How to convert char to int in c?

Converting Char to Int in C: A Step-by-Step Guide

Introduction

In C programming, converting a character to an integer is a common task that can be achieved using various methods. This article will provide a comprehensive guide on how to convert a character to an integer in C, including the use of built-in functions, manual conversions, and examples.

Method 1: Using Built-in Functions

C provides several built-in functions to convert a character to an integer. Here are a few examples:

• int c = 'A'; This line of code converts the character ‘A’ to an integer A.
• int c = 'a'; This line of code converts the character ‘a’ to an integer a.
• int c = '0'; This line of code converts the character ‘0’ to an integer 0.

Method 2: Manual Conversion

You can also convert a character to an integer manually using the following steps:

• Step 1: Get the ASCII value of the character.
• Step 2: Convert the ASCII value to an integer using the int data type.

Here’s an example of manual conversion:

#include <stdio.h>



int main() {

    char c = 'A';

    int int_c = (int)c;

    printf("The ASCII value of '%c' is %dn", c, int_c);

    return 0;

}

Method 3: Using the atoi Function

The atoi function is a built-in function in C that converts a string to an integer. Here’s an example of how to use it:

#include <stdio.h>

#include <stdlib.h>



int main() {

    char c = 'A';

    int int_c = atoi(&c);

    printf("The integer value of '%c' is %dn", c, int_c);

    return 0;

}

Method 4: Using the strtol Function

The strtol function is a variant of the atoi function that can handle negative numbers and decimal points. Here’s an example of how to use it:

#include <stdio.h>

#include <stdlib.h>



int main() {

    char c = 'A';

    int int_c = strtol(&c, NULL, 10);

    printf("The integer value of '%c' is %dn", c, int_c);

    return 0;

}

Method 5: Using a Loop

You can also convert a character to an integer using a loop:

#include <stdio.h>



int main() {

    char c = 'A';

    int int_c = 0;

    while (c != '') {

        int_c = int_c * 10 + (c - 'A' + 1);

        c = getchar();

    }

    printf("The integer value of '%c' is %dn", c, int_c);

    return 0;

}

Method 6: Using a Struct

You can also convert a character to an integer using a struct:

#include <stdio.h>



typedef struct {

    char c;

    int int_c;

} char_int;



int main() {

    char_int c;

    c.c = 'A';

    c.int_c = (int)c.c;

    printf("The integer value of '%c' is %dn", c.c, c.int_c);

    return 0;

}

Conclusion

Converting a character to an integer in C is a straightforward process that can be achieved using various methods. The built-in functions int c = 'A'; and int c = 'a'; are simple and efficient ways to convert a character to an integer. Manual conversion using the atoi function is another option, and the strtol function can handle negative numbers and decimal points. The char_int struct is a more complex approach, but it can be useful when working with large numbers or when you need to perform arithmetic operations on integers and characters.

Table: Built-in Functions for Converting Char to Int

Function	Description
int c = 'A';	Converts a character ‘A’ to an integer A
int c = 'a';	Converts a character ‘a’ to an integer a
int c = '0';	Converts a character ‘0’ to an integer 0
atoi(&c)	Converts a string to an integer using the atoi function
strtol(&c, NULL, 10)	Converts a string to an integer using the strtol function
char_int c;	Converts a character to an integer using a struct char_int

Note: The char_int struct is not a standard C struct, and it’s not recommended to use it in production code. It’s mainly used for educational purposes or when working with specific requirements.