What are instances of running programs within an operating system?

• A. Processes
• B. Threads
• C. Services
• D. Executables

Answer: (A)

When a program runs, the operating system creates a process—the running instance of that program. A process has its own memory space, code and data, CPU state, and the resources it uses, plus a unique process identifier. The OS schedules this process, allocates time on the CPU, and manages it as it runs, possibly alongside many other processes. A process can contain multiple threads, which are separate paths of execution that share the process’s memory and resources. Services are typically long-running background processes that provide functionality, so they’re still processes. Executables are the actual program files that contain the code to run; they become processes only after the OS loads them and starts execution. So the running instance of a program is a process.