Components

This section is the entry point for understanding the major subsystems that make up the Go distribution. Each subsystem corresponds to one or more directories under src/.

The toolchain

These tools are what produces a Go program from source. They all live under src/cmd/.

Component	Directory	Page
Compiler (gc)	src/cmd/compile/	Compiler
go command	src/cmd/go/	Go command
Linker	src/cmd/link/	Linker
Assembler	src/cmd/asm/	Assembler
cgo	src/cmd/cgo/	cgo

Other tools you'll see in src/cmd/ but don't have dedicated pages here:

• cmd/dist — the build coordinator (used by make.bash); see Architecture.
• cmd/gofmt — the formatter; behavior is in go/format and go/printer.
• cmd/vet — the static analyzer; uses golang.org/x/tools/go/analysis (vendored).
• cmd/cover, cmd/covdata, cmd/preprofile — coverage and profiling helpers.
• cmd/pprof, cmd/trace, cmd/objdump, cmd/nm, cmd/addr2line, cmd/buildid, cmd/pack, cmd/test2json, cmd/distpack, cmd/relnote — assorted developer tools.

The runtime

The runtime is what every compiled Go binary embeds. It manages goroutines, memory, and OS interaction.

Component	Directory	Page
Runtime (scheduler, GC, allocator, etc.)	src/runtime/	Runtime

The standard library

Hundreds of packages under src/. Documented as a single overview page:

Component	Directory	Page
Standard library	src/<pkg>/...	Standard library

How they fit together

graph TD
    User[User .go source] --> GoCmd[cmd/go]
    GoCmd -->|drives| Compile[cmd/compile]
    GoCmd -->|drives| Asm[cmd/asm]
    GoCmd -->|drives| Cgo[cmd/cgo]
    GoCmd -->|drives| Link[cmd/link]
    Compile --> Object[.a object archive]
    Asm --> Object
    Cgo --> Compile
    Object --> Link
    Link --> Binary[Executable]
    Binary -.embeds.-> Runtime[runtime]
    Binary -.uses.-> StdLib[Standard library]
    StdLib -.runtime calls.-> Runtime

Each page below dives into one of these boxes. Start with the compiler if you want to understand "how is my Go code turned into machine code?" Start with the runtime if you want to understand "what happens when my Go program runs?"

Cross-cutting

• Go command is the orchestrator. It is the public face of the toolchain and where most user-visible behavior lives.
• cgo is technically a preprocessor + a runtime collaboration. It bridges Go and C.
• Standard library covers the library packages and their organization.