Example: Binary to Decimal to Hexadecimal Converter in C

// Binary to Decimal to Hexadecimal Converter
    #include <stdio.h>
    #include <string.h>
    #include <math.h> // For pow function, though direct multiplication is often better for performance
    #include <stdlib.h> // For itoa if available, or custom implementation

    // Function to convert binary string to decimal long long
    long long binaryToDecimal(const char *binaryString) {
        long long decimal = 0;
        int power = 0;
        int length = strlen(binaryString);

        for (int i = length - 1; i >= 0; i--) {
            if (binaryString[i] == '1') {
                decimal += (long long)pow(2, power);
            } else if (binaryString[i] != '0') {
                printf("Error: Invalid binary digit '%c'\n", binaryString[i]);
                return -1; // Indicate an error
            }
            power++;
        }
        return decimal;
    }

    // Function to convert decimal long long to hexadecimal string
    void decimalToHexadecimal(long long decimalNum, char *hexadecimalString) {
        if (decimalNum == 0) {
            strcpy(hexadecimalString, "0");
            return;
        }

        char hexChars[] = "0123456789ABCDEF";
        int i = 0;
        char tempHex[100]; // Temporary buffer for reverse order

        while (decimalNum > 0) {
            tempHex[i++] = hexChars[decimalNum % 16];
            decimalNum /= 16;
        }
        tempHex[i] = '\0';

        // Reverse the temporary string to get the correct hexadecimal order
        int start = 0;
        int end = i - 1;
        while (start < end) {
            char temp = tempHex[start];
            tempHex[start] = tempHex[end];
            tempHex[end] = temp;
            start++;
            end--;
        }
        strcpy(hexadecimalString, tempHex);
    }

    int main() {
        char binaryInput[100];
        char hexadecimalOutput[100];

        printf("Enter a binary number: ");
        scanf("%s", binaryInput);

        long long decimalResult = binaryToDecimal(binaryInput);

        if (decimalResult != -1) { // Check for valid binary input
            decimalToHexadecimal(decimalResult, hexadecimalOutput);
            printf("Binary: %s\n", binaryInput);
            printf("Decimal: %lld\n", decimalResult);
            printf("Hexadecimal: %s\n", hexadecimalOutput);
        }

        return 0;
    }