The document discusses registers, types of registers, and the system bus. Registers are special high-speed memory units that store data, instructions, and memory addresses. The main registers are the PC, IR, MAR, MDR, ACC, and DR. The system bus connects the CPU, memory, and I/O devices via data lines to transfer data, address lines to designate memory locations, and control lines to manage access to the buses.

1. REGISTERS

2. REGISTERS
 Special purpose high speed temporary memory
units.
 It stores
 Data
 Instructions and
 Address of the memory

3. TYPES OF REGISTERS
 PC
 Holds the address of the next instruction to be executed.
 IR
 Holds the actual instruction which is being currently
executing.
 MAR
 Holds the address part of the current instruction.
 MDR
 Holds the contents of the location whose address is in the
MAR.

4. TYPES OF REGISTERS
 ACC
 Stores data and temporary results.
 DR
 Stores data being transmitted to or from a
peripheral device.

5. SYSTEM BUS
 A bus that connects CPU, memory and I/O
devices .
 Consists of 50-100 separate lines.
 They are categorized into 3
 Data lines
 Address lines
 Control lines

6. DATA LINES
 Provides a path for moving data between
memory & I/O devices.
 Collectively known as data bus.
 Consists of 8,16 and 32 bits separate lines
 Is bidirectional.

7. ADDRESS LINES
 Used to designate the source of data for data
bus.
 They are collectively known as address bus.
 Is unidirectional.

8. CONTROL LINES
 Used to control the access to data and address
bus.
 Collectively known as control bus.
 Is bidirectional.

9. SYSTEM BUS