Short Notes: Elements of C | Short Notes for Computer Science Engineering - Computer Science Engineering (CSE) PDF Download

 Page 1


ELEMENTS OF C
Every language has some basic elements & grammatical rules. Before starting with programming, 
we should be acquainted with the basic elements that build the language.
Character Set
Communicating with a computer involves speaking the language the computer understands. In C, 
various characters have been given to communicate.
Character set in C consists of;
Types Character Set
Lower case a-z
Upper case A-Z
Digits 0-9
Special Character !@#$%A &*
White space Tab or new lines or space
Keywords
Keywords are the words whose meaning has already been explained to the C compiler. The 
keywords cannot be used as variable names because if we do so we are trying to assign a new 
meaning to the keyword, which is not allowed by the computer.
There are only 32 keywords available in C. Below figure gives a list of these keywords for your 
ready reference.
KEYWORDS
auto do goto
signed unsigned
break double if sizeof void
case else int
static volatile
char enum long struct
w hile
const extern
register switch
continue
float return typeodef
default
for short union
Page 2


ELEMENTS OF C
Every language has some basic elements & grammatical rules. Before starting with programming, 
we should be acquainted with the basic elements that build the language.
Character Set
Communicating with a computer involves speaking the language the computer understands. In C, 
various characters have been given to communicate.
Character set in C consists of;
Types Character Set
Lower case a-z
Upper case A-Z
Digits 0-9
Special Character !@#$%A &*
White space Tab or new lines or space
Keywords
Keywords are the words whose meaning has already been explained to the C compiler. The 
keywords cannot be used as variable names because if we do so we are trying to assign a new 
meaning to the keyword, which is not allowed by the computer.
There are only 32 keywords available in C. Below figure gives a list of these keywords for your 
ready reference.
KEYWORDS
auto do goto
signed unsigned
break double if sizeof void
case else int
static volatile
char enum long struct
w hile
const extern
register switch
continue
float return typeodef
default
for short union
Identifier
In the programming language C, an identifier is a combination of alphanumeric characters, the 
first being a letter of the alphabet or an underline, and the remaining being any letter of the 
alphabet, any numeric digit, or the underline.
Two rules must be kept in mind when naming identifiers.
1 . The case of alphabetic characters is significant. Using "INDEX" for a variable is not the 
same as using "index" and neither of them is the same as using "InDeX" for a variable. All 
three refer to different variables.
2. As C is defined, up to 32 significant characters can be used and will be considered 
significant by most compilers. If more than 32 are used, they will be ignored by the 
compiler.
Data Type
In the C programming language, data types refer to a domain of allowed values & the operations 
that can be performed on those values. The type of a variable determines how much space it 
occupies in storage and how the bit pattern stored is interpreted. There are 4 fundamental data 
types in C, which are- char, int, float &, double. Char is used to store any single character; int is 
used to store any integer value, float is used to store any single precision floating point number & 
double is used to store any double precision floating point number. We can use 2 qualifiers with 
these basic types to get more types.
There are 2 types of qualifiers-
Sign qualifier- signed & unsigned 
Size qualifier- short & long
The data types in C can be classified as follows:
Type
Storage size Value range
char 1 byte -128 to 127
unsigned char 1 byte 0 to 255
int 2 or 4 bytes -32,768 to 32,767 or -2,147,483,648 to 2,147,483,647
unsigned int 2 or 4 bytes 0 to 65,535 or 0 to 4,294,967,295
short 2 bytes -32,768 to 32,767
unsigned short 2 bytes 0 to 65,535
Page 3


ELEMENTS OF C
Every language has some basic elements & grammatical rules. Before starting with programming, 
we should be acquainted with the basic elements that build the language.
Character Set
Communicating with a computer involves speaking the language the computer understands. In C, 
various characters have been given to communicate.
Character set in C consists of;
Types Character Set
Lower case a-z
Upper case A-Z
Digits 0-9
Special Character !@#$%A &*
White space Tab or new lines or space
Keywords
Keywords are the words whose meaning has already been explained to the C compiler. The 
keywords cannot be used as variable names because if we do so we are trying to assign a new 
meaning to the keyword, which is not allowed by the computer.
There are only 32 keywords available in C. Below figure gives a list of these keywords for your 
ready reference.
KEYWORDS
auto do goto
signed unsigned
break double if sizeof void
case else int
static volatile
char enum long struct
w hile
const extern
register switch
continue
float return typeodef
default
for short union
Identifier
In the programming language C, an identifier is a combination of alphanumeric characters, the 
first being a letter of the alphabet or an underline, and the remaining being any letter of the 
alphabet, any numeric digit, or the underline.
Two rules must be kept in mind when naming identifiers.
1 . The case of alphabetic characters is significant. Using "INDEX" for a variable is not the 
same as using "index" and neither of them is the same as using "InDeX" for a variable. All 
three refer to different variables.
2. As C is defined, up to 32 significant characters can be used and will be considered 
significant by most compilers. If more than 32 are used, they will be ignored by the 
compiler.
Data Type
In the C programming language, data types refer to a domain of allowed values & the operations 
that can be performed on those values. The type of a variable determines how much space it 
occupies in storage and how the bit pattern stored is interpreted. There are 4 fundamental data 
types in C, which are- char, int, float &, double. Char is used to store any single character; int is 
used to store any integer value, float is used to store any single precision floating point number & 
double is used to store any double precision floating point number. We can use 2 qualifiers with 
these basic types to get more types.
There are 2 types of qualifiers-
Sign qualifier- signed & unsigned 
Size qualifier- short & long
The data types in C can be classified as follows:
Type
Storage size Value range
char 1 byte -128 to 127
unsigned char 1 byte 0 to 255
int 2 or 4 bytes -32,768 to 32,767 or -2,147,483,648 to 2,147,483,647
unsigned int 2 or 4 bytes 0 to 65,535 or 0 to 4,294,967,295
short 2 bytes -32,768 to 32,767
unsigned short 2 bytes 0 to 65,535
long 4 bytes -2,147,483,648 to 2,147,483,647
unsigned long 4 bytes 0 to 4,294,967,295
Type
Storage size Value range Precision
float 4 bytes 1.2E-38 to 3.4E+38 6 decimal places
double 8 bytes 2.3E-308 to 1.7E+308 15 decimal places
long double 10 bytes 3.4E-4932 to 1.1E+4932 19 decimal places
Constants
A constant is an entity that doesn’t change whereas a variable is an entity that may change.
C constants can be divided into two major categories:
• Primary Constants
• Secondary Constants
Here our only focus is on primary constant. For constructing these different types of constants 
certain rules have been laid down.
Rules for Constructing Integer Constants:
An integer constant must have at least one digit.
a) It must not have a decimal point.
b) It can be either positive or negative.
Page 4


