Short Question & Answers 

Q40: Explain Combinational Function Devices? 
Digital circuits are formed by the combination of Logic Gates. Xor, Xnor, NAND, NOR are combinational function devices. 
Q41: Differentiate between hexadecimal and octal number system. 
Octa decimal use Base 8 whereas Hexa decimal use Base 16. 
Q42: One of the ABEL entry methods uses logic equation. Explain at least two examples? 
ABEL however is case sensitive, thus variable „A‟ is treated separately from variable „a‟. All ABEL equations must end with „;‟. Examples: X = AB(bar)C + (ABC)bar + AB + B(bar)C Y = (A(bar)+B+C(bar)+D)(A+B+C)
Solutions: X = A& !B & C # !A & !B & !C # A & B # !B & C;
Y = (!A # B # !C #D) & (A # B # C); 
Q43: Draw function table of a half adder circuit? 

Q44: Draw the function table of 2to4 decoder. 

Q45: Explain 8input Multiplexer with the help of circuit Diagram and Function Table. 

Q46: Half adder explanation its function table Boolean expression and circuit diagram. 
HalfAdder: A HalfAdder can be fully described in terms of its Function table, its Sum and Carry Out Boolean Expressions and the circuit Implementation.
HalfAdder Function Table: The HalfAdder has a 2bit input and a 2bit output. The function table of the HalfAdder has two input columns representing the two single bit numbers A and B. The function table also has two output columns representing the Sum bit and Carry Out bit.
HalfAdder Sum & Carry Out Boolean Expressions: The Sum and Carry Out expressions of the HalfAdder can be determined from the function table. The HalfAdder Sum and Carry Out outputs are defined by the expressions

Q47: Explain TriState Buffers with the help of block diagram. 
TriState Buffer is a NOT gate with a control line that disconnects the output from the input. When the control line is high the buffer operates like a NOT gate and when the control line is low the output is disconnected from the output and high impedance is seen at the output. Tristate buffers are used to disconnect the outputs of devices which are connected or share a common output line.

