What are the differences between a Program, an Executable, and a Process?

In simple words -

Program: Program is a set of instructions which is in human readable format.(HelloWorld.c)

Executable: Executable is a compiled form of a Program (HelloWorld.exe file)

Process: Process is the executable being run by OS. The one you see in Task Manager or Task List (HelloWord.exe Process when we double click it.)

A Program or Computer Program essentially provides a sequence instructions (or algorithms if you rather) to the operating system or computer. These computer programs come in an executable form that the Operating System recognizes and can use to directly execute the instructions.

Essentially, an Executable is a file in a format that the computer can directly execute as opposed to source files which cannot be directly executed and must first be compiled. An executable is the result of a compilation. I mentioned that the operating system recognizes executable, it does so via the extension. A common extension used for windows executable files is .exe.

Once an executable has been executed a process begins. A process is simply an instance of a computer program. You can think of a process as the execution of the instructions contained in a computer program. When you view the Task Manager on a Windows computer you can see all of the current processes. Processes own resources such as virtual memory, operating system descriptions (handles, data sources, sinks etc), security attributes and various other elements required to process effectively.