Information, Electronics and Communications Technology (IECT)
The IECT domain is the shared technical foundation of the NIELIT ECC examination, testing whether you can move confidently between data representation, digital logic, basic electronics, and the communication and networking layers that carry information. Items are short and factual - a definition, a truth table, a unit conversion, a one-line numerical - so exact units and conventions earn the marks.
Core rules and concepts
- 1 byte = 8 bits; 1 KiB = 1024 B, while 1 kB (SI) = 1000 B. An n-bit two's complement integer spans −2^(n−1) to 2^(n−1)−1. One hex digit = 4 bits; one octal digit = 3 bits.
- NAND and NOR are universal gates; De Morgan gives (A·B)′ = A′+B′ and (A+B)′ = A′·B′. Adders and multiplexers are combinational; flip-flops store state.
- Silicon diode forward drop ≈0.7 V, germanium ≈0.3 V. Voltage gain in dB = 20 log(V₂/V₁), power gain 10 log(P₂/P₁); +3 dB doubles power, +6 dB doubles voltage.
- AM bandwidth = 2f_m; Carson's rule for FM ≈ 2(Δf + f_m). Nyquist rate = 2B samples/s; Shannon capacity C = B log₂(1 + S/N).
- OSI has 7 layers, TCP/IP 4. IPv4 is 32 bits, IPv6 128. Private IPv4 space: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
Worked example
On 192.168.10.0/26, find the third usable subnet. A /26 borrows 2 host bits, so the mask is 255.255.255.192 and the block size is 256 − 192 = 64. Bases step 0, 64, 128, 192; the third is 192.168.10.128. Its broadcast is one below the next base (.191), leaving .129–.190 - 62 usable hosts, not 64, because network and broadcast addresses are reserved. General rule: usable hosts = 2^h − 2, where h is the host-bit count.
Traps that cost marks
- Confusing dB (a ratio) with dBm (power relative to 1 mW).
- Using 1000 instead of 1024 when the question says KiB or memory size.
- Quoting Nyquist as f_max rather than 2f_max for a band-limited signal.
- Calling a MAC address routable - it is a 48-bit layer-2 identifier, while IP is layer 3.