Relationship between OS, app, and H/W

• OS give permission and allocate memory that app requests (Manage H/W resources)
• OS provide CPU time that app requests
• OS give permissions for using I/O devices that app requests

OS provide interfaces

• For user interface
  • Shell
    • A program that allow user to manipulate OS functions and services
    • CLI / GUI
• For APP interface
  • API (Application Programming Interface)
    • Provide functions
    • open()
  • Usually provided as library format
    • C library https://www.gnu.org/software/libc
• System Call
  • OS provide command / function called system call to use OS’s functions requested by APP
  • Most API consists of calling system call

  

If want to make OS?

1. Implement OS (kernel)
2. Implement sys. call
3. Implement C API (library)
4. Implement Shell program
5. Develop application programs