C Programming-Lecture Notes-02-Constants.pdf

B.Bhuvaneswaran, AP (SG) / CSE
9791519152
bhuvaneswaran@rajalakshmi.edu.in
Programming Logic
Constants

Constants
Constants Rajalakshmi Engineering College 2
Rajalakshmi Engineering College 2
Character Set
 The character set is a set of valid characters that a language can
recognize.
 A character represents any alphabet, digit or special symbols,
which can be used to form variables, numbers and expressions.

Constants
Character Set - Groups
 Letters / Alphabets
 Digits
 Special characters
 White spaces
Character
Set
Letters /
Alphabets
Digits
Special
Characters
White
Spaces

Constants
Character Set - Groups
Letters / Alphabets
Uppercase A . . . Z
Lowercase a . . . z
Digits All decimal digits 0 . . . 9
Special Characters
Comma , Ampersand &
Period . Caret ^
Semicolon ; Asterisk *
Colon : Minus sign -
Question mark ? Plus sign +
Apostrophe ‘ Opening angle bracket <
Quotation mark “ (or less than sign)
Exclamation mark ! Closing angle bracket >
Vertical bar | (or greater than sign)
Slash / Left parenthesis (
Backslash Right parenthesis )
Tilde ~ Left bracket [
Underscore _ Right bracket ]
Dollar sign $ Left brace {
Percent sign % Right brace }
Number sign #
White Spaces Blank space, Horizontal tab, Carriage return, New line, Form feed

Constants
Tokens
 In C program, the smallest individual units are known as C tokens.

Constants
Types of Tokens
 Keywords
 Identifiers
 Constants
 Strings
 Special symbols
 Operators

Constants
Examples
float
while
main
price
10
-12.15
“REC”
“cse”
[ ]
{ }
+ -
* /
Tokens
Keywords Identifiers Constants Strings
Special
Symbols
Operators

Constants
C Constants
 Constants in C refer to fixed values that do not change during the
execution of a program.

Constants
Integer Constants
 Integer constants are whole numbers (0 through 9) without any
fractional part.

Constants
Rules for Integer Constants
 An integer constant must have at least one digit and must not
have a decimal point.
 An integer constant may be positive or negative. If no sign is
preceded an integer constant, it is assumed to be positive.
 Embedded spaces, commas and non-digit characters are not
allowed.

Constants
Types of Integer Constants

Constants
Decimal Integer Constants
 Decimal integer constants can consist any combinations of digits
from 0 to 9, preceded by an optional + or – sign.

Constants
Examples
 Valid Examples:
0 +47 179
-240 22099
 Invalid Examples:
35 750 10,000 $5000 12.55

Constants
Octal Integer Constants
 Octal integer constants can consist of any combinations of digits
from 0 to 7.
 However, the first digit must be zero (0), in order to identify the
constant as an octal number.
 For instance, decimal integer 8 will be written as 010 as octal
integer.

Constants
Examples
 Valid Examples:
0 047 0240
01 70 010,000 $05000
012.55 0786

Constants
Hexadecimal Integer Constants
 Hexadecimal integer constants can consist of any combination of
digits from 0 to 9 and letters from A to F (either uppercase or
lowercase represents 10 to 15).
 A hexadecimal integer constant must begin with either 0x or 0X.
 For instance, decimal integer 12 will be written as 0XC or 0xc as
hexadecimal integer.

Constants
Examples
 Valid Examples:
0x 0X2 0x7A 0xbcd
0x35 75A 0x10,000 $0x5000
0x12.55 0x7AG

Constants
Real Constants
 Real constants are also called as floating point constants. Real
constants are numbers having fractional parts.

Constants
Forms of Real Constants
 Fractional form
 Exponential form

Constants
Fractional Form
 The fractional form consists of a series of digits representing the
whole part followed by a decimal point and series of digits
representing the floating part.
 The whole part or fractional part can be omitted, but not both.
 The decimal point cannot be omitted.

Constants
Rules for Fractional Form
 A real constant must have at least one digit and it must have a
decimal point.
 A real constant could be either positive or negative (default sign is
positive).
 Embedded spaces, commas and non-digit characters are not
allowed.

Constants
Examples
 Valid Examples:
0.0002 -0.96 179.47 +31.79
+.2 -.47 179. .99
12,000.50 31 12.30.45 $1000.75 15 750.25

Constants
Exponential Form
 The exponential (or scientific) form of representation of real
constants is usually used if the value of the constant is either too
small or too large.
 In exponential form of representation, the real constant is
represented in two parts namely, mantissa and exponent.
 Syntax:
mantissa e exponent
or
mantissa E exponent

Constants
Rules for Exponential Form
 The mantissa and the exponent should be separated by a letter e
(either uppercase or lowercase).
 The mantissa and exponent part may have a positive or negative
sign (default sign is positive).
 The mantissa and exponent part must have at least one digit.
 Embedded spaces, commas are not allowed.

Constants
Examples
 Valid Examples:
0.31e2 14e-3 3.1e+5 3.14E4
-1.2E-2
12,000e2 3.1e 2 3.1E+2.4

Constants
Single Character Constants
 A single character constant or a character constant consist of a
single character encloses within apostrophes i.e., single quotes (‘).

Constants
Rules for Single Character Constants
 A character constant is a single alphabet, a single digit, a single
special symbol or a blank space.
 The maximum length of a character constant can be one character.

Constants
Examples
 Valid Examples:
'B' 'V' '+' '$' ' '
'abc' '143'

Constants
String Constants
 A string constant is a sequence of characters encloses within
double quotation marks ("). Technically, a string is an array of
characters.
 The compiler automatically places the null character (0) at the
end of each such string, so the program can conveniently find the
end.

Constants
Rules for String Constants
 The string constant may be letters, numbers, special characters
and blank spaces.
 Every string constant ends up with a null character, which is
automatically assigned.

Constants
Examples
 Valid Examples:
"India" "2015" "WELCOME" "*.*"
"B" "$120"

Constants
Points to Remember
 A character constant 'B' is not the same as the string constant that
contains the single character "B". The former is the single
character and the later a character string consisting of character B
and 0 (null).
 A character constant as an equivalent integer value, whereas
single character string constant does not have an equivalent
integer value. It occupies two bytes, one for the ASCII code of B
and another for the null character with a value 0, which is used to
terminate strings.

Constants
Escape Sequences
 Certain constants are non-printable, which means that they are
not displayed on the screen or in the printer, called as escape
sequences (backslash character constants).
 C supports some special backslash character constants that are
used in output functions.

Constants
Escape Sequences
ASCII value Escape sequence Meaning
000 0 Null
007 a Audible alert (bell)
008 b Backspace
009 t Horizontal tab
010 n New line
011 v Vertical tab
012 f Form feed
013 r Carriage return
034 " Double quote
039 ' Single quote
063 ? Question mark
092 Backslash

C Programming-Lecture Notes-02-Constants.pdf

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