Computing

Computing

1. Computing Hardware

   • Binary Logic
     • Logic Gates
       • AND Gate: Both inputs must be 1
       • OR Gate: Either inputs can be 1
       • NOT Gate: The input is reversed.
     • Truth Tables
       • AND: 0 0 = 0 1 0 = 0 0 1 = 0 1 1 = 1
       • OR: 0 0 = 0 1 0 = 1 0 1 = 1 1 1 = 1
       • NOT: 0 = 1 1 = 0

2. Software

   • Software is computer programs.
   • System Software
     • Programs which are required for the computer to work.
     • Utilities
       • Examples
         • System defragmentation
         • File transfer
         • Virus detector
     • Operating System
       • Memory Management
       • Multi-tasking
     • Translators
       • Translate high-level (e.g. python) to low-level code which the processor can execute.
         • Compiling
           • The whole code is translated into low-level code and executed.
         • Interpreting
           • The code is translated and executed one line at a time.
   • Application Software
     • Programs which perfom tasks which would have to be done if computers did not exist.
   • Writing Software
     • Use a Developer (off the shelf)
     • Proprietary
       • The software is 'owned'.
     • Open Source
       • The software begins as source code. Everyone is allowed to make changes. If a change is made, the source code forks to different code. If someone makes a change and the original developer decides to include it in the source, then it is called upstreaming.
   • Operating System Functions
     • Always running.
     • Memory Management
       • The kernel has complete access to the memory of the computer. It's role is to safely allow access the memory that the programs require.
     • Multi Tasking
       • The kernel allows programs to run concurrently (they overlap instead of running at the exact same time). This gives the impression of multi tasking.
     • User Interface
       • Essential for human interaction. Usually command line or GUI
     • Security
       • The OS must be able to distinguish between legitimate and illegitimate program requests. It does this by authenticating each request. This prevents programs from taking over the computer.
     • Peripheral Management
       • A peripheral device is hardware that interacts with a computer e.g. keyboard.

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