BASICS OF C PART 2
Statements: C programs are made of functions. Functions contain
statements. Statement performs a specific action and terminated by semicolon
‘;’ . In the above program
printf(“Welcome to C
programming”); is only statement.
You can write printf statement in multiple line . for example. :
The statement:
printf(“ The increasing popularity of C is
probably”
“
Due to its many desirable quantities/.”
“It is a robust language whose
rich set is “);
is a single statement.
The Second program:
1.
/*
program2.c */
2.
/*This
program accepts a character two number and displays them in screen */
3.
#include<stdio.h>
4.
main()
5.
{
6.
char c; int i;
7.
float f;
8.
printf(“\nEnter a character:”);
9.
Scanf(“%c”,&c);
10. printf(“\nEnter an integer;”);
11. scanf(“%d”,&i);
12. printf(“\nEnter a floating pt number:”);
13. scanf(“%f”,&f);
14. printf(“character: %c\n integeris:%d,float:
%f”,c,i,f);
15. } /*end of main() */
Analysis:Variable and types:
Line number 6 and 7
in program are:
char c; int i; and float f;
In those lines,
c,i, f are variables and int, char, float are data types key words for declaration of variables in C
program.
In C there are four
primitive types of variables.
- char : it can store
one ASCII character(i.e. one byte only )
- int: it can store integers(
i.e. without decimal precision values). Its size is generally 2 bytes.
However it differs from machine to machine. In some machines it is equal
to 4 bytes. If it is two bytes it can store numbers from -32768 to +32767
- float : Single
precision number with decimal value. Its size is generally equal to 4
bytes.
- double: Double
precision number with decimal value. Its size is generally equal to 8
bytes.
How these types are
indicated in printf and scanf functions ?
- char : by %c
- int : by %d(decimal) , %i (integer) , %x(hex) ,
%o (octal)
- float : by %f
- double : by %f
in C each necessary
variable is declared before its use. If
variable is declared outside the function, it is called global variable and
visible to all the functions in that program. If variable is declared inside
the function it is called local variable and visible only for that particular
function only.
How to give the
variable name ?
There some
restrictions on naming the variables in C.
- Variable name should
begin with a alphabetic character. But
underscore character ‘_’ is also legal character as beginning
character for variable name.
- Variable name should
contain only letters ,digits and underscore characters. No other
characters are allowed for name.
- Variable name should
be unambiguous within its first eight characters since first eight
characters are treated as significant characters by many compilers.
- Uppercase and
lowercase are significant. i.e.
name, Name,NAME or nAme all are different variables.
- The C key word can not
be a variable name.
- White spaces are not
allowed
Here are some
examples of valid and invalid variable names in C.
Valid variable
names:
Abc, name ,
_name, first_name alpha_1,
alpha99 alp97bc etc
Invalid varieable name:
(Why ?)
123_res, first name, ret?b first-name
ab:xy, % int return
The declaration of variables
is done as:
<data type > <variable name> ;
we can declare more than one
variable of same type with single type declaration as:
char var1,var2,var3,……,varn;
float e,f,g; and so on.
The scanf() function:
Scanf() is an input
function defined in stdio.h header file. Scanf accepts the input from keyboard. As above programs the
syntax of input function scanf is
Scanf(“specifier”,&variablename);
The
specifier may be any one of %d,%c,%f and so on.
The & is an address operator in scanf function . &variablename specifies the memory
address for the variable and the value entered from keyboard is stored in that
specified location.
Recall the line 14 of
program:
printf(“character: %c\n
integer:%d,float: %f”,c,i,f);
if our input is :
c=’A’, i=10,and f=23.45
This produces the
output as:
character: A
integer : 10
float : 23.450000
The specifier
%c,%d,%f etc inside the double quote of the printf
statement displays the actual value of variable listed after the closing of
double quote and comma ‘,’ sequentially. If there are no listing of variables
for those specifier, then the some garbage value is printed.
Using Pression specifiers in the display of
float numbers.
You may have
noticed that the floating point number example
in above program 2 have displayed
with more decimal places in them than
were in original number. You can exercise greater control over how a float
number is displayed using precision specifier to limit the number the number of
decimal places displayed.
For example the variable x contains the number 23.456789
and you only want two of its decimal
places for display the printf statement looks like
Printf(“%5.2f”,x);
which will produce out put as 23.45
Field width precision
Similary you can print the integer numbers with interleaving spaces
using specifiers.
Example: int x=10,y=40,z=30;
If the printf statement in program is :
printf(“%d%d%d”,x,y,z); then the output
is : 104030 which is ambiguous.
You can print it in meaningful
format using formatted printf statement
as:
printf (“%4d%4d%5d”,x,y,z); which gives output as: 10
40 30
The Third Program:
1. /* progm3.c */
2. /*this program illustrates the simple
arithmetic and assignment operators */
3. #include<stdio.h>
4. main()
5. {
6. int
num1,num2,sum,dif,prod, rem;
7. float div;
8. printf(“\nEnter the firsrt number:”);
9. scanf(“%d”,&num1);
10.
printf(“\nEnter the second number: “);
11.
scanf(“%d”,&num2);
12.
sum=num1+num2;
13.
dif=num1-num2;
14.
prod=num1*num2;
15.
div=(float)num1/(float)num2;
16.
printf(“The sum is %d”, sum);
17.
printf(“\nThe difference of %d and %d is %d
“,
num1,num2,dif);
18.
printf(“\n%d x %d = %d “ ,num1,num2,prod);
19.
printf(“\nThe quotient after division is %f”, div);
20.
printf(“\nThe remainder dividing %d with %d
is : %d”,
num1,num2,num1%num2);
21.
}
/*end of program */
Arithmetic
operators in C:
+ for addition
-
for subtraction
* for
multiplication
/ for division
% for remainder ( only for integer division )
Assignment
Operator:
= for assign the value to a variable.
e. g.
int x = 10;
float f = 56.34;
char c = ‘n’; /* character constant is included inside single quote */
short-cut assignment:
+=, -=, *= , /=
eg. x= x+10
equivalent to x+=10
var1 = var1 * var2 equivalent to var1*=var2 ………….and so on
Constants:
Constants are those
that don’t changes during the whole program execution.
Constants are
defined in C by the following two ways.
- using #define directive:
syntax : #define identifier value /* note no
semicolon */
e.g. #define PI 3.14
#define ADULT_AGE 18
#define GREETING “Wishing you Happy Dashain “
2. Using const key word:
syntax: <const> <data type> identifier = value
;
eg. const
float PI = 3.14;
const
char ch = ‘#’;
Expressions:
Expressions are combinations of variables ,constants and operators
arranged as per the grammar of the language. C can handle any complex types of expressions . some
example of mathematical expressions in C are as shown.
Algrabic expression C
expression
ab – c a*b-c
(m+n) (x+y) (m+n)
* (x+y)
|
a*b/c
 |
3x2+2x-1 3*x*x
+2*x – 1
|
x c
y
Note: There is no any operator
in C for exponentiation.
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