Fundamentals of C
Identifiers:
Identifier refers to the name of variables, function and
array. These are user-defined names and consist of sequence of letters and
digits with a letter as a first character. C is case sensitive (i.e. upper and
lower case) letters are treated differently. Thus, the names rate, RATE and
Rate denote different identifiers.
Keywords:
Keywords are the reserved words in programming language for
doing specific task. These have predefined meaning and cannot be changed by the
user.
There are 32 keywords in C language. Some are:
Int for else
Float do void
Char while case
Double if default
Header files:
Header file ( also called as include file) contains
declarations of data types, keywords, predefined identifiers, operators and the
library functions. To include header file in the program, we have to use
pre-processor directive
i.e.
#include
e.g.
#include<stdio.h>
It tells the compiler to include the additional source file.
i.e. stdio.h (standard input output file) to the program. The header file must
be included to the beginning of all programs that use input/output statements.
Data types:
Data can be of many types e.g. character, integer, real or
string. Hence, data types specifies the size and type of data.
These are four fundamental/basic types in C, they are:
1. Integer data types:
Integers are whole numbers having no fractional parts such
as 5, 8, -7. Integers are represented by int
keyword. C supports three types of integer namely short int, int and long int in
both signed and unsigned forms.
Types size (in bit)
Short int 16
Int 16
Long int 32
2. Floating point data
types: A number having fractional
part is a floating point numbers. Eg.3012 floating point number is represented
by float keyword. Its size is 32
bits with 6 digits of precision (precision refers to the number of significant
digits after the decimal point).
2. Double Data Types:
The double data type is also used for handling floating
point numbers. But, it occupies twice as much memory as type float i.e. 64 bits
with 14 digits of precision.
When the accuracy provided by a float number is not
sufficient, the type double can be used. The keyword double is used for double precision floating point numbers.
4. Character Data Type:
A single character can be defined as a character type data
which maximum size is 8 bits long. The char
keyword is used to represent character data type.
Variable:
Variable is a memory location used to store data value.
Every variable in C has a data types and it must be declared before it is used
in a program. The value of variable may change during the execution of a
program. There are certain rules regarding variable names which are listed
below:
1. It should begin with letter not with digit
2. It can't be a keyword
3. Space not allowed
4. Uppercase and lower case are distinct.
5. It should not be of length more than 32 characters.
Declaration of
Variable
The declaration of variables must be done before they are
used in the program. The declaration statement defines the name and data type
of variable.
The syntax for declaring a variable is:
Data_type variable_name1, variable_name2... ;
e.g.
int a,b,c;
float d,e;
Note: variables
of the same data type are separated by commas. A declaration must end with a
semicolon.
Constant - (literal)
Constant is also a memory location used to store data
values. Unlike variable, its value does not change during program execution.
Types:
1. Integer constant:
It is a whole number that has no decimal part e.g. 1, 50.
2. Floating point or Real constant:
It is a number having fractional part e.g. 12.50,50.100 etc.
3. Character constant:
A character enclosed within single quotes is known as
character constant. E.g. a, A, b.
4. String Constant/ Literal:
A string literal is a sequence of characters enclosed within
double quotes. E.g. "RAM", "C is the best".
Operator:
An operator is a symbol that tells the computer to perform
certain mathematical or logical operation.
Unary operator requires
single variable(operand) to calculate final answer whereas Binary Operator requires two variable (operand) to calculate a
final answer.
C operators can be classified into a number of categories.
They include:
1. Arithmetic Operator:
The operators used for arithmetic operation (i.e. addition,
subtraction, multiplication) are called arithmetic operator. A list of
arithmetic operators and their meaning are given below.
Operator Meaning
+ Addition
- subtraction
* multiplication
/ division
% module
division (remainder of an integer division)
Note: The module
operator (%) produces the remainder of dividing the first by the second
operand. But, both the operands must be integer data types. It can't be used
with float or double data types.
e.g. if a & b are integers and a= 14 and b= 4 then
a%b = 2 (reminder of an integer division)
2. Relational operators:
The relational operators are used to compare the value
between the two operands(variable) and return the appropriate result. If the
comparison is true, it returns 1 and if the comparison is false, it returns
false or 0.
Hence, depending on their relation, it helps to take certain
decision after comparison.
Operator Meaning
> greater
than
< less
than
>= greater
than or equal to
<= less
than or equal to
== equal
to
!= not
equal to
e.g.
the expression 3>4 results false whereas the expression
5<6 results true.
3. Logical
Operators:
Logical operators combine two or more relational
expressions. C has the following three logical operators:
Operators Meaning
&& logical
AND
|| logical
OR
! ogical
NOT
NOTE: The logical
AND operator (&&) gives net result TRUE only if both the conditions
have value TRUE otherwise give result FALSE.
The OR operator (||) gives net result TRUE even if one of
the condition has value TRUE. But, if both the conditions have false value, it
result FALSE.
The logical NOT operator (!) takes single expression and
results to TRUE if the expression is false and results to FALSE if the
expression is true. In other words, it just reverses the value of the
expression.
4. Assignment Operator:
It is used to assign a value or result of an expression to a
variable. The symbol "=" is used as assignment operator. There are
arithmetic assignment operators which combine an arithmetic operator and an
assignment operator they are:
+=, -=, /=, *=, %=
e.g.
a+=b; is equal to a=a+b
a-=b; is equal to a=a-b
a*=b; is equal to a=a*b
a/=b; is equal to a=a/b
a%=b; is equal to a=a%b
5. Increment
& Decrement Operator:
Increment and decrement operator are unary operator because
they operate on one operand(variable). Increment operator (++) adds 1 the
operand while decrement operator (--) subtracts 1 from its operand. These
operators can be used in two ways: postfix and prefix forms(or operators).
e.g. a++ increment operator as a postfix operator
++aa increment operator as a prefix operator
a-- decrement operator as a postfix
operator
--a decrement operator as a prefix
operator
6. Conditional
Operators:
Conditional operator is only the
ternary operator i.e. it requires three expression as operands. The general
form of conditional operator (?:)is:
Test expression? Expression1:
expression2
If test expression is true, then
the value of whole expression is the value of expression 2 otherwise the value
of whole expression is the value of expression 3 e.g.
A=10;
B=15;
X=(a>b)?a:b;
In this case, x will be assigned
the value of b i.e. 15.
C Statements:
Statements represent a set of
declaration or step in sequence of actions. It is the instruction given to the
computer to perform any kind of action. All the statement end with semicolon.
e.g.
int a,b,c;
c=a+b;
The value above statement causes
the computer to carry out addition of the variable a and b and assign the
result to c.
No comments:
Post a Comment