ELEMENTS OF C
Every language has some basic elements & grammatical rules. Before starting with programming, 
we should be acquainted with the basic elements that build the language.
Character Set
Communicating with a computer involves speaking the language the computer understands. In C, 
various characters have been given to communicate.
Character set in C consists of;
Types Character Set
Lower case a-z
Upper case A-Z
Digits 0-9
Special Character !@#$%A &*
White space Tab or new lines or space
Keywords
Keywords are the words whose meaning has already been explained to the C compiler. The 
keywords cannot be used as variable names because if we do so we are trying to assign a new 
meaning to the keyword, which is not allowed by the computer.
There are only 32 keywords available in C. Below figure gives a list of these keywords for your 
ready reference.
KEYWORDS
auto do goto
signed unsigned
break double if sizeof void
case else int
static volatile
char enum long struct
w hile
const extern
register switch
continue
float return typeodef
default
for short union
Identifier
In the programming language C, an identifier is a combination of alphanumeric characters, the 
first being a letter of the alphabet or an underline, and the remaining being any letter of the 
alphabet, any numeric digit, or the underline.
Two rules must be kept in mind when naming identifiers.
1 . The case of alphabetic characters is significant. Using "INDEX" for a variable is not the 
same as using "index" and neither of them is the same as using "InDeX" for a variable. All 
three refer to different variables.
2. As C is defined, up to 32 significant characters can be used and will be considered 
significant by most compilers. If more than 32 are used, they will be ignored by the 
compiler.
Data Type
In the C programming language, data types refer to a domain of allowed values & the operations 
that can be performed on those values. The type of a variable determines how much space it 
occupies in storage and how the bit pattern stored is interpreted. There are 4 fundamental data 
types in C, which are- char, int, float &, double. Char is used to store any single character; int is 
used to store any integer value, float is used to store any single precision floating point number & 
double is used to store any double precision floating point number. We can use 2 qualifiers with 
these basic types to get more types.
There are 2 types of qualifiers-
Sign qualifier- signed & unsigned 
Size qualifier- short & long
The data types in C can be classified as follows:
Type
Storage size Value range
char 1 byte -128 to 127
unsigned char 1 byte 0 to 255
int 2 or 4 bytes -32,768 to 32,767 or -2,147,483,648 to 2,147,483,647
unsigned int 2 or 4 bytes 0 to 65,535 or 0 to 4,294,967,295
short 2 bytes -32,768 to 32,767
unsigned short 2 bytes 0 to 65,535
long 4 bytes -2,147,483,648 to 2,147,483,647
unsigned long 4 bytes 0 to 4,294,967,295
Type
Storage size Value range Precision
float 4 bytes 1.2E-38 to 3.4E+38 6 decimal places
double 8 bytes 2.3E-308 to 1.7E+308 15 decimal places
long double 10 bytes 3.4E-4932 to 1.1E+4932 19 decimal places
Constants
A constant is an entity that doesn’t change whereas a variable is an entity that may change.
C constants can be divided into two major categories:
• Primary Constants
• Secondary Constants
Here our only focus is on primary constant. For constructing these different types of constants 
certain rules have been laid down.
Rules for Constructing Integer Constants:
An integer constant must have at least one digit.
a) It must not have a decimal point.
b) It can be either positive or negative.
c) If no sign precedes an integer constant it is assumed to be positive.
d) No commas or blanks are allowed within an integer constant.
e) The allowable range for integer constants is -32768to 32767.
Ex.: 426, +782,-8000, -7605
Rules for Constructing Real Constants:
Real constants are often called Floating Point constants. The real constants could be written in 
two forms—Fractional form and Exponential form.
Rules for constructing real constants expressed in fractional form:
a) A real constant must have at least one digit.
b) It must have a decimal point.
c) It could be either positive or negative.
d) Default sign is positive.
e) No commas or blanks are allowed within a real constant.
Ex. +325.34, 426.0, -32.76, -48.5792
Rules for constructing real constants expressed in exponential form:
a) The mantissa part and the exponential part should be separated by a letter e.
b) The mantissa part may have a positive or negative sign.
c) Default sign of mantissa part is positive.
d) The exponent must have at least one digit, which must be a positive or negative integer. 
Default sign is positive.
e) Range of real constants expressed in exponential form is -3.4e38 to 3.4e38.
Ex. +3.2e-5, 4.1e8, -0.2e+3, -3.2e-5
Rules for Constructing Character Constants:
a) A character constant is a single alphabet, a single digit or a single special symbol enclosed 
within single inverted commas.
b) The maximum length of a character constant can be 1 character.
Ex.: ‘M’, ‘6’, ‘+’