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    Converting an ASCII string or character to an integer in C can be done using the standard library function atoi() or by manual computation. The method you choose depends on whether you are converting a string of digits or a single ASCII character.

    Example using atoi() (ASCII string to integer):

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

    int main() {
    char str[] = "12345";
    int num = atoi(str); // Converts string to integer
    printf("The integer value is: %d\n", num);
    return 0;
    }
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    This will output:

    The integer value is: 12345
    Copied!

    Here, atoi() (ASCII to Integer) reads the numeric characters from the start of the string and converts them into an integer.

    Example for single ASCII digit conversion (character to integer):

    #include <stdio.h>

    int main() {
    char ch = '7';
    int num = ch - '0'; // Converts ASCII digit to its numeric value
    printf("Character '%c' as integer: %d\n", ch, num);
    return 0;
    }
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    This works because in the ASCII table, digits '0' to '9' are stored in consecutive codes (48–57), so subtracting '0' gives the actual numeric value.

    How do I convert a string to an integer without assignment?
    Or just converting without assignment: Use the ASCII to Integer atoi() function which accepts a string and converts it into an integer: If the string contains a decimal, the number will be truncated: "23" is not an ASCII character, so this has no bearing on the (unclear) question.
    stackoverflow.com
    Stack Overflow
    https://stackoverflow.com/questions/5322056
    How to convert an ASCII character into an int in C
  1. GeeksForGeeks
    https://www.geeksforgeeks.org › convert-string-to-int-in-c

    Convert String to int in C - GeeksforGeeks

    Jul 23, 2025 · We can use loops to convert a string to an integer character by character using their ASCII values. Initialize a variable num = 0. Start traversing the string str from the front. For each character …

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  2. Stack Overflow
    https://stackoverflow.com › questions

    How to convert an ASCII character into an int in C

    Mar 16, 2011 · Use the ASCII to Integer atoi() function which accepts a string and converts it into an integer: If the string contains a decimal, the number will be truncated: "23" is not an ASCII character, …

    • Reviews: 2
      Usage example
      int a_as_int = (int)'a';
    • WsCube Tech
      https://www.wscubetech.com › ... › programs › string-to-int

      How to Convert String to Int in C? 4 Ways With Code

      When you want to convert string to integer in C without using atoi function, you can manually implement conversion logic. This custom approach uses loops and ASCII values to convert a numeric string into …

    • Tutorial Kart
      https://www.tutorialkart.com › c-programming › how-to...

      How to Convert a String to an Integer in C - Tutorial Kart

      These functions help parse numerical values from a string representation and store them as an integer type. In this tutorial, we will cover different methods to convert …

    • Delft Stack
      https://www.delftstack.com › howto › c-string-to-int

      How to Convert a String to Integer in C - Delft Stack

      Feb 2, 2024 · In C programming, converting a string to an integer is a common operation, and there are several methods available to accomplish this task. Three …

    • Includehelp.com
      https://www.includehelp.com › c-programs › c-program...

      C program to convert ascii to integer (atoi () implementation)

      Here, we are going to learn how to convert ascii to integer (atoi () implementation) in C programming language?

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    • digibeatrix.com
      https://www.digibeatrix.com › en › standard-library...

      Understanding atoi () in C: How to Convert Strings to …

      atoi (ASCII to Integer) is a function provided by the C standard library that converts a string into an integer. It’s typically used as shown below: int num = atoi("12345"); …

    • thinkage.ca
      https://www.thinkage.ca › gcos › expl › lib › atoi.html

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      "atoi" converts the string pointed to by "s" into an integer. The string may consist of any number of blanks and/or tabs, possibly followed by a sign, followed by a string of digits.

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      How to convert a string to a integer in C - Online Tutorials Library

      Converting strings to integers in C can be done using atoi () for simple cases or strtol () for better error handling. Choose the method based on your specific requirements for error checking and validation.

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      [2 Methods] C Program to Implement atoi() Function

      Apr 6, 2024 · Many times in your project you need to convert this string to a number so that you can perform mathematical calculations. You can convert the string to …

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