C Exercises: Convert a string to an unsigned long integer

Last update on July 29 2025 12:55:07 (UTC/GMT +8 hours)

2. String to Unsigned Long Conversion

Write a C program to convert a string to an unsigned long integer.

Sample Solution:

C Code:

#include<stdio.h>
#include<stdlib.h>

int main ()
{
char buffer[123]; // Define a character array 'buffer' to store user input
unsigned long ul; // Define an unsigned long variable 'ul' to store the converted value

    // Print a message asking the user for input
printf ("\nInput an unsigned number: ");

    // Read user input from standard input and store it in 'buffer'
fgets (buffer,123,stdin);

    // Convert the string in 'buffer' to an unsigned long, using base 0 (auto-detect)
ul = strtoul (buffer,NULL,0);

    // Print the converted value
printf ("Output: %lu\n\n",ul);

return 0; // Indicate successful program execution
}

Sample Output:

Input an unsigned number: 25                                                                                  
Output: 25

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to convert a hexadecimal string to an unsigned long integer using strtoul() with error checking.
Write a C program to parse a string with embedded whitespace into an unsigned long integer and handle invalid input.
Write a C program to convert a string with a leading '+' sign into an unsigned long integer and detect overflow conditions.
Write a C program to convert a string to an unsigned long integer and verify that the entire string represents a valid number.

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