Saturday, 6 April 2013

week 3

Software Layers: Operating system, Drivers, System Software, Application programs
                                                            Software layer
Operating System
> OS receives order from the user via application program
> It has programs and routines that control all accesses to hardware
> Higher levels are protected from any issues
   - Multiple users
   - Multiple requests for the same resource
   - Access control
> When the OS determines its safe to proceed, direct calls to device drivers are performed

System software
> What is system software?
> Type of system software:
   - Operating  systems
   - Utility programs
> Operating system = a set of programs that coordinates all the activities among computer hardware  resources
> Utility programs = a set of programs that allows a user  ti perform maintenance - type concerning  the computer itself, its devices and its programs
Low - Level  Language
> Two type:
  - Machine Language
  - Assembly Language 
> Machine language = the first generation PL
> Assembly language = the second generation PL
Machine language
> Uses a series of binary digits (1s and 0s) or combination of numbers and letters that represent binary digits
> The binary digits corresponds to the ON and OFF electrical states 
Assembly Language
> Program  is written using symbolic instruction codes called mnemonic 
Also uses symbolic memory addresses
Assembly language must be converted into machine language before the computer  can execute the program

Standard Software packages : Overview and typical installation procedures

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