❮ C Fun Pointer Callback C Data Types ❯

Basic Syntax

We have already seen the basic structure of a C program, which will help us understand other basic building blocks of the C language.

Tokens in C

A C program consists of various tokens, which can be keywords, identifiers, constants, string literals, or symbols. For example, the following C statement contains five tokens:

printf("Hello, World! \n");

These five tokens are:

printf
(
"Hello, World! \n"
)
;

Semicolon ;

In a C program, a semicolon is a statement terminator. That is, each individual statement must be ended with a semicolon. It indicates the end of a logical entity.

For example, here are two different statements:

printf("Hello, World! \n");
return 0;

Comments

C language has two ways of commenting:

// Single-line comment

A single-line comment starting with // can occupy a single line.

/* Single-line comment */
/* 
   Multi-line comment
   Multi-line comment
   Multi-line comment
 */

The /* */ format of comments can be single-line or multi-line.

You cannot nest comments within comments, and comments cannot appear within a string or character literal.

Identifiers

C identifiers are names used to identify variables, functions, or any other user-defined item. An identifier starts with a letter A-Z or a-z or an underscore _ followed by zero or more letters, underscores, and digits (0-9).

Punctuation characters such as @, $, and % are not allowed within C identifiers. C is a case-sensitive programming language. Therefore, in C, Manpower and manpower are two different identifiers. Here are some valid identifiers:

mohd       zara    abc   move_name  a_123
myname50   _temp   j     a23b9      retVal

Keywords

The following table lists the reserved words in C. These reserved words cannot be used as constant names, variable names, or other identifier names.

Keyword	Description
auto	Declare automatic variable
break	Break out of current loop
case	Switch statement branch
char	Declare character variable or function return type
const	Define constant; if a variable is modified by const, its value cannot be changed
continue	End current loop, begin next iteration
default	Default branch in switch statement
do	Loop body
double	Declare double precision floating-point variable or function return type
else	Conditional statement negative branch (used with if)
enum	Declare enumeration type
extern	Declare variable or function defined elsewhere
float	Declare floating-point variable or function return type
for	A type of loop
goto	Unconditional jump statement
if	Conditional statement
int	Declare integer variable or function
long	Declare long integer variable or function return type
register	Declare register variable
return	Subroutine return statement (can take parameters or not)
short	Declare short integer variable or function
signed	Declare signed type variable or function
sizeof	Calculate size of data type or variable (in bytes)
static	Declare static variable
struct	Declare structure type
switch	Used for switch statement
typedef	Used to give a type a new name
unsigned	Declare unsigned type variable or function
union	Declare union type
void	Declare function with no return value or no parameters, or declare void pointer
volatile	Indicates that a variable can be changed implicitly
while	Loop condition for loop statement

C99 Added Keywords

C11 Added Keywords

Whitespace in C

A line containing only whitespace, possibly with a comment, is known as a blank line, and the C compiler completely ignores it.

In C, whitespace is used to describe blank spaces, tabs, newline characters, and comments. Whitespace separates different parts of a statement so that the compiler can identify where one element of a statement (like int) ends and the next begins. Therefore, in the statement:

int age;

Here, int and age must be separated by at least one whitespace character (usually a space), so the compiler can distinguish between them. On the other hand, in the statement:

fruit = apples + oranges;   // Get the total number of fruits

The whitespace characters between fruit and =, or = and apples are not necessary, but you can add them as needed to enhance readability.

❮ C Fun Pointer Callback C Data Types ❯