Some common rules for writing C program

Remember Some common rules for writing C program

• Use all commands or statements in lower or small case.
• After completion of a statement excluding main() or loops must insert ; (semicolon) as a statement terminator.
• Don’t use/declare identifier or variable name same as statement name suppose int include; this is a wrong statement because include has a special meaning in the language.
• Header Files or Preprocessor Directives contains references or links of library functions. That is built-in in the C language.

Suppose if you want to use a function clrscr() ; in the main function so must be declared on top # include other wise you could have an prototype error.

Some header files are as follows

• Stdio.h
• Conio.h
• Dos.h
• String.h
• Stdlib.h

And many more header files are available in C…

void main(void)
Every C programs consists of one or more functions. No matter how many
functions there are in a C program , main is the one to which control is passed
from the operating system when the program is run ; it is the first function
executed. The word “void” preceding “main” specifies that the function main()
will not return a value. The second “void,” in parenthesis , specifies that the
function takes no arguments.
printf()
printf() is built-in function we can display with printf() any message, variable
value on screen/file/printer.
In printf() we can use many escape sequences and format specifies.

Escape sequences are special notations through which we can display our data
Variety of ways:

Some escape sequences and their functions are as follows:
Escape Sequence    Description                                                   Example

\n                        Perform line feed & Carriage return operation       printf(“A\nB”);

\t                        Prints a tab sequence on screen                          printf (“A\tb”);

\’                         Prints a single quote character on screen          printf (“\’a\’”);

\”                         Prints a double quote character on Screen                printf (“\”a\”");

\r                         Perform carriage return operation                         printf (“a\rb”)

\b                         Remove one character from left                          printf (“a\bHi!” );

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