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The binary code is the underlying of all computation in logic design. However, decimal numbers are 
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more convenient for human and can easily be shown by 7-segments. To cope with decimal arithmetic, 
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designers usually use special coding mechanism such as Binary Coded Decimal (BCD).
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This lecture explains this coding approach and how to convert a binary number into the equivalent 
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BCD to be shown on 7-segment displays.
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In the BCD coding technique, each decimal digit is shown by a four-bit code.  
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This code contains the binary representation of the digit.
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For example, the binary representation of 24 is 00011000; 
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however, its BCD code is the concatenation of the BCD codes for digits 2 and 4, which are
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their 4-bit binary code. Converting a binary number into the equivalent BCD and then to the 
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7-segment code is the goal of this lecture. 
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A 4-bit BCD can represent a decimal digit. However, there are two ways to save the code: using 4 
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bits (or a nibble) which is called packed BCD or using 8 bits (or a byte) which is called unpacked 
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BCD. In the 8 bits, the upper 4 bits are zero.
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The two different BCD representations of 12 are shown in this figure. Whereas the unpacked 
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BCD requires two bytes, 
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the packed BCD needs only one byte of memory. 
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This table shows the 1-digit packed BCD codes for numbers from 0 to 9. and this one shows
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the 2-digit packed 
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BCD codes for numbers from 10 to 99.
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Designing a digital circuit to convert a binary code into its equivalent BCD would be our next topic.
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In the following lectures, I will explain two different methods to address this problem in HLS.
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These are the takeaway messages.
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BCD coding represents the decimal numbers.
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There are two types of BCD representation: packed and unpacked.
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Now the quiz for this lecture Find the BCD code for the binary number.