C Exercises: Convert a string to an integer

Last update on July 29 2025 12:57:24 (UTC/GMT +8 hours)

13. String to Integer Conversion

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

Sample Solution:

C Code:

#include<stdio.h>      // Include the standard input/output header file.
#include<stdlib.h>     // Include the standard library header file.

int main ()          // Start of the main function.
{
int num1;          // Declare an integer variable 'num1'.
char my_array[256];   // Declare a character array 'my_array' with a maximum size of 256.

printf ("\nInput a number : ");   // Prompt the user to input a number.
fgets (my_array, 256, stdin);     // Read a line of input from the user and store it in 'my_array'.

    num1 = atoi (my_array);   // Convert the string in 'my_array' to an integer and store it in 'num1'.

printf ("The value Input is %d.\n\n", num1);   // Print the value of 'num1'.

return 0;   // Return 0 to indicate successful execution of the program.
}   // End of the main function.

Sample Output:

Input a number : 100                                                                                          
The value Input is 100.

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to convert a numeric string to an integer using both atoi() and manual parsing.
Write a C program to convert a string to an integer while handling non-numeric characters gracefully.
Write a C program to convert a string representing a negative number to an integer and verify the sign.
Write a C program to convert a numeric string to an integer and detect potential overflow conditions.

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