In Unix operating systems, which of the following is not a standard process state?

Introduction / Context:
Unix like operating systems describe processes using a small set of well defined states that indicate whether a process is executing, ready, blocked or finished. Knowing these states is helpful when interpreting diagnostic tools such as ps. This question asks you to identify which term is not traditionally used as a distinct process state name in classic Unix descriptions.

Given Data / Assumptions:

• We are considering classic Unix process state terminology.
• Common states include running, sleeping or waiting, stopped and zombie.
• Some tools may use slightly different labels, but the conceptual states are standard.
• No numeric calculation is needed.

Concept / Approach:
Traditional Unix documentation often describes processes as running, sleeping, stopped or zombie. A ready or runnable process is conceptually distinct from running, but many tools group ready and running together as simply running. The explicit label runnable is not always presented as a separate canonical state in basic descriptions. Therefore, when the question asks which among the options is not a process state in Unix, runnable is the best choice, because running, zombie and stopped clearly appear as named states in common references.

Step-by-Step Solution:
Step 1: Recall the typical list of Unix process states: running, sleeping or waiting, stopped and zombie. Step 2: Note that running represents processes actively using the CPU or ready to run. Step 3: Recognise that zombie is a special state for processes that have terminated but whose exit status has not yet been collected. Step 4: Recognise that stopped describes a process that has been suspended by a signal. Step 5: Conclude that runnable, as a separate label, is not usually listed as a distinct canonical state name in basic Unix state lists.

Verification / Alternative check:
If you look at standard Unix references, you will find descriptions of process states including running, sleeping, stopped and zombie. Some internal kernel structures may represent ready and running separately, but user facing commands commonly show running and do not list runnable as a separate state. This supports the identification of runnable as the option that does not match the usual state names.

Why Other Options Are Wrong:
Option A, running, is clearly a standard state that appears in all process state diagrams. Option C, zombie, is a well known state where the process has finished but still has an entry so the parent can read the exit status. Option D, stopped, is also a standard Unix process state that occurs when a process is suspended, for example by a job control signal. These three are all legitimate states, unlike runnable as a named category in basic lists.

Common Pitfalls:
A common confusion is between the conceptual idea of a runnable process and the specific labels used by Unix tools. Some systems may internally distinguish ready and running, but the question is about standard state names, not internal flags. Make sure to focus on the labels you see in typical ps output and textbook diagrams when answering questions like this.

Final Answer:
Runnable is not traditionally listed as a separate standard process state name in Unix.