IB Computer Science

• What is the role of the CPU?

  It processes all instructions and executes code.
• What operations does the CPU perform?

  It performs arithmetic, logical, and input/output operations.
• What is the Fetch-Decode-Execute Cycle (FDE Cycle)?

  • Process starts at the Program Counter (PC)
  • PC sends address to Memory Address Register (MAR)
  • MAR sends address to Random Access Memory (RAM), stores result in Memory Data Register (MDR)
  • MDR sends data to Current Instruction Register (CIR) for decoding
  • CIR passes decoded instructions to Arithmetic Logic Unit (ALU)
  • ALU executes instructions and may send further instructions to MAR

  
• Who orchestrates the FDE cycle?

  The Control Unit (CU) orchestrates the FDE cycle.
• What happens when a CPU has 2 cores?

  It has 2 Arithmetic Logic Units (ALUs) for processing.
• How is processor speed measured?

  It is measured by the number of FDE cycles per second.
• What does 2GHz represent?

  It represents 2 billion cycles per second.
• What are the characteristics of Primary Memory (RAM)?

  • Random Access Memory
  • Short term memory
  • Volatile: data lost when computer is turned off
  • Non-persistent storage
• What are the characteristics of Primary Memory (ROM)?

  • Read-only Memory
  • Stores permanent instructions
  • Used to boot the computer (BIOS)
  • Keeps data without electricity

  
• What is the purpose of Cache memory?

  • Stores frequently used instructions from RAM
  • Processor checks cache first
  • Includes L1 (Fastest) and L2 Cache
  • More expensive than RAM
• What is Secondary Memory?

  • Hard Drive
  • Long-term memory
  • Persistent storage
  • Holds data not currently in use
  • Slower and cheaper than primary memory
  • Not directly connected to CPU
  • Much larger amounts of data

  
• What is Virtual Memory?

  • Used when primary memory is overloaded
  • Data sent to secondary memory
  • Slower and temporary
  • Returned to primary memory as needed
  • Stored in units called "pages"
• What is the role of Operating Systems?


  • Controls computer's hardware and resources
  • Provides services for computer programs
  • 5 roles: User interface, Memory Management, Peripheral Management, Multitasking, Security

  
• What are the types of User Interfaces?

  • GUI (Graphical User Interface): menus, point and click
  • CLI (Command Line Interface): type in commands
  • NLI (Natural Language Interface): speak to computer (e.g., Siri)
  • MBI (Menu Based Interface): menu options without commands

  
• What is Memory Management in Operating Systems?

  • Keeps track of storage devices (HDD, Flash Drive)
  • Allocates memory (RAM) to programs
  • Modifies memory locations
  • Sorts data on disk drives and RAM for efficiency
  • Organizes data into folders
  • Copies and deletes files

  
• What is Peripheral Management?

  • Manages peripherals like keyboard, mouse, monitor
  • Coordinates with BIOS (basic input/output system)
  • Uses device drivers to interface with peripherals
  • Device drivers translate peripheral signals

  
• What is Multitasking in Operating Systems?


  • Allocates CPU cycles to concurrent programs based on priority and time
  • Each program gets a slice of time to use CPU
  • Slices vary in length
• What are the security measures in Operating Systems?

  • Username and password
  • User permissions
  • File permissions for reading and writing
• What are examples of Application Software?

  • Word Processors
  • Spreadsheets
  • Database Management System (DBMS) (e.g., MS Access)
  • Email Client (e.g., Outlook)
  • Web Browser
  • Computer Aided Design (CAD)
  • Graphic Processing Software (e.g., Photoshop)

  
• How are images displayed on screens?

  • Displays are divided into pixels
  • Each pixel is the smallest controllable element
  • Each pixel has a different color
  • Color is a combination of red, blue, and green
  • Pixels together display an image
  • Example: 1024x764 screen resolution

  
• What is a pixel?


  A pixel is the smallest controllable element in a display.
• How is color represented in pixels?

  Each color in a pixel is represented by a 6-digit hexadecimal value.
• What do the first two values in a hexadecimal color represent?

  They represent the red component of the color.
• What are Logic Gates?

  • Made up of millions of switches
  • Each takes 1-2 inputs and produces 1 output
  • Possible inputs are 1 (high voltage) or 0 (low voltage)
  • Voltage is the pressure that forces charged electrons to flow through a circuit

  
• What does the Program Counter (PC) hold?

  The memory address of the next instruction to be fetched.
• How is the address from the Program Counter (PC) used in the fetch process?

  It is placed onto the Address Bus.
• What signal does the Control Unit issue during the fetch stage?

  A signal to read from memory via the Control Bus.
• Where is the instruction sent after being read from memory?

  To the Memory Data Register (MDR).
• What happens to the instruction after it is in the Memory Data Register (MDR)?

  It is transferred to the Instruction Register (IR).
• What is the formula for incrementing the Program Counter (PC)?

  PC = PC + 1
• What does the Control Unit (CU) do during the decode stage?

  It reads the instruction in the Instruction Register (IR).
• What components does the instruction get decoded into?

  The opcode and any operands.
• What does the Control Unit prepare for during the decode stage?

  The necessary registers and hardware for execution.
• What does the Control Unit determine during the decode stage?

  If it needs to access the Accumulator (ACC) or other registers, as well as the ALU or memory.
• What does the Control Unit (CU) do during the execute stage?

  It activates the relevant components depending on the type of instruction.
• How does the Control Unit handle a data operation during execution?


  It directs the Arithmetic Logic Unit (ALU) to perform the necessary computation.
• What happens if the instruction is a memory operation?

  The CU sends the appropriate data/address via the Address Bus and Data Bus.
• Where are operands processed during execution?

  In the Accumulator (ACC) or General Purpose Registers (R1, R2, etc.).
• What happens to the result of operations performed by the ALU?

  It is typically stored back in the Accumulator or a general register.
• How is data written to or read from memory during execution?

  Via the Data Bus and the Memory Data Register (MDR).