Process

Definition

A process is a running program.

Machine State

The process's machine state consists of: memory, registers (including special registers like program counter), stack pointer, frame pointer

Process API

• Create

• Destroy

• Wait

• Miscellaneous Control: suspend, resume, ...

• Status

Process Creation

1. Load code and static data into memory

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2. Allocate memory for the program's run-time stack

3. Create initial memory for the program's heap

Process States

• Running

• Ready

• Blocked

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UNIX Process API

fork()

Create a new process. For the parent process, returns the PID of the child process; for the child process, returns 0.

wait()

Wait for a child process to finish.

exec()

Run a program that is different from the calling program on the current process.

Motivating the API

The separation of fork() and exec() allows the shell to do things after fork() and before exec(), such as redirecting the input and output.