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How to convert a string to hexadecimal in C

Converting a character array or any string to its respective hexadecimal form is simple. The only thing we have to do is to follow the below steps.

  1. Take each character from the string and convert it into its respective ASCII value in order to get the integer, i.e., Decimal value.
  2. Next, convert that decimal or ASCII value to Hexadecimal.

Steps to be followed to convert a decimal value to hexadecimal value:

  • The decimal number is divided by 16. Consider the division to be an integer division.
  • Make a note of the remainder (in hexadecimal).
  • Divide the output(quotient) once again by 16. Consider the division to be an integer division.
  • The remainders' digit order from last to first determines the hex value.
  • We repeat the above process until the quotient becomes zero when divided by 16.

Note: The Base of 16 system is used in the "Hexadecimal" or simply "Hex" numbering system. Hexadecimal numbers are represented by 16 symbols: 0, 1, 2, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F. Here, (A, B, C, D, E, and F) stand for (10, 11, 12, 13, 14, 15).

For example, consider a character as 'k'; now, let's follow the above steps to get our result.

Initially, we find its respective ASCII value, k's ASCII value, is 107.

107 is a decimal number that must be converted to its hexadecimal form. For converting, we follow the above steps:

Firstly, we modulo divide 107 by 16 to get the remainder.

  1. 107%16=11 (remainder)
    Then 107/16=6
  2. 6%16=6 (remainder)
    And 6/16=0 as the quotient is zero, stop the process.

Hexadecimal= 611; since 11 is represented as 'B' in hexadecimal values, we replace 11 with 'B'.

The resultant Hexadecimal value is 6B.

Therefore, k is represented ad 6B in hexadecimal form.

Now, we can implement the program with the help of the above logic.

Program to convert string to Hexadecimal:

Example 1:

#include <stdio.h>
#include <string.h>
int main()
    unsigned char str[100], strH[200];
    int i, j;
    printf("Enter the string: ");
    scanf("%[^\n]s", str);
    printf("\nString you entered is: %s\n", str);
    memset(strH, 0, sizeof(strH));
    for (i = 0, j = 0; i < strlen(str); i++, j += 2) {
        sprintf((char*)strH + j, "%02X", str[i]);
    strH[j] = '\0';

printf("Hexadecimal conversion of the given string is: ");
    printf("%s\n", strH);
return 0;


How to convert a string to hexadecimal in c

Example 2:

#include <stdio.h>
#include <string.h>
char *decToHexa(int n)
	char hexaDeciNum[100];
	int i = 0;
	while (n != 0) 
		int temp = 0;
		temp = n % 16;

		if (temp < 10) {
			hexaDeciNum[i] = temp + 48;
		else {
			hexaDeciNum[i] = temp + 55;

		n = n / 16;

	char ans[100] ="";

	for (int j = i - 1; j >= 0; j--)
	    char add[100]={hexaDeciNum[j]};

	return ans;
int main()

char hex[100] ="";
char string[10];
printf("Enter the string:");
	for (int i=0;i<strlen(string);i++) 
		char ch=string[i];
		int tmp =(int)ch;
	printf("The Hexadecimal form is %s",hex);
	return 0;


How to convert a string to hexadecimal in c

Therefore, we have seen two programs for the implementation of the above problem. Although two programs produce the same output and are used for the same cause, the way they produce the output is completely different from each other.

The fundamental benefit of using hexadecimal numbers is that they require less memory to hold more numbers; for instance, they can store 256 numbers in two digits, as opposed to 100 for decimal numbers. Computer memory addresses are also represented by this numeric format. Any binary digit may be represented using only 4 bits, and converting between Hexadecimal and binary is simple. Input and output are simpler to manage in hexadecimal format.

The fields of data science, artificial intelligence, and machine learning all have many benefits. It is also used in colour references, Assembly language programs, Error messages and Media Access Control (MAC) addresses. Also, it can be used to represent numbers kept in a CPU's registers or in main memory, as well as during the debugging phase of programming.

Hexadecimal's main drawback is that it can be challenging for individuals to read and write, and doing operations like multiplications and divisions with it can be challenging. Also, the most challenging number system for working with computer data is hexadecimal.