Decimal – Simple Definition
A decimal number is a number written using the base-10 system.
Decimal Numbers – Basic Idea
To break a decimal number (example: 2345) into digits:
- no % 10 → gets the last digit
- no // 10 → removes the last digit
This is the main logic used in all programs
SUM OF DIGITS
What does it do?
It adds all the digits in a number
Example:
2345 → 2 + 3 + 4 + 5 = 14
Loop Method
We use a while loop to add digits one by one
SUM OF DIGITS IN LOOP :
no=2345
sum=0
while no>0:
sum=sum+no%10
no=no//10
print(sum)
OUTPUT :
14
Recursion Method
The function calls itself again and again to repeat the process
SUM OF DIGITS IN RECURSION :
def sum1(no,sum):
if no>0:
sum=sum+no%10
no=no//10
return sum1(no,sum)
return sum
print(sum1(1234,0))
OUTPUT :
10
COUNT OF DIGIT
What does it do?
It counts how many digits are in a number
Example:
2345 → 4 digits
Loop Method
In each step, we do count += 1
COUNT OF DIGITS IN LOOP :
no=2345
count=0
while no>0:
count+=1
no=no//10
print(count)
OUTPUT :
4
COUNT OF DIGITS IN RECURSION :
Recursion Method
Idea:
count = 1 + count of remaining digits
def sum1(no,count):
if no>0:
count+=1
no=no//10
return sum1(no,count)
return count
print(sum1(123437,0))
OUTPUT :
6
NUMBER REVERSE
What does it do?
It reverses the number
Example:
2345 → 5432
Loop Method
reverse = reverse * 10 + last digit
NUMBER REVERSE IN LOOP :
no=2345
reverse=0
while no>0:
reverse=reverse*10+no%10
no=no//10
print(reverse)
OUTPUT :
5432
NUMBER REVERSE IN RECURSION :
Recursion Method
Idea:
Take the last digit and build a new number step by step
def sum1(no,reverse):
if no>0:
reverse=reverse*10+no%10
no=no//10
return sum1(no,reverse)
return reverse
print(sum1(123437,0))
OUTPUT :
734321