequence at the end of the text tells the program to print a newline as part of the output. That means now if we give a second printf statement, it will be printed in the next line.

/* Comments in C Program */

  • Comments may appear anywhere within a program, as long as they are placed within the delimitres /* and */.
  • Such comments are helpful in identifying the program’s principal features or in explaining the underlying logic of vanous program features.
  • These are non executable statement as they are not executed by the compiler.
  • // is used to comment a single statement. This is known as line comment whereas /* is ended with */is used to comment multiple statement. The comment inside it is known as block comment.

return 0;

  • After all the statement in the program have been written, the last statement of the program will be return statement which will return an integer value 0 to the operating system indicating that there were no errors during the execution of the program.
  • In case of void main we don’t need to write return 0.

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