Recently , we learned about C constant , variable and keywords . Now we have to combine them to form instructions .
Lets do this :
/* Multiplication of floating and integer number */
#include<stdio.h>
int main ()
{
int P ;
float R;
P = 500 ;
Q = 8.5
R = P * Q ; /* Multiplication */
printf("%f\n", R) ;
return 0;
}
Let understand the above program in detail .
Form above C program , We will understand easily that 'how it has to be written' . There are certain rule to write C programs . These are :
(a) Each instructions in a C program is written as a separate statement .
(b) The Statements in a program must appear in the same order in which we wish them to be executed .
(c) Blank space may be inserted between two words to improve the readability of the statement .
(d) All statements should be in lower case letters .
(e) Every C statement must end with a semicolon ( ; ) , thus acts as statement terminator .
How to write comment in C program ?
Comments are used in a C program to clarify either the purpose of the program or the purpose of some statement in the program .
comment should be enclosed within /* */ in C . within /* */ , compiler does not take as instruction .
Also comments are written as within //
Example : /* these are comments */ or // these are comments
What is main( ) in C ?
main( ) is a very important part of any C program . main( ) is one type of function . A function is nothing but a container of set of statements . In C program , there are multiple functions . In this discussion , we only talk about main( ) . All the statements that belongs to main( ) are enclosed with a pair of second braces { } .
Function in C also return a value . main( ) function also return an integer value , hence there is an int before main( ) . If for any reason the statements in main( ) fail to do their intended work , then , the function returns a non zero number , which indicates , the program is wrong .
The arithmetic operators available in C are + , - , * , / .
Purpose of printf( ) in C :
printf( ) is a ready made library function to show all the output on the screen . Once we instruct the device through the program ,it needs to displayed on the screen . with the help of this function ,we can easily handle output in C .
To use this ready made function , it is necessary to use #include<stdio.h> at the starting of the program . We will discuss about this in later .
The general form of printf( ) function is ,
printf("format string", list of variables);
format string can contain ,
%f for print real values .
%d for print integer values .
%c for print character values .
'\n' use for takes new lines .
Compilation and Execution in C :
Once you have written the program , you need to type it and instruct the machine to execute it . Two
other tools are needed this , one is Editor & another one is compiler . Compiler convert our program in to machine language program .
Receiving input in C :
In the first program , we assume the values of P and Q . Every time we run the program , we could get the same value for multiplication of two number . If we want to multiply for some other values , then we have require to change the whole program .
To make the program general , we have another function to achieve the program , which is scanf( ) .
this function is a counter part of printf( ) .printf( ) outputs the values to the screen whereas scanf( )
receives them from key board .
Lets try same example as we done at the first ,
#include<stdio.h>
int main()
{
int P;
float Q,R;
printf("Enter the values of P = ");
scanf("%d",&P);
printf("Enter the values of Q = ");
scanf("%f",&Q);
R=P*Q;
printf(" Multiplication of integer and floating number = %f\n",R);
return 0;
}
Note that use of & before the variables in the scanf( ) function is a must . & is 'Address of ' operator .
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Programming
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