Program to check whether the given number is a valid mobile number or not using functions

Algorithm:

1. Define function is_valid_mobile_number that:
   • Takes a string number as input
   • Checks if length is exactly 10 and all characters are digits
   • Checks if first digit is 7, 8, or 9
   • Returns True if both conditions are met, False otherwise
2. In main program:
   • Get mobile number as input from user
   • Call is_valid_mobile_number function
   • Print appropriate message based on return value

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Pseudocode:

FUNCTION is_valid_mobile_number(number)
    IF length of number = 10 AND number contains only digits THEN
        IF first digit of number IN [7, 8, 9] THEN
            RETURN true
        END IF
    END IF
    RETURN false
END FUNCTION

// Main program
OUTPUT "Enter the mobile number: "
INPUT mobile_number

IF is_valid_mobile_number(mobile_number) THEN
    OUTPUT "The mobile number is valid."
ELSE
    OUTPUT "The mobile number is not valid."
END IF

END

Program:

# Function to check if the given number is a valid mobile number
def is_valid_mobile_number(number):
    # Check if the number contains exactly 10 digits
    if len(number) == 10 and number.isdigit():
        # Check if the first digit is 7, 8, or 9
        if number[0] in ['7', '8', '9']:
            return True
    return False

# Input: Mobile number as a string
mobile_number = input("Enter the mobile number: ")

# Check if the mobile number is valid
if is_valid_mobile_number(mobile_number):
    print("The mobile number is valid.")
else:
    print("The mobile number is not valid.")

Flowchart:

flowchart TD subgraph Function[is_valid_mobile_number Function] A([Start Function]) B[/Input: number/] C{Length = 10 AND\nall digits?} D{First digit is\n7, 8, or 9?} E[Return True] F[Return False] A --> B B --> C C -->|Yes| D C -->|No| F D -->|Yes| E D -->|No| F end subgraph Main[Main Program] M1([Start]) M2[/Input mobile_number/] M3{Call\nis_valid_mobile_number\nfunction} M4[/Print: Number is valid/] M5[/Print: Number is not valid/] M6([End]) M1 --> M2 M2 --> M3 M3 -->|True| M4 M3 -->|False| M5 M4 --> M6 M5 --> M6 end

Important!
If you find any mistakes in my code or flowchart, please comment below this post. I will be happy to correct them and clear up any doubts you may have.

Program to check whether the given number is a valid mobile number or not using functions