LEARN WITH CLASSMATE: BASIC STRUCTURE OF C PROGRAM 1

The C program usually contain one or more sections.
To write a C program we first create a function main to accomplish a specific task
A function is a subroutine that contains the statements, enclosing them within { and } to perform the required task.
Except the function main(), rest of the sections are optional.
Different sections of a C-Program are shown below :

Contains comments such as : program description, programmer's name, date on which it is written and other details required by the program
A comment in a C program is ignored by the compiler
'/*' is used to mark the start of a comment and it terminate with '*/'
There must be no gap between the asterisk (*) and slash (/)
Comments are used to enhance program readability and understandability by giving the description or other detail about the program
Comments may be placed anywhere in the program, but are not allowed in the middle of any keyword or identifier

It helps to include the external file functions from the system library.

We must add an #include instruction in the program, which instructs the compiler to link the specified function in the library.

These library files are called as header files.

Header files can optionally be included in the program as per the requirement.

When we compile the C program,the header files are also compiled with the original program.

All the header files are included into the program by preprocessor directives.

Preprocessor directives are processed before a source program is handed over to the compiler.

these should be placed in a source program before the function main()

All the preprocessor directives should start with # and end without semicolon(;)

e.g:

All the standard mathematical functions (e.g : sin, cos, exp, etc.) are defined and kept as a part of C math library <math.h>

Some standard input/ output functions are defined in standard input/output header file, <stdio.h>

This section defines all the symbolic constants.
Symbolic constants are defined a value using the #define instruction.
Whenever a symbolic name is encountered, the compiler substitutes the value associated with the name automatically
The values remain constant throughout the program, and are not allowed to re define the values in the program
#define is a pre-processor directive
#define lines should not end with a semicolon (;)
Generally symbolic constants are written in uppercase

This section contains variables that are used more than one one function.

Any variable which is declared in this section is called as global variable and are available to all the functions

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