Computer Fundamentals and Hardware
This section tests the block diagram of a computer, the job of each unit, memory types and capacities, and number-system conversions - the short-answer and one-mark questions that open most papers.
Functional units
A computer has five blocks: input unit, output unit, memory unit, arithmetic logic unit (ALU) and control unit (CU). ALU + CU + registers = CPU. The CU fetches and decodes instructions and issues control signals; the ALU performs arithmetic and comparisons; registers are the fastest storage, inside the CPU; the system bus carries data, addresses and control signals.
Memory
- Primary: RAM (volatile; SRAM = flip-flops, fast, used for cache; DRAM = capacitors, cheaper, main memory) and ROM (non-volatile: PROM, EPROM, EEPROM).
- Secondary: magnetic (HDD), solid-state (SSD, pen drive), optical (CD 700 MB, DVD 4.7 GB).
- 1 byte = 8 bits; 1 KB = 1024 B; 1 MB = 1024 KB; 1 GB = 1024 MB; 1 TB = 1024 GB.
- Cache sits between CPU and RAM: small but fastest of the memory hierarchy.
Number systems
Binary (2), octal (8), decimal (10), hexadecimal (16); hex uses 0–9 and A–F.
Worked example
Convert 11011010₂ to hexadecimal and decimal. Hex: group in fours from the right → 1101 1010 → D A → DA₁₆. Decimal: place values 128+64+0+16+8+0+2+0 = 218. Check: D = 13 → 13×16 = 208, plus A = 10 → 218. ✔
Traps
- Calling the CU the unit that does calculations - that is the ALU.
- Saying ROM is volatile, or that RAM keeps data after shutdown.
- Writing 1 MB = 1000 KB; this paper expects 1024.
- Converting hex to binary via decimal instead of expanding each hex digit to four bits.