C Language / Variables, DataTypes and Constants
Variables
It is a data named used to store a data value and need declare the
variables for its types in c language.
Initialization of variables
Giving value to variables is called Initialization of variables.
Example
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Declaration
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Int x ;
|
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Initialization
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X=9;
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Declaration and Initialization
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Int x =9;
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Data Type
It tells the system / Computer to allocate how much space required by
the variable name and what type of variable it is.
C constants
| Constant Type
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Constant SubType
|
Example
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| Numeric |
Integer
|
5,12, 2, -2,4 |
| Real
|
23.12, 23.12 |
| Character |
single
|
‘A’,’w’,’e’,’s’ |
| Backslashcharacter
|
\b, \f, \n, \r e.t.c
|
| String
|
“Wisdom”, “Materials” |
|
Type
|
Size (bytes)
|
Format Specifier
|
|
int
|
at least 2, usually 4
|
%d
|
|
char
|
1
|
%c
|
|
float
|
4
|
%f
|
|
double
|
8
|
%lf
|
|
short int
|
2 usually
|
%hd
|
|
unsigned int
|
at least 2, usually 4
|
%u
|
|
long int
|
at least 4, usually 8
|
%li
|
|
long long int
|
at least 8
|
%lli
|
|
unsigned long int
|
at least 4
|
%lu
|
|
unsigned long long int
|
at least 8
|
%llu
|
|
signed char
|
1
|
%c
|
|
unsigned char
|
1
|
%c
|
|
long double
|
at least 10, usually 12 or 16
|
%Lf
|
Constants in c Language
It is a variable value cannot be changed. during the execution of a problem and is defined with const keyword in the c program.
Example
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const double PI = 3.14;
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ok
|
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const double PI = 3.14;
PI = 2.9;
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Error
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There are 2 types of constants in C.
Numeric and Character.
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Backslashcharacter/Escape Sequence character
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Meaning
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\b
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Backspace
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\f
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Form feed
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\n
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New line
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\r
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Carriage return
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\t
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Horizontal tab
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\”
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Double quote
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\’
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Single quote
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\\
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Backslash
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\v
|
Vertical tab
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\a
|
Alert or bell
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\?
|
Question mark
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