Computer Organization and Fundamentals
What the examiner tests
Computer Organization and Fundamentals covers the machine beneath a program: CPU organisation, memory hierarchy, data representation and basic logic. Questions often ask you to convert between number systems, interpret truth tables, or choose the correct memory/device for a situation.
Core rules
- CPU: ALU performs arithmetic/logic; control unit fetches/decodes/executes; registers hold temporary data; cache is fast SRAM close to CPU.
- Memory hierarchy: registers → cache → RAM → secondary storage. RAM is volatile; ROM is non-volatile. Cache improves speed, not capacity.
- Number systems: binary base 2, octal base 8, decimal base 10, hexadecimal base 16. Group binary digits from the right into 3 for octal and 4 for hexadecimal.
- Logic gates: AND outputs 1 only for 1,1; OR for any 1; NOT inverts; XOR is 1 for different inputs; NAND/NOR are negated outputs.
Worked example
Convert decimal 45 to binary and hexadecimal. Repeated division by 2 gives remainders 1,0,1,1,0,1 read bottom-up: 45₁₀ = 101101₂. Group 101101 from the right in fours: 0010 1101 = 2D₁₆. Check: 2×16 + 13 = 45. The leading zeros in the hex grouping are added only to complete a group.
Traps
Do not call cache secondary storage; do not say ROM loses data on power-off. When converting, read remainders in the correct order. A half adder has no carry input. Keep binary grouping aligned from the least significant bit.