IT and Communication Engineering
IT and Communication Engineering in IESL Part I covers algorithms and data structures, operating systems, databases, computer networks, cybersecurity, and communication theory including bandwidth, noise and capacity.
Core rules and concepts
- Algorithm complexity: big-O describes growth; binary search is O(log n), and simple nested loops are often O(n²).
- IPv4 subnetting: a /26 mask (255.255.255.192) gives 64 addresses per subnet, of which 62 are usable after network and broadcast addresses.
- TCP is connection-oriented and reliable; UDP is connectionless with lower overhead.
- Shannon capacity C = B log2(1 + S/N); Nyquist signalling rate = 2B log2 M for M levels.
- Decibels: dB = 10 log10(P2/P1) for power and 20 log10(V2/V1) for voltage.
- Databases: normalisation reduces redundancy; ACID describes transactions.
Worked example
Subnet 192.168.10.0/26. The block size is 64, so subnets begin at .0, .64, .128 and .192. For the first subnet, the usable host range is 192.168.10.1 to 192.168.10.62 and the broadcast address is 192.168.10.63. If 100 hosts are required, /26 is insufficient because it offers only 62 usable addresses; /25 provides 126 usable hosts. The reasoning is to subtract the network and broadcast addresses and compare with the host requirement.
Traps that cost marks
- Counting the network and broadcast addresses as usable hosts.
- Using 10log10 for voltage ratios instead of 20log10.
- Inserting a linear signal-to-noise ratio into Shannon’s formula when dB was given.
- Confusing bandwidth with throughput, or TCP header size with payload.