1. 1. Character Set
A set of
valid character that a language recognises any letter symbol. A character
denotes any alphabet, digit or special symbol used to represent information.
Alphabet - A-Z
, a-z
Digit - 0-9
Symbol ! @
# $ % ^ () {}
[] ; , . > < ? / * etc.
White space enter backspace tab
2. 2. Token
The smallest individual unit of a program is called
token.
Types of Token
1. Keywords
2. Identifiers
3. Constant
4. String Constant
5. Special Symbol
6. Operator
2.1 Keywords
These are words whose meaning and use is predefined or
predecided.
For example-
|
asm |
else |
new |
this |
|
auto |
enum |
operator |
throw |
|
bool |
explicit |
Private |
true |
|
break |
export |
protected |
try |
|
case |
extern |
public |
typedef |
|
catch |
false |
register |
typeid |
|
char |
float |
reinterpret_cast |
typename |
|
class |
for |
return |
union |
|
const |
friend |
short |
unsigned |
|
const_cast |
goto |
signed |
using |
|
continue |
if |
sizeof |
virtual |
|
default |
inline |
static |
void |
|
do |
long |
struct |
wchar_t |
|
double |
mutable |
switch |
while |
|
dynamic_cast |
namespace |
template |
|
2.2 Identifiers
An identifiers is a name given by a user to a unit of
a program element name it can be variable name, function name, class name,
array name, structure name etc.
Rules of identifiers are
1.
Length is must be 1-31 character
2.
Only alphabet digit & underscore is used.
3.
First character must be an alphabet or an underscore
4.
Name can’t start with digit
5.
Keywords can’t be used
6.
Space & symbol are not allowed
7.
Upper case and lower case are different
Example -
Roll_no , BK_17 , _1ab ,_ab1
etc.
2.3 Constant
These are the data item that never change the value
during the program execution. It is 3 type
1. Integer
Constant
An integer is a whole number without any faction part
it can be +ve and –ve and default sign is +ve.
Example - 15
-33 +884
2. Floating
point/Real Constant
It is also known as real constant. It must have a
decimal value it must be +ve and –ve .It has two forms-
Fractional form - 2.0 17.50 etc.
Exponential form
200000 - 2.0e5
3. Character
Constant
It is single alphabet or a digit or a symbol in a
single inverted comma.
Example ‘a’
‘1’ ‘@’ etc.
2.4 String Constant
A string constant is a sequence of character in a
double quotation mark.
Example “hanuman”
“123456789” “#$%^&*()_+” etc.
2.5 Special Symbol
Special symbol are - () , {} , [] , . , , , / , \ , : , ; , ! , | etc.
3. Printf
Printf is an inbuilt library function in c which is
available in c library by default. This function is declared and related macros
are defined in “stdio.h” header file. Printf function is used to print the character,
string,
Float, integer, octal and hexadecimal values onto the output screen.
Example of Printf
#include<iostream.h>
#include<conio.h>
void main(){
clrscr();
cout<< ,cout<<"Hello" ,cout<<"Bye";
getch();
}
Output
ByeHello53
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