A compiler bridges the gap between human-readable logic and processor circuits. It performs a top-down transformation:
High-level source (C):
int a = 5, b = 3, c;
c = a + b;
Compiler phases:
Assembly (Human-readable machine code):
ADDI r1, r0, 5 ; Load 5 into register 1
ADDI r2, r0, 3 ; Load 3 into register 2
ADD r3, r1, r2 ; r3 = r1 + r2
Machine Code (Binary for the processor):
0001 0000 0001 0101 (hypothetical 16-bit encoding) A compiler bridges the gap between human-readable logic
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| Layer | Core Components | Abstraction | |-------|----------------|--------------| | Gates | Transistors, diodes | Boolean logic | | Circuits | Half/full adders, latches | Data flow & storage | | Processor | ALU, CU, cache | Instruction execution | | Compiler | Parser, optimizer, code gen | Language translation | | Computer | CPU, RAM, disk, bus | Programmable system | Compiler phases:
At the lowest physical level, computers deal with electricity. We represent the presence of voltage as 1 (True) and the absence as 0 (False). Logic gates are physical devices that implement Boolean algebra to manipulate these binary signals.
At the physical level, a computer is a collection of transistors. A transistor is simply an electronic switch that can either block electricity (0) or let it through (1). By combining these transistors in specific patterns, we create logic gates. Assembly (Human-readable machine code): ADDI r1, r0, 5
Logic gates are the atomic units of digital computation. They take one or two binary inputs and produce a single binary output based on a boolean function.
Individual gates are useless in isolation. When combined, they form combinational and sequential circuits.