FEDERAL PUBLIC SERVICE COMMISSION
COMPETITIVE EXAMINATION FOR RECRUITMENT TO POSTS
IN BPS-17 UNDER THE FEDERAL GOVERNMENT, 2023

COMPUTER SCIENCE, PAPER-II

TIME ALLOWED: THREE HOURS

PART-I (MCQS): MAXIMUM 30 MINUTES

PART-I (MCQS) MAXIMUM MARKS = 20

PART-II MAXIMUM MARKS = 80

NOTE

(i) Part-II is to be attempted on the separate Answer Book.

(ii) Attempt ONLY FOUR questions from PART-II by selecting TWO questions from EACH SECTION. All questions carry equal marks.

(iii) All parts of each question must be attempted at one place instead of at different places.

(iv) Candidate must write the question number in the Answer Book according to the question number in the question paper.

(v) No page or space should be left blank between the answers. All blank pages of the Answer Book must be crossed.

(vi) Extra attempt of any question or any part of an attempted question will not be considered.

Q. 2

(a) Suggest reasons why RAMs have traditionally been organized as only one bit per chip, whereas ROMs are generally organized with multiple bits per chip. (7)

(b) Consider a dynamic RAM that requires a refresh cycle 64 times per millisecond. Each refresh operation requires 150 ns, while a memory cycle requires 250 ns.

Calculate what percentage of the memory's total operating time must be devoted to refresh operations. (7)

(c) In the context of RAID, explain the distinction between:

• Parallel access
• Independent access

(6)

Q. 3

(a) The CPU of a router can process 2 million packets per second, while the offered load is 1.5 million packets per second. If a route from source to destination contains 10 routers, calculate the total time spent in queuing and CPU servicing. (7)

(b) An IP datagram using the strict source-routing option has to be fragmented.

Should the source-routing option be copied into every fragment, or is it sufficient to place it only in the first fragment?

Explain your answer. (7)

(c) Give:

• Two examples of computer applications where connection-oriented service is appropriate.
• Two examples where connectionless service is more suitable.

(6)

Q. 4

(a) A 32-bit computer has two selector channels and one multiplexor channel.

Each selector channel supports:

• Two magnetic disk units
• Two magnetic tape units

The multiplexor channel has:

• Two line printers
• Two card readers
• Ten VDT terminals

The assumed transfer rates are:

Estimate the maximum aggregate I/O transfer rate of the system. (12)

(b) Consider a program that accesses a single I/O device. Compare unbuffered I/O with the use of a buffer.

Show that using a buffer can reduce the running time by at most a factor of two. (8)

Q. 5

(a) An I/O-bound program spends more time waiting for I/O than using the processor when running alone, whereas a processor-bound program has the opposite characteristic.

Suppose a short-term scheduling algorithm favors programs that have used little processor time in the recent past.

Explain why this algorithm favors I/O-bound programs, while still ensuring that processor-bound programs are not permanently denied processor time. (10)

(b) Originally, a Class B address used 16 bits for the network portion. Suppose instead that 20 bits had been used for the network portion.

How many Class B networks would there have been? (5)

(c) Explain the distinction between:

• Instruction-level parallelism
• Machine parallelism

(5)

SECTION-B

Q. 6

(a) Explain the following SELECT statement search conditions with examples, using any database schema of your choice:

1. Compound comparison search condition
2. Range search condition — BETWEEN / NOT BETWEEN
3. Set membership search condition — IN / NOT IN
4. Pattern matching search condition — LIKE / NOT LIKE

(12)

(b) Explain the ACID properties of a database transaction. (4)

(c) Explain transitive dependency with a suitable example. (4)

Q. 7

(a) A common measure of digital-data transmission is the baud rate, defined here as the number of bits transmitted per second. Transmission generally consists of:

• One start bit
• One byte (8 bits) of information
• One stop bit

Using these facts, calculate:

(i) How many minutes would be required to transmit a 1024 × 1024 image with 256 intensity levels using a 56K baud modem?

(ii) What would the transmission time be at 750K baud, representative of a phone DSL connection?

(10)

(b) What effect would setting the lower-order bit planes to zero generally have on an image histogram? (5)

(c) What would be the effect on the histogram if the higher-order bit planes were set to zero? (5)

Q. 8

(a) Explain how Search Engine Optimization (SEO) improves website traffic.

Provide proper reasons and suitable coding examples. (8)

(b) Suppose a web development team is going to make a contract with a customer and needs to estimate the cost of application development.

Discuss the pricing factors that should be considered when estimating the development cost. (8)

(c) Write jQuery code to slide elements up and down.

DOWNLOAD NOW