C Program to input and print an integer with zero padding.

Think of a number and desire that it must always have a particular number of digits showing. This program works like a help that makes sure your number looks as it is. Just tell it your number and how many digits long you want it to be. If your number is short, the program just enters leading zeros until it straightens it out. This is nice when you want a whole row of numbers to line up perfectly, like with a game score or time display.

#include <stdio.h>
int main() {
int numberFromUser; // This will hold the number you type.
int desiredLength; // This will hold how many digits you want in total.

// First, the program will ask you to enter a whole number.
printf("Please type in a whole number and press Enter: ");
scanf("%d", &numberFromUser);

// Next, the program will ask you for the total length you want the number to have.
// For example, if you type 4, and your number is 12, it will be shown as 0012.

printf("Now, tell me the total number of digits you want the number to have (e.g., 4): ");
scanf("%d", &desiredLength);

// Finally, the program will print your number, adding zeros at the front if needed
// to reach the desired length. The '%0*d' part is what does this:
// - '%' signals a special formatting instruction.
// - '0' tells the program to fill any extra space with zeros.
// - '*' is a placeholder that gets replaced by the 'desiredLength' you entered.
// - 'd' indicates that we are printing a whole number (an integer).

printf("Here's your number with leading zeros: %0*d\n", desiredLength, numberFromUser);
return 0; // This means the program finished successfully.
}

Program Description:
Step by Step Execution with Description and Output:

Step 1: The Program Starts
The program comes alive. By now, nothing appears on the screen.

Step 2: Asking for Input
printf("Please type in a whole number and press Enter: ");
causes the above text to appear on your screen:
Please type in a whole number and press Enter:
The program is now waiting for you to type a number.

Step 3: User Input
You enter the number 12 and press Enter.

Step 4: Reading the Input
scanf("%d", &numberFromUser);
takes the command 12 that you entered and saves it into the memory of the program.

Step 5: Asking for Desired Length
printf("Now, tell me the total number of digits you want the number to have (e.g., 4): ");
displays the next text on your screen:
Now, tell me the total number of digits you want the number to have (e.g., 4):
The program is now waiting for your next input.

Step 6: User Input for Length
You type in the number 5 and press Enter.

Step 7: Reading Desired Length
The line:
scanf("%d", &desiredLength);
takes the 5 you typed and stores it in the program's memory.

Step 8: Formatting and Printing the Output
printf("Here's your number with leading zeros: %0*d\n", desiredLength, numberFromUser);
does like this:
"Here's your number with leading zeros: " - This text is being printed on the screen.
%0*d - This is the formatting instruction. It tells the program to take the numberFromUser (which is 12) and print it as a whole number (d). The 0 means to add leading zeros if needed, and the * means the total width should be taken from the desiredLength (which is 5).
\n - This adds a newline at the end, moving the cursor to the next line.

Step 9: Output on Your Screen
According to the format, the number 12 will be forwarded with three leading zeros, hence making a total of five digits. The complete output that you will see is:
Here's your number with leading zeros: 00012

Step 10: Ending of Program
return 0;
indicates the end of execution of the program without any errors. The program closes, and you return to your terminal or command prompt.

Practice/Assignment set 2:
1. C program to find sum of the square of all natural numbers from 1 to N.
Series: 1^2+2^2+3^2+4^2+..N^2
2. C program to find sum of the all natural numbers from 1 to N.
Series: 1+2+3+4+..N
3.C program to find the sum of Natural Number/Factorial of Number of all natural numbers from 1 to N.
Series: 1/1! + 2/2! + 3/3! + 4/4! + ... N/N!
4) C program to find sum of following series:
1+ 1/2 + 1/3 + 1/4 + 1/5 + .. 1/N
5) C program to find sum of following series:
1 + 3^2/3^3 + 5^2/5^3 + 7^2/7^3 + ... till N terms

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