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, etcOctal : 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
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