How do you write a C Program to Find the First Digit Of a Number with an example?
C Program to Find First Digit Of a Number
This program will allow the user to enter any number. And then, it is going to find the First Digit of the user entered value.
#include <stdio.h> #include <math.h> int main() { int Number, FirstDigit, Count; printf("\n Please Enter any Number that you wish : "); scanf("%d", & Number); Count = log10(Number); FirstDigit = Number / pow(10, Count); printf(" \n Total Number of Digit in a Given Number %d = %d", Number, Count); printf(" \n The First Digit of a Given Number %d = %d", Number, FirstDigit); return 0; }

Within this Program to Find the First Digit, the User entered Value: Number = 1234
Count = log10(Number) – This will return the total number of digits in a number -1
Count = 3
FirstDigit = 1234 / pow(10, 3) = 1234 / 1000 = 1.234 = 1
C Program to return First Digit Of a Number
This program will use the While Loop to find the First Digit of the user entered value.
#include <stdio.h> int main() { int Number, FirstDigit; printf("\n Please Enter any Number that you wish : "); scanf("%d", & Number); FirstDigit = Number; while(FirstDigit >= 10) { FirstDigit = FirstDigit / 10; } printf(" \n The First Digit of a Given Number %d = %d", Number, FirstDigit); return 0; }
Please Enter any Number that you wish : 354
The First Digit of a Given Number 354 = 3
Within this Program to Find the First Digit Of a Number, Number = 354
While Loop First Iteration while (354 >= 10)
FirstDigit = FirstDigit / 10 = 354 / 10 = 35
While Loop Second Iteration while (35 >= 10)
FirstDigit = FirstDigit / 10 = 35 / 10 = 3
While Loop Third Iteration while (3 >= 10)
Condition is False, so the C Programming compiler will exit from the While Loop and print 3 as output.
Using Function
This C program to display the First Digit Of a Number is the same as above. However, this time, we divided the code using the Functions concept.
#include <stdio.h> #include <math.h> int First_Digit(int num); int main() { int Number, FirstDigit; printf("\n Please Enter any Number that you wish : "); scanf("%d", & Number); FirstDigit = First_Digit(Number); printf(" \n The First Digit of a Given Number %d = %d", Number, FirstDigit); return 0; } int First_Digit(int num) { while(num >= 10) { num = num / 10; } return num; }
Please Enter any Number that you wish : 657489
The First Digit of a Given Number 657489 = 6