Advanced level 2023 south west regional mock computer science 2

Figure 1 shows an 8-bit pattern.

10110110 Figure 1

(a) If the bit pattern in Figure 1 is a two’ s complement binary integer, what is the denary equivalent of this bit pattern? ( -‘ (2marks)

b) What is the range of denary numbers that can be represented using 8 bit two s complement binary integers0

(c) What is the hexadecimal equivalent of the bit pattern in Figure 1?
(d) Why are bit patterns often displayed using hexadecimal instead of binary?

(ii)(a) Simplify the Boolean expression B (A + B).
(b) Draw a logic circuit diagram for the expression Q = A • B 4- (A ® B).

(2 marks) (2 marks) (1 mark)

(3 marks) (3 marks

(c) Ignoring cost, state two advantages of simplifying a Boolean expression before it is implemented in hardware.

(2 marks)

2. (i) (a) The size of the memory in a computer system is 512 mega words where each word is 32 bits. Determine the size of the address bus and the size of the data bus. (3 marks)

( b) How many memory chips of capacity 128 by 8 are needed to provide a memory capacity of 4096 by 16? (2 marks) (c) What is cache memory? How is cache memory different from main memory? (3 marks)

(ii)(a) RISC processors use of a load/store architecture. Explain the implication of the load/store architecture on RISCinstruction sets. (2 marks)

(b)Slate two advantages of RISC processors over CISC processors. (2 marks) (c) Consider the high-level language statement: C – A + B. that instructs the computer to add the values of two variables

A and B, and then assign the sum to a variable C.
Using the mnemonics LDR, ADD and STR which represent the operations load, add and store respectively, show how

the above statement would be evaluated in a load/store based CPU organization. (4 marks)

3. (i)(a)Whatisaschedulingpolicyinoperatingsystems? (1mark)(b) Describe the terms throughput and turnaround time as used in scheduling, staling how each can be used as a metric for a given scheduling policy. (4 marks) (c) Explain what a convoy effect is and state a scheduling policy that could cause convoy effect when scheduling

processes.

(3 marks )

(2 marks) (2 marks) (c) Describe how’ virtual memory can allow a w’ord processor and a spreadsheet to run simultaneously on a computer even when both applications are too large to fit into the computer’ s main memory’ (3 marks)

(ii)(a) State two activities of the operating system in relation to memory management. (b) Explain the difference between a virtual address and a physical address.

(d) State two advantages of dynamic partitioning in contiguous memory allocation. (2 marks :

4. (i) A bank uses a computer file to store customer records. One field in the the customer record is a 4-digil customer ID (in the range 1000 and 1999).

The file can store a maximum of 1024 records. An algorithm for inserting a new record in this file uses the following

hash function:

RecordKey= CustomerIDmodl 024, where RecordKey is the record ‘ s position in the file and mod is the modulus arithmetic operator.