ITPEC FE Morning April 2019 Question 18

Buffer overflow condition — find minimum buffer size when send speed exceeds receive speed.

Given: send speed S, receive speed R, duration T, buffer size L, where S > R.

• •Data entering buffer per second: S
• •Data leaving buffer per second: R
• •Net accumulation per second: S - R
• •Over T seconds, buffer must hold: (S - R) × T

Buffer does not overflow when: `L ≥ (S - R) × T`

Answer: (d)

Why not others:
- (a) L < (R - S) × T — R - S is negative (since S > R), and < means overflow
- (b) L < (S - R) × T — correct difference but < means buffer is too small
- (c) L ≥ (R - S) × T — R - S is negative, so L ≥ negative is always true (meaningless)

Key rule: When producer is faster than consumer, net accumulation = (S - R) × T; buffer must be ≥ this value.

AI-generated — may contain errors