1. What are the length of the 8086 's address bus...

 repres"16-bit microprocessor" identity of the 8086.
A 20-bit external address bus provides a 1 MB physical address space (220 = 1,048,576).
How large is the instruction queue of the 8086? 

List the elements of the execution unit,

• Carry flag − This flag indicates an overflow condition for arithmetic operations.

• Auxiliary flag − When an operation is performed at ALU, it results in a carry/barrow from lower nibble (i.e. D0 – D3) to upper nibble (i.e. D4 – D7), then this flag is set, i.e. carry given by D3 bit to D4 is AF flag. The processor uses this flag to perform binary to BCD conversion.

• Parity flag − This flag is used to indicate the parity of the result, i.e. when the lower order 8-bits of the result contains even number of 1’s, then the Parity Flag is set. For odd number of 1’s, the Parity Flag is reset.

• Zero flag − This flag is set to 1 when the result of arithmetic or logical operation is zero else it is set to 0.

• Sign flag − This flag holds the sign of the result, i.e. when the result of the operation is negative, then the sign flag is set to 1 else set to 0.

• Overflow flag − This flag represents the result when the system capacity is exceeded.

 What is the maximum amount of memory that can be active at a given time in the 8086?
in 8086 microprocessor the total memory addressing capability is 1MB
. Which part of the 8086's memory address space can be used to store the instruction of a program? 
The 8086 can generate 16-bit of I/O address. Thus it can address up to 64 Kbyte I/O locations or 32 K word I/O locations.