A02: Fetch, Execution and IO

 The Data is Stored in BITS 

Bits are the smallest unit data measurement.

The bits are stored in binary code (0s and 1s). 

8 bits makes 1 byte.

1 is shown in presence of light and 0 in absence of light.

Functional Unit-

          1. Primary memory or Main memory

• Representation: 2^n (where n= length of the bit and base is used 2 due to usage of binary codes).
  
  2. Cache Memory

• CPU directly interacts with it.
• Access time is more faster in cache memory than in main memory.
• It is of level (example, L1, L2, L3...) and as level of cache increases the size increases and accessibility time decreases. 
  
  3. Register
• Data are frequently executed.
• Accessibility time is faster than the upper two memories.
  
  

Processor 

Arithmetic and Logic Unit : Performs arithmetic and logic operations

Control Unit: Coordinates the operations in memory, ALU and I/O units

Instruction Cycle/ Machine Cycle

• Single cycle of operation
• Operations-

1. Fetch instruction from register
2. Decode the instruction
3. Execute instruction (In ALU)
4. Store or rewrite the result
   
   
   
   
   

Instructions and Programs

• Instruction specifies operation and location of the data.
• The sequence of instructions executed one after another is called program.
• Both instruction and programs are stored in main memory.
• Three instruction types:
1. Load- input devices into processor
2. Store- register to memory
3. Operator- performs the result
   

Processor Component

• Program Counter (PC): Holds the memory address of next instruction
• Instruction register (IR): Holds the current instruction
• General purpose register holds data and addresses.

Handling I/O devices

• Read data
• Write data
• I/O device performs transfer

Programs can be executed quickly by increasing the speed of electronic circuits in processor, decreasing the accessing time in cache and RAM, designing the instruction set (set of instruction understood by the CPU) and through parallelism.

Technology

• The improvement in materials whereby instructions can be executed faster.
• More logic functionality and more storage capacity.

Parallelism 

• It has multicore processor which increases the performance.