Summation of first n digit of even numbers
Summation of first n digit of even numbers (Using Formula) - C programming example
In this code a number n will be given as input. The C program example will tell us the summation of that first n digit of even numbers.
C program code 1
#include<stdio.h>
#include<conio.h>
main()
{
int n,sum;
printf("please input the amount of even numbers you want to add up \n");
scanf("%d",&n);
sum=n*(n+1);
printf("the answer is %d",sum);
getch();
}
Output of the code
 |
| Summation of first n digit of even numbers |
Explanation of the C program code
#include<stdio.h>
#include<conio.h>
· This are called header file. A header file is a file with extension .h which contains c function declarations and macro definitions to be shared between several source files. The c programming language provides many standard library functions for file input and output. These functions make up the bulk of the c standard library header <stdio.h>. On the other hand <conio.h>is a c header file used mostly by MS-DOS compilers to provide console input/output. It is not part of the C standard library or ISO C. This header declares several useful library functions for performing “console input and output” form a program.
Main()
· In C programming, program execution starts from the main() function. The main function can in-turn call other functions. When main calls a function, it passes the execution control to the function. The function returns control to main when a return statement is executed or when end of function is reached.
int n,sum;
· Int is a variable or data type. A variable declared to be of type int (integer) can be used for storing integer numbers. Here we declare “n” and “sum” variable in int type.
Printf() function
· C uses printf() function to write from the input devices. This function has been declared in the header file called stdio.h .Any text written within the pair of quotes (“”) is displayed as such by printf() function on the screen.
Scanf() function
· This function is used to get input from the user of the program. Scanf(“%d”,&n) is used here. So, this program will read in an integer value of “n” valuable that the user enters on the keyboard (%d is for the integer values. As there is “&n”, the number user enters will be the value of “n” valuable.
Printf(“the sum is %d”,sum)
· The integer “sum” is printed on the screen by this line. Here %d represents the integer value of “sum”.
Getch()
· Getch() is added in order to stop the program. It is used in order to stop the program while the header file <conio.h> is used.
C program code 2
#include<stdio.h>
#include<conio.h>
main()
{
int sum,n,i;
printf("Enter the amount of number you want to sum up: \n");
scanf("%d",&n);
sum=0;
#include<conio.h>
main()
{
int sum,n,i;
printf("Enter the amount of number you want to sum up: \n");
scanf("%d",&n);
sum=0;
for(i=1;i<=n;i++)
{
sum=sum+i;}
printf("The sum of first %d digit even number is %d",n,sum);
getch();
}
Explanation of the code
· #include<stdio.h>
#include<conio.h>
Ø This
are called header file. A header file is a file
with extension .h which contains C function declarations and
macro definitions to be shared between several source files The C programming
language provides many standard library functions for file
input and output. These functions make up the bulk of
the C standard library header
<stdio.h>.In the other hand <conio.h> is a C header
file used mostly by MS-DOS compilers to provide console input/output. It is not
part of the C standard library or ISO C. This header declares several useful
library functions for performing "console input and output" from a
program.
· main()
Ø In
C, program execution starts from the main() function. The main
function can in-turn call other functions. When main calls
a function, it passes the execution control to that function.
The function returns control to main when a
return statement is executed or when end of function is
reached.
· int sum,n,,i;;
Ø int
is a variable or data type. A variable declared
to be of type int can be used for storing integer
numbers (values which doesn’t contain decimal places). Here we declare “sum”, “n”, and “i” as int type. So this variables can take only integer values.
· printf() function
Ø C
uses printf() function to write from the input devices. This function
has been declared in the header file called stdio.h
. Any text written within the pair of quotes ("") is displayed
as such by printf() function on the screen.
· scanf() function
Ø This
function is used to get input from the user of the program. scanf(“%d”,&n”) is used here. So, this program will read in a integer
value for “n” variable that the user enters on the keyboard (%d is
for integer values. As there is “&n”, the number user enters will be
the value of “n” variable).
· For loop
A for-loop (or simply for loop)
is a control flow statement for specifying iteration, which
allows code to be executed repeatedly. The initialization
statement is executed only once. Then,
the test expression is evaluated. If the test expression is false, for loop is
terminated. But if the test expression is true, codes inside the body
of for loop is executed and the update expression is updated. This
process repeats until the test expression is false. The for loop is
commonly used when the number of iterations is known. In this for loop, the loop will start when
i=1. If i is less than or equals to the
entered number n, the statement in the loop will be executed. After executing
once, i will increase one. When i is more than n, the loop will end.
· getch() function
Ø getch() is
used to hold the console(output) window on the screen after the whole program
run is completed till the user enters a key from keyboard. This function is
present in the header file called conio.h.
Final result
This program will show us the summation of the first n even numbers. What we need to is just input the number of even numbers we want to add up.
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