C Exercises: Convert a string to a long integer

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

3. String to Long Conversion

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

Sample Solution:

C Code:

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

int main ()
{
    // Define a character array 'buffer' containing a string of numbers in different bases
char buffer[] = "2016 40a0b0 -1101110100110111100110 0x5abfff";

    // Define pointers for strtol function to update
char * ptr_end;

    // Define four variables to store converted values
long int i1, i2, i3, i4;

    // Convert the first section of 'buffer' to a long integer in base 10
    i1 = strtol (buffer, &ptr_end, 10);

    // Convert the second section of 'buffer' to a long integer in base 16 (hexadecimal)
    i2 = strtol (ptr_end, &ptr_end, 16);

    // Convert the third section of 'buffer' to a long integer in base 2 (binary)
    i3 = strtol (ptr_end, &ptr_end, 2);

    // Convert the fourth section of 'buffer' to a long integer in the appropriate base (auto-detect)
    i4 = strtol (ptr_end, NULL, 0);

    // Print the converted values in decimal format
printf ("\nIn decimals: %ld, %ld, %ld, %ld.\n\n", i1, i2, i3, i4);

return 0;
}

Sample Output:

In decimals: 2016, 4235440, -3624422, 5947391.

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to convert a string representing a signed number to a long integer, handling extra whitespace.
Write a C program to convert a string with a '+' or '-' sign to a long integer using strtol() and implement error detection.
Write a C program to convert a locale-specific numeric string to a long integer and account for different numeral formats.
Write a C program to convert a string to a long integer and gracefully handle invalid or non-numeric characters.

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