Computing

Computing

1. Logic gates

   • or, and, not, nand, nor, xor
     • an or gate means that it will turn on if either or both of any inputs are = 1
     • An and gate means that it will turn on of both inputs =1
     • A not gate will turn on if all of the inputs = 0
     • A nand gate will turn on if any inputs = 0
     • A nor gate will turn on if both of the inputs = 0
     • a xor(exclusive or) gate will turn on if only one of the inputs = 1

2. De Morgans law

   • Made of A's and B's
   • + = or, . = and

3. The binary system

   • Binary is made of 1's and 0's which is machine code where 1 is on and 0 is off

4. Half adder

   • The half adder is made up of and xor gate and also an and gate which then gives you a sum(S) and carry(C). The half adder is used to add to binary together

5. Operating System

   • Interactive Operating System – User and computer in direct/two-way communication. User makes input to computer then waits for the output before making next input.
   • Network Operating System – Computer OS is designed primarily to support workstation, personal computer, and, in some instances, older terminal that are connected on a local area network. layers of software that redirects requests to remote resources in a way that is transparent to the user
   • Allocating processor time- The easier way it is managed is each task is given the same, equal amount of processor time This is also known as the ‘round robin’ scheduling. This can be crude as some tasks may need less or no time.
   • Managing Input/Output Devices- The OS also controls the way in which the various input and output devices are allocated, controlled and used by programs that are using them. Allocating print jobs to printer Rendering the windows, frames and dialog boxes to the screen Controlling Read/Write access to the hard disk
   • Memory Management
     • How the OS uses RAM to optimise the performance of the computer
     • The OS controls how the primary memory or RAM is used The OS stores details of all the unallocated locations of memory know as the heap When a user asks for a file to be loaded, it is the job of the memory management routines to check and see if enough memory ismemory and load the file in to those locations. available and then allocate the appropriate
   • Virtual Memory and Paging - An alternative method is to hold kernel or central block of the code in RAM Other sections of the code know as ‘pages’ are loaded from secondary storage as and when they are needed This method allows large applications to run in small sections of RAM, which frees up memory for other applications to run
   • File Management - One of the many tasks the OS has to deal with is file management – this includes controlling the structures that are used to store the files The HDD on a home computer is likely to contain many thousands of files and without some sort of logical structure it would be impossible to be find a specific file amongst so many

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