Rules for constructing Constants in C
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There are rules to be followed in order to create Constants in C. Let us discuss the rules to create constants.
Rules for constructing Integer Constants in C
1) An integer constant must have at least one digit.
2) It must not have a decimal point.
3) It can either be positive or negative.
4) No commas or blanks are allowed within an integer constant.
5) If no sign precedes an integer constant, it is assumed to be positive.
6) The allowable range for integer constants is -32768 to 32767
Actually, the range of the integer Constants in C depends on the compiler. The above mentioned range is for 16-bit compiler. However, for a 32-bit compiler the range would be even greater.
The integer constants
• Whole Numbers
• E.g. 25, 35, -25, -46
• For 16-bit C Compiler, Computer allocates only 2 bytes in memory.
• 16th bit is sign bit. (if 0 then positive value, if 1 then negative value)
Decimal Integer constant:
• 0 to 9
• E.g.: 49, 58, -62 … (40000 cannot come because it is > 32767)
Octal Integer constant:
• 0 to 7
• Add “0” before the value.
• E.g.: 045, 056, 067
Hexadecimal Integer constant:
• 0 to 9 and A to F
• Add 0x before the value
• E.g.: 0x42, 0x56, 0x67
Rules for constructing Real Constants in C
Rules for constructing Real constants (Fractional Form)
1) A real constant must have at least one digit
2) It must have a decimal point
3) It could be either positive or negative
4) If no sign precedes an real constant, it is assumed to be positive.
5) No commas or blanks are allowed within a real constant.
E.g.: +867.9, -26.9876, 654.0
Rules for constructing Real Constants (Exponential Form)
1) The mantissa part and the exponential part should be separated by the letter ‘e’
2) The mantissa may have a positive or negative sign(default sign is positive)
3) The exponent must have at least one digit
4) The exponent must be a positive or negative integer(default sign is positive)
E.g.: +3.2e-4, 4.1e8, -0.2e+4, -3.2e-4
Rules for constructing Character Constants in C
1) A character constant is an alphabet, a single digit or a single special symbol enclosed within single quotation. For example, ‘S’ is a valid character constant whereas “S” is not as it is enclosed within double quotation.
2) The maximum length of a character constant can be 1 character. C Compiler allots 1 byte of memory
E.g.: ’B’, ’l’, ’#’
To learn more about constants in C, visit – Variable, constant and keyword in C