Software and Shit

• System Software is independent of any General-Purpose Package or any Application Area
• System software is designed to assist the computer in efficient execution of application programs
• System Software:

  1. Library Programs
  2. translation Software
  3. Utility Programs
  4. The OS
• Library Programs are a collection of programs that can be used
• Translation Software convert languages to another language
• There are three types of Translators:

  1. Assemblers
  2. Interpreters
  3. Compilers
• Utility Software is used to maintain the system. e.g. Disk Defragmentation
• The OS is the most important part of the system as it provides a interface for the user, communicates with I/O devices and manages memory
• Direct Addressing is when a memory address is holding a value you use
• Immediate addressing is when you use am actual value
• Assemblers: Translate Assembly language to machine code
• Interpreters take one line at a time and checks to see if it’s valid, then executes that, then moves to the next line
• Interpreter Pros: debugging programs when coding, if an error is found it can be corrected
• Compilers check that all lines are valid, then converts It all so it can be executed by a computer
• Compiler Pros: runs faster, the machine code can be run on a computer without a compiler
• Fetch-Execute Steps (fetch):

  1. Address of next instruction transferred from PC to MAR
  2. PC incremented by 1
  3. Instruction stored in location addressed by MAR is transferred to MBR
  4. Instruction Moved from MBR to CIR
• Fetch-Execute (decode):

  1. Instruction in CIR is decoded
  2. (if required) additional data is fetched from memory
  3. Its passed to the registers
• Fetch-Execute (execute):

  1. Instructions are executed by the ALU
  2. Registers are used to store intermediate data
  3. Result is stored in the general purpose register or memory
• The Processors main bits are:

  • ALU
  • CU
  • Clock
  • PC
  • General Registers
  • MBR
  • MAR and CIR
• Boolean Algebra Laws:

  • A.(B+C) = (A.B)+(A.C)
  • A+(A.C) = (A+B).(A+C)
  • A.A = A = A+A
  • A+NOTA = 1
  • A.NOTA = 0
  • A+(NOTA.B) = A.B
  • A.(NOTA+B) = A+B
  • NOT(A+B) = NOTA.NOTB
  • NOT(A.B) = NOTA+NOTB
  • 1.A = A, 1+A = 1
  • 0.A =0, 0+A=A

  
• What does the ALU do?

  Carries out arithmetic operations