convert a number character to an int in C

Answered on: Wednesday 24 January, 2024 / Duration: 13 min read

Programming Language: C , Popularity :7/10

Solution 1:

Certainly! In C, you can convert a character representing a number to an integer using the atoi function from the stdlib.h library. Here's a simple code example:

c
#include <stdio.h>
#include <stdlib.h>
int main() {
 // Character representing a number
 char charNumber = '5';
 // Using atoi to convert character to integer
 int convertedNumber = atoi(&charNumber);
 // Displaying the result
 printf("Character: %c\n", charNumber);
 printf("Converted to integer: %d\n", convertedNumber);
 return 0;
}

In this example, the atoi function is used to convert the character charNumber to an integer convertedNumber. The result is then printed to the console. When you run this program, you should see output like:


Character: 5
Converted to integer: 5

Make sure to include the necessary header files (stdio.h and stdlib.h) at the beginning of your program.

Solution 2:

Converting a Number Character to an Int in C

In C, you can convert a number character to an int using the atoi() function. This function takes a string as its input and returns the integer value of the first number in the string. If the string does not contain a number, atoi() returns 0.

The following code shows how to use atoi() to convert a number character to an int:

c
#include <stdio.h>
#include <stdlib.h>
int main() {
 // Define a number character.
 char ch = '5';
 // Convert the number character to an int.
 int num = atoi(&ch);
 // Print the integer value of the number character.
 printf("The integer value of the number character '%c' is %d.\n", ch, num);
 return 0;
}

When this code is run, the following output is produced:


The integer value of the number character '5' is 5.

Example 2: Converting a String of Numbers to an Int

You can also use atoi() to convert a string of numbers to an int. To do this, simply pass the string to the atoi() function.

The following code shows how to use atoi() to convert a string of numbers to an int:

c
#include <stdio.h>
#include <stdlib.h>
int main() {
 // Define a string of numbers.
 char str[] = "12345";
 // Convert the string of numbers to an int.
 int num = atoi(str);
 // Print the integer value of the string of numbers.
 printf("The integer value of the string of numbers '%s' is %d.\n", str, num);
 return 0;
}

When this code is run, the following output is produced:


The integer value of the string of numbers '12345' is 12345.

Note: The atoi() function is not case-sensitive, so it will convert both upper-case and lower-case letters to numbers. For example, the following code will also produce the output 12345:

c
#include <stdio.h>
#include <stdlib.h>
int main() {
 // Define a string of numbers.
 char str[] = "12345";
 // Convert the string of numbers to an int.
 int num = atoi(str);
 // Print the integer value of the string of numbers.
 printf("The integer value of the string of numbers '%s' is %d.\n", str, num);
 return 0;
}

Conclusion

The atoi() function is a simple and efficient way to convert a number character or a string of numbers to an int in C. It is a useful function to know for any programmer who works with numbers in C.

Solution 3:

In C, you can convert a character to an integer using the int type and the (int) cast operator. In C, characters are represented as integers, where each character corresponds to a unique integer value according to the ASCII standard. For example, the character '0' has an integer value of 48, '1' has a value of 49, and so on.

To convert a character to an integer, you can simply assign the character to an int variable or cast it to int using the (int) operator. Here's an example:

c
#include <stdio.h>
int main() {
 char c = '5';
 int i = (int)c;
 printf("Character: %c\n", c);
 printf("Integer: %d\n", i);
 return 0;
}

Output:

makefile
Character: 5
Integer: 53

In this example, the character '5' is assigned to the char variable c. The integer value of c is then obtained by casting it to int using the (int) operator and assigning it to the int variable i. Finally, the character and integer values are printed using printf.

Note that the integer value of '5' is 53, not 5, because '5' is the ASCII code for the character '5', which is different from its numerical value. If you want to convert a digit character to its numerical value, you can subtract the ASCII code of '0' from its integer value, like this:

c
#include <stdio.h>
int main() {
 char c = '5';
 int i = (int)c - (int)'0';
 printf("Character: %c\n", c);
 printf("Integer: %d\n", i);
 return 0;
}

Output:

makefile
Character: 5
Integer: 5

In this example, the integer value of '5' is obtained by subtracting the ASCII code of '0' from its integer value,