Computer Science: Fundamentals

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your NAT-I exam.

Computer Science Fundamentals for NAT-I tests factual recall of how computers store, process, and transmit data. The five highest-yield areas are number systems, hardware organisation, software types, networking basics, and data representation.

Must-Know Fact	Value
1 byte	8 bits
1 KB (binary)	1024 bytes
IPv4 address length	32 bits (e.g. 192.168.1.1)
ASCII character size	1 byte per character

CPU = ALU + Control Unit + Registers; executes instructions.
RAM is volatile, ROM is non-volatile — a classic MCQ trap.
Compiler translates the whole program first; interpreter translates line-by-line.

🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months before NAT-I.

Number System Conversions

Conversions between Decimal, Binary, Octal, and Hexadecimal appear almost every testing cycle. The rule for decimal-to-binary is: divide by 2 repeatedly and read remainders bottom-up. For hex, divide by 16. Hex-to-binary requires padding each hex digit to exactly 4 bits (e.g. A3₁₆ = 1010 0011₂) — a frequent source of off-by-one mistakes.

Hardware and Software Layers

The CPU contains the ALU (arithmetic/logic operations), the Control Unit (fetches and decodes instructions), and Registers (fastest on-chip memory). Primary memory splits into RAM (volatile, loses data on power-off) and ROM (non-volatile, holds boot firmware). System software (operating systems, compilers, device drivers) manages hardware, whereas application software performs user-facing tasks such as word processing.

Layer	Examples	Role
Hardware	CPU, RAM, Hard disk	Physical components
System software	Windows, Linux, Compiler	Manages hardware
Application software	MS Word, Chrome	End-user tasks

Programming Language Generations

Languages progress from 1GL (machine code) through 3GL (C, Java — procedural/structured) to 5GL (Prolog — natural-language-like). Each generation trades control for abstraction.

Algorithm representation uses flowcharts (oval = start/end, rectangle = process, diamond = decision) or pseudocode.
Database systems rely on a primary key for unique rows and a foreign key to reference another table.
Network topologies: star (central hub), bus (single backbone), ring (closed loop), mesh (every node connected).

🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students with a longer runway before the test.

Storage and Data Representation

Every unit scales by a factor of 1024 in binary interpretation: 1 KB = 1024 B, 1 MB = 1024 KB, 1 GB = 1024 MB. Storage questions often test whether a 1 MB file of plain ASCII text contains exactly 1,048,576 characters (because each ASCII char = 1 byte). Unicode UTF-8 characters, by contrast, occupy 1 to 4 bytes — a key distinction when calculating file size.

Networks and the Internet

An IP address is a logical address assigned by software; the MAC address is the hardware identifier burned into the NIC. The URL https://www.nts.org.pk/results breaks down into scheme (https) → subdomain (www) → domain (nts.org.pk) → path (/results). DNS translates domain names to IP addresses, while HTTP/HTTPS governs request-response communication, with HTTPS adding TLS encryption.

Cyber Safety and Common Malware

Malware Type	Behaviour	Spread Method
Virus	Attaches to a host file	Requires user action
Worm	Self-replicating	Spreads across networks
Trojan	Disguised as legitimate software	Social engineering
Ransomware	Encrypts files for payment	Phishing emails

Practice Prompts

Convert the decimal number 173 into binary and hexadecimal, then convert 7F₁₆ back into binary and decimal.
A 512 MB flash drive holds ASCII text files of exactly 1 MB each. How many files can it store, and what is the equivalent capacity in bytes?

Exam Tip: NAT-I rarely asks code-writing. Focus on recognising definitions, distinguishing look-alike pairs (RAM/ROM, Compiler/Interpreter, IP/MAC), and converting between bases without arithmetic slips.

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Computer Science: Fundamentals