The document discusses a 4-bit binary coded decimal (BCD) adder. A BCD adder can add two 4-bit BCD numbers and produce a 4-bit BCD sum. If the sum exceeds 9 in decimal, a carry is generated. The document also mentions full adders, 7-segment displays, and 74LS47 BCD to 7-segment decoder/driver ICs. It provides an explanation of why 6 is added to BCD sums that exceed 9.

2. 
BCD adder A 4-bit binary adder that is capable of
adding two 4-bit words having a BCD (binary-coded
decimal) format. The result of the addition is a BCD-
format 4-bit output word, representing the decimal sum
of the addend and augends, and a carry that is
generated if this sum exceeds a decimal value of 9.
DEFINITION

3. 
 WIRES
 PUSH PULL SWITCHES
 RESISITORS
EQUIPMENTS

4. 
AND GATE FULL ADDER
OR GATE BATTERY
7 SEGMENT

5. 
74LS47 datasheet
 74LS47 is a BCD to 7-segment
decoder/driver IC. It accepts a binary
coded decimal as input and converts it
into a pattern to drive a seven-segment
for displaying digits 0 to 9.

6. 
7 segment display
 A typical 7-segment LED display component, with
decimal point. A seven-segment display (SSD), or seven-
segment indicator, is a form of electronic display device
for displaying decimal numerals that is an alternative to
the more complex dot matrix displays

7. 
 Full adder accepts three three
binary inputs(A,B and Carry-
in)and provide two binary
outputs(Sum and Carry)
FULL ADDER.

8. 
4-bit bcd adder
4-bit Adder
4-bit Adder
0 0
s3 s2 s1 s0
S3 S2 S1 S0
Cin
K
0 1 1 00 1 1 1
1 1 0 1
0
1 1 0 1
1 1
1
0 0 1 1
1
0
1

9. 
TRUTH TABLE

10. 
Why add 6 to the result?
 Sum of two BCD digits exceeding 9.
 A carry is generated.
 Converting the invalid digit into valid digit.
 Carry generated by adding 6 to the invalid BCD
digit’s passed on to the next BCD digit.