# Advanced level 2024 HIHS mock computer science 2

### Advanced level 2024 HIHS mock computer science 2

Advanced level 2024 HIHS mock computer science 2

Computers use 2’s complement to easily perform operations
i) Give the range of numbers that can be represented in two’s complement given n bits. (1 mark)
ii) Using 7 bits, add 63 and -64 in 2’s complement. (3 marks)
b) A floating point binary number 11101011 is stored using 5 bits for the mantissa and 3 bits for the exponent, both
in 2’s complement form. Show how this number can be normalized. (2 marks)
i) Find the denary equivalent of the normalized number (2 marks)
c) Explain the main difference between a sequential and combinational logic circuit. (2 marks)
d) From the truth table below;
i) Deduce the Boolean expression for sum and carry, and then draw the logic circuit diagram. (4 marks)
X Y sum carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 1 1
ii) Using Boolean identities, Proof that XNOR gate is the complement of a X’OR gate. (3 marks)
2)
a) Briefly explain the difference between the followings
i) Computer architecture and computer organization. (2 marks)
ii) Polling and interrupt. (2 marks)
b)
i) What do you understand by the term addressing mode as used in computer architecture? (2 marks)
ii) Suppose the notation #K denotes “take value of K” and R1 R2 R3 are registers. If ADD is an opcode and (R1
R2 #R3) and (R2,#10) are operands. State for each set of operands, the addressing mode used and how it
works with the ADD opcode. (4 marks)
c) A microprocessor has RAM chip with capacity of 128 x 8.
i) How many of these memory chips are needed to provide a memory capacity of 2KB. (2 marks)
ii) And how many address lines must be used to access the memory. (2 marks)
iii) How many of these lines will be common to all chips? (1 marks)
d) Briefly explain the concept of pipelining and how it affects machine performance. (2 marks)
3)
a) In the context of process management, define throughput, response time, critical section, context switch. (4
marks)
b) Two types of processes in the operating system (OS) are I/O bound and CPU bound processes. How do they
differ? (2 marks)
c) Consider the table given below about a set of processes to be executed by the processor