Operating System

Operating System

1. control the execution of application programs

2. acts as an interface between applications and the hardware

3. memory management

   • swapping
   • memory is subdivided to accomodate multiple process
   • partitioning
     • fixed-size paritions
     • variable-size partitions
     • logical adress - location relative to the beginning of the program
     • physical address - actual location in main memory
   • paging
     • pages
     • page frames
     • Virtual memory
       • demand paging
       • page replacement
         • LRU (last recently used)
         • FIFO
       • allows for very effective multiprogramming and relieves the user of the unnecessarily tight constraints of main memory
   • segmentation
     • view memory as consisting of multiple address spaces or segments

4. gerenciador de processos

   • Types
     • interactive
     • batch
     • multiprogramming
       • scheduling types
         • Long-term scheduling
         • Medium-term scheduling
         • Short-term scheduling
           • process states
             • New/Ready
             • Run
             • Wait
             • Halt
           • PCB (Process Control Block) / Descritor de processo
             • informações relativas ao processo
             • chaveamento de contexto
               • time slice (tempo de processamento)
             • Fila de PRONTOS, Fila de BLOQUEADOS
         • I/O scheduling
       • comunicação entre processos (IPC)
         • Pipe
       • Threads
         • fluxo de execução do processo
         • não compartilha o contexto de hardware
         • tipos
           • usuário
           • núcleo
           • híbrido
     • uniprogramming
       • one task at time
   • foreground x background
   • I/O-bound x CPU-bound
   • paralizações
     • interrupções (hardware)
     • exceções (software)

5. gerenciar I/O

6. gerenciar sistema de arquivos

7. modo de operação

   • modo usuário
   • modo kernel