Integer Constant in C language

Integer constant 

‘‘What is an integer? Explain giving example.”

Definition: An integer constant is a whole number without any decimal point. No extra characters are allowed other than + and –sign. If + and – are present, they should precede the  number. An integer constant can be classified into three types as shown below.

Integer Constants are

Decimal : e.g: 120,14,-1, etc
Octal   : e.g : 070,012,-040, etc.
Hexadecimal : e.g. 0xBA, 0x3B etc


Now, let us explain decimal integer with example.
Definition: A decimal integer can be any combination of digits from ‘0’ to ‘9’. No extra characters are allowed other than ‘+’ and ‘–’ sign. If ‘+’ and ‘–’are present. Then they should precede the integer. For example, 100,-7,+989 etc.The following are invalid:


Decimal Integers
Validity
Reasons for Invalidity
10,000
invalid
Comma is not allowed.
0.5
invalid
Decimal point is not allowed.
10 20
invalid
Space is not allowed.
085
invalid
Should not start with the digit 0.
32768
invalid
Out of range for 16 bit machine.
-32769
invalid
Out of range for 16 bit machine.

Now let us see ‘‘What is an octal number? Explain giving example.’’

Definition: An octal integer constant can be any combination of digits from ‘0’ to ‘7’ with a Prefix 0(digit zero).No extra characters are allowed other than preceding ‘+’ and ‘- ’ sign. For Example, 01612, 034567, -0765 etc. are valid. The following are invalid:

Octal Integers
Validity
Reasons for invalidity
7,000
Invalid
Comma is not allowed.
0.075
Invalid
Decimal point is not allowed.
10 20
Invalid
Space is not allowed.
085
Invalid
8 is invalid in octal.
275
Invalid
Should have a prefix 0.



Now, let us see ‘‘What is a hexadecimal number? Explain giving example.’’

Definition: An hexadecimal integer constant can be any combination of digits from ‘0’ to ‘9’ along with the letters ‘A’ to ‘F’ or ‘a’ to ‘f’. This constant has be preceded OX or OX. For example, 0x18A, OXB, OXFFF etc. are valid. The following are invalid hexadecimal constant:

Hexadecimal Integers
Validity
Reasons for invalidity
10,000
invalid
Comma is not allowed.
0xIJ
invalid
I and J are invalid characters.
Ox123
invalid
Should be preceded with 0(zero) not O(Oh.)
O1234
invalid
Should be preceded with 0x or OX.




Note: usually decimal integers are used in programming. Octal and hexadecimal  are rarely used.
Floating point constant
Integer Constant in C language Integer Constant in C language Reviewed by Bill Smithwick on October 19, 2013 Rating: 5

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