C Program to convert a decimal number to a hexadecimal number

The following is a C program to convert a decimal number to a binary number:

Expected Output:

1st run:

2nd run:

How it works

To convert a decimal number to a hexadecimal number, we follow these steps:

Step 1: Divide the decimal number continuously by 16 and write the remainder on the right-hand side of the dividend. We repeat this process until we get the quotient 0.

Step 2: If the remainder is greater than 10, then replace it with a hexadecimal character given in the table below:

Decimal Hexadecimal
10 A
11 B
12 C
13 D
14 E
15 F

Step 3: Write the remainders from bottom to top.

Let’s take some examples:

Example 1: Convert decimal 210 to hexadecimal number.

Step 1:

Quotient Remainder
210/16 13 2
13/16 0 13

Step 2:

Quotient Remainder Hexadecimal
210/16 13 2 2
13/16 0 13 D

Step 3:

21010 = 0xD216

Example 2: Convert decimal 100 to a hexadecimal number.

Step 1: 

Quotient Remainder
100/16 6 4
6/16 0 6

Step 2:

In this case, both the remainders are smaller than 10, so we don’t need to replace them with the hexadecimal characters.

Step 3:

10010 = 0x6416

The following table shows what happens at each iteration of the loop (assuming num = 198):

Iteration rem hex_arr num i
After 1st iteration rem=198%16=6 hex_arr[0]=48+6=54 num=198/16=12 i=1
After 2nd iteration rem=12%16=12 hex_arr[1]=55+12=67 num=12/16=0 i=2

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