Computer Fundamentals and Organization
Computer Fundamentals and Organization tests how a computer represents, stores, moves and processes data: number systems, logic gates, CPU registers, memory hierarchy, I/O and storage. Expect direct conversion and device-comparison questions rather than programming.
Core rules
- A bit is one binary digit; a byte is 8 bits. 1 KiB = 1024 bytes, while decimal 1 KB = 1000 bytes; exam questions usually mean binary unless stated.
- CPU: the ALU does arithmetic and logic; the control unit fetches, decodes and executes; registers such as PC, IR, MAR and MBR are the fastest storage.
- Memory hierarchy: registers > cache > RAM > SSD/HDD > tape. Cache exploits locality of reference.
- RAM is volatile primary memory; ROM is non-volatile firmware. Secondary storage is non-volatile.
- Logic gates: AND, OR, NOT, NAND, NOR, XOR. NAND and NOR are universal gates.
Worked example
Convert 101101 base 2 to decimal and hexadecimal. Place values from the right give 1 + 4 + 8 + 32 = 45. For hex, group bits from the right: 0010 1101 = 2D base 16. Reasoning: binary-to-decimal uses powers of 2; binary-to-hex groups four bits because 16 = 2 to the power 4.
Traps
Do not write decimal 45 as 101101 in BCD; BCD 45 is 0100 0101. Do not confuse storage size with address size. In 2's complement, the leftmost bit has negative weight. Cache is smaller but faster than RAM, not larger.