Direct Execution

Reorder the first five steps of a basic direct execution.

• The OS creates an entry for a process list

• The OS sets up the stack with argc/argv

• The OS allocates memory for a program

• The OS clears registers

• The OS loads a program into memory

Reorder the next five steps of a basic direct execution.

• The OS calls main()

• The program returns from main()

• The OS frees the memory of a process

• The program runs main()

• The OS removes the entry from the process list

___________ mode allows code to perform privileged operations. This is where the OS runs.

_________ mode limits the capabilities of the programs that run in this mode.

Which of the following is a way for a user program to request privileged services from the kernel?

• System Calls

• Trap Tables

• Trap Instructions

• LDE Protocols

​ A​ (a)   tells the hardware what code to run when specific events occur. A​ (b)   jumps into the kernel and raises the privilege level to​ (c)   , and calls​ (d)   to go back into​ (e)   .

• trap table
• trap instruction
• kernel-mode
• return-from-trap
• user-mode

In a cooperative system, how does the OS regain control of the CPU?

• The OS regains control of the CPU every five seconds.

• The OS does not need control of the CPU; it can perform any task while other processes are running.

• The OS regains control of the CPU when the user program attempts unauthorized activity.

• The OS regains control of the CPU when the user program makes a system call.

Which of the following describes a timer interrupt?

• It jumps into the kernel to raise privilege level.

• It requires a system reboot to regain control.

• It assumes that processes will behave reasonably

• It is programmed to raise an interrupt every period of milliseconds.

How does the OS retain state as it switches processes?

• The OS saves the information on the hard disk.

• The OS cannot save state when switching processes.

• The OS saves the information to RAM.

• The OS saves the information to the kernel stack.