Character set: Character set
are the set of alphabets, numbers and some special characters that are valid in
C language. Character set consists of following elements:
1) Alphabets: A to Z and a to z
2) Digits: 0 1 2 3 4 5 6 7 8 9
3) Special
Characters:
|
,
|
<
|
>
|
.
|
_
|
(
|
)
|
;
|
$
|
:
|
%
|
[
|
]
|
#
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?
|
|
'
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&
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{
|
}
|
"
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^
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!
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*
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/
|
|
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-
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\
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~
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+
|
|
Comment: Comments are the statement that are used to declare how
the following code works and make code easy to understand. Comment has no
effect on programs runs.
Two types of
comments:
a.
Line Comment: A comment denoted
by double forward slash (//). Eg. //This
is variable
b.
Block Comment: To comment on some blocks in a program, starting by
forward slash asterisk (/*) write multiple lines of comment and ending asterisk
forward slash (*/).
Example. /* It takes two values and compare between them
Example. /* It takes two values and compare between them
And generate greatest number. */
White space
Characters: Blank space,
new line, horizontal tab, carriage return and form feed
Keywords: Keywords are
the reserved words used in programming. Each keyword has standard, fixed
meaning and that cannot be changed by user.
For example: int
money;
Here, int is a
keyword that indicates, 'money' is of type integer.
C programming
is case sensitive; all keywords must be written in lowercase. Here is the list of all keywords
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auto
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double
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int
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struct
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void
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signed
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continue
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goto
|
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break
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else
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long
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switch
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while
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static
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do
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if
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|
case
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enum
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register
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typedef
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volatile
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sizeof
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default
|
const
|
|
char
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extern
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return
|
union
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unsigned
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for
|
short
|
static
|
Identifiers: Identifiers are
names given to various program elements such as constants, variables,
functions, structures, array etc. Each element in the program has its own
unique name.
For example:
int money;
int mango_tree;
Here, money
is a identifier which denotes a variable of type integer. Similarly, mango_tree
is an identifier, which denotes variable of type integer.
Rules for
writing identifier
- An Identifiers consists of letters (both uppercase and lowercase letters), digits and and underscore '_' only.
- The first letter of identifier should be either a letter or an underscore.
Example: int a,
_b; where a and _b are valid identifier.
Tokens: In C source
code, the basic element recognized by the compiler is known as tokens. A token
is source program text that the compiler does not break down into components
elements. Keyword like int, float; constant like a, b; string literals like
name, address; operators like &&, ||.
Data types: A program
usually contains different types of data types (integer, float, character etc)
and need to store the values being used in the program. There are two types of
data type
- Primary Data Types: The basic fundamental of data having unit features is called primary data type.
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Data
Types
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Types
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Memory
Require
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Format
|
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void
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Void
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0
byte
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|
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char
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Character
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1
byte
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%c
|
|
int
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Integer
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4/2 bytes
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%d
|
|
float
|
Floating
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4
bytes
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%f
|
|
long
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Floating
number
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4
bytes
|
|
|
double
|
Large
floating point number
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8
bytes
|
%lf
|
|
long
double
|
Very
large floating number
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12
bytes
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%lf
|
- Secondary Data Types: The data types which is constructed by merging some features of primary data types.
- arrays (a[ ]) 2. pointer (*p) 3. structures (struct)
- enumeration (enum) 5. union (union)
Variables and Constants
Variables: Variables are memory location in computer's memory to store data. To indicate the memory location, each variable should be given a unique name called identifier. Variable names are just the symbolic representation of a memory location Examples of variable name: sum, car_no, count etc.
int num;
Here, num is a variable of integer type.
Three types of variables:
Static variable declaration: Any variable which is declared by using keyword
static is called static variable. The value of static variable is remain fixed
for the other function but may changes within same function boundary.
Example:
#include <stdio.h>
#include <conio.h>
void func() {
static int x = 0;
/* x is initialized only once across three calls of func() and the variable will get incremented three times after these calls. The final value of
x will be 3. */
printf("%d\n", x); // outputs the value of x
x++;
}
int main() { //int
argc, char *argv[] inside the main is optional in the particular program
func(); //
prints 0
func();
// prints 1
func();
// prints 2
func();
// prints 3
// return
0;
getch();
}
Global variable declaration: Any variable which is declared before main function
is called global variable.
Example: int a=20; //global
variables
main
( )
{
int
a= 5;
{
}
Local variable declaration: Any variable which is declared within the function is
called local variable.
Example:
#include<stdio.h>
#include<conio.h>
main( )
{
int a=9,b=4,c;
// local variable
c=a+b;
printf("c=%d\n",c);
getch( );
}
Rules for writing variable name in C
- Variable name can be composed of letters (both uppercase and lowercase letters), digits and underscore '_' only.
- The first letter of a variable should be either a letter or an underscore.
- There is no rule for the length of length of a variable.
In C programming, you have to declare variable before
using it in the program.
Declaration of variables
The variable declaration syntax is
data_type
variable_name assignment
_operator value_to_variable
Example:
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data_type
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variable_name
|
assignment _operator
|
value_to_variable
|
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int
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a
|
|
|
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float
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pi
|
=
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3.14
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Constants
Constants are the terms that can't be changed during
the execution of a program.
There are 2 types of constants
1. Numeric
a. Integer Constant: The numeric constant that does not
contain decimal point is called integer constant.
Example:
8, -12
b. Floating-point constant: The numeric constant that contain fractional number (having decimal point). For example: -2.00, 0.0000222
2.
Character
a. Character
constant: The constant that contains a single character is called character
constant. It is enclosed inside the single quotation mark. For example: 'a', 'l', 'm', 'F' etc.
b. String Constant: The constant that contain
alpha-numeric value enclosed in a pair of double-quote marks. For example:
"good" //string constant
"" //null string constant
" " //string constant of six white space
"x" //string constant having single character.
"Earth is round\n" //prints string with newline
Types of
Specifier:
1) Escape Sequence:
These nonprintable characters are used to format text on the output screen.
Escape sequence are always started with backslash (\) causes "escape"
from the normal way the characters are interpreted by the compiler. For
example:
\n is used for newline.|
Escape
Sequences
|
Character
|
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\b
|
Backspace
|
|
\f
|
Form
feed
|
|
\n
|
Newline
|
|
\r
|
Return
/ Enter
|
|
\t
|
Horizontal
tab
|
|
\v
|
Vertical
tab
|
|
\\
|
Backslash (It
print single \)
|
|
\'
|
Single
quotation mark (It
print ')
|
|
\a
|
Bell ( It
produces audible sound i.e. beep)
|
|
\"
|
Double
quotation mark. (It
print ")
|
|
\?
|
Question
mark
(It print ?)
|
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\0
|
Null
character
|
2) Format Specifier: The output and input data are display and receive in specific pattern. Format specifier uses the token % and character(s) after it.
|
Format
Specifier
|
Used
by scanf () function
|
|
%d,
% i
|
Single
integer
|
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%u
|
Unsigned
integer
|
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%f
|
Floating
point number
|
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%x
|
Hexadecimal
number, lower for character
|
|
%X
|
Hexadecimal
number, upper for character
|
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%c
|
Character
|
|
%s
|
String
|
Example:
printf("Name is
%s, Class is %d, Section is %c", "Puja", 12, 'A');
Output: Name is Puja,
Class is 12, Section is A
Statement: A smallest executable entity
within a program is called statement. Statements are the basic building block
of C programming language. These statements enable the computer to carry out
some calculation or perform logical comparison between values and variables.
A programming
statement may consist of keyword, constant, variables, operators, control
statements, data types, library function, and user-defined functions.
Any
line written in C editor that normally terminates by a semicolon (;) is called
statement
Example:
int a=5, 6;
Types of statements
a.
Simple
Statement: A
simplest executable entity is called simple statement. It is a single line
expression which is used to carry out assignment, calculation or test logical
decision
b. Compound statement: A single instruction composed of
two or more individual instructions.
This type of statement is used to
combine two or more statement in one single line of code.
#include <stdio.h>
#include<conio.h>
main
( )
{
float pi, r, a; // simple statement
pi = 3.1415; // simple statement
r= 4.5;
a =pi* r*r; // compound statement,
calculate and assign value to a
printf("%f is the area of
circle having radius %f", a, r);
getch( );
}
c. Control statement: A statement that affects the flow
of execution of program is called control statement. Two types of control
statements
1.
Selection (There are five selection control statement. They
are if, if-else, nested if-else, if-else-if, and switch)
2.
Iteration
(There are 3 types of iteration control statement. They are for, while and do
-while)
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