Unit 2 — 5-minute revision
- Binary: base 2, digits 0–1 | Octal: base 8, digits 0–7 | Decimal: base 10, digits 0–9 | Hex: base 16, digits 0–9, A–F
- Conversions: decimal→other = repeated division; other→decimal = positional multiplication; binary↔octal = group in 3 bits; binary↔hex = group in 4 bits
- Gates: AND (1 only if all 1), OR (1 if any 1), NOT (inverts), NAND (AND then invert), NOR (OR then invert), XOR (1 if odd number of 1s), XNOR (invert of XOR)
- Universal gates: NAND and NOR — any circuit can be built from them alone
- Machine language: 0s and 1s, CPU-direct, fastest; Assembly: mnemonics + assembler; HLL: English-like, portable, needs translator
- Compiler: translates whole program at once, creates object code, fast execution (C, C++); Interpreter: line-by-line, slower, easy debugging (Python)
- System software: OS, compilers, assemblers; Application software: MS Word, Excel — runs on system software
- Assembler's job: converts assembly to machine code; Linker's job: joins object code into an executable
🔥 High-yield: NAND/NOR are universal gates; compiler = whole program, interpreter = line-by-line; assembler converts assembly language; 1 hex digit = 4 binary digits.
| Term | Full form |
|---|---|
| ASCII | American Standard Code for Information Interchange |
| EBCDIC | Extended Binary Coded Decimal Interchange Code |
| Unicode | Universal character encoding (16-bit/32-bit) |
| BIT | Binary Digit |
| HLL | High Level Language |
| LLL | Low Level Language |
| GUI | Graphical User Interface |
| CLI | Command Line Interface |