Use Normally DOS can run only one program at a time. When a program finishes, it returns control to DOS using the system call of the DOS API. HelpPC reference: INT 21,0 – Program Terminate The memory and system resources used are then marked as unused. This makes it impossible to restart parts of the program without having to reload it all. However, if a program ends with the system call or , the operating system does not reuse a certain specified part of its memory.
Use Normally DOS can run only one program at a time. When a program finishes, it returns control to DOS using the system call of the DOS API. HelpPC reference: INT 21,0 – Program Terminate The memory and system resources used are then marked as unused. This makes it impossible to restart parts of the program without having to reload it all. However, if a program ends with the system call or  the operating system does not reuse a certain specified part of its memory